install: follow unit file symlinks in /usr, but not /etc when looking for [Install] data

Some distributions use alias unit files via symlinks in /usr to cover
for legacy service names. With this change we'll allow "systemctl
enable" on such aliases.

Previously, our rule was that symlinks are user configuration that
"systemctl enable" + "systemctl disable" creates and removes, while unit
files is where the instructions to do so are store. As a result of the
rule we'd never read install information through symlinks, since that
would mix enablement state with installation instructions.

Now, the new rule is that only symlinks inside of /etc are
configuration. Unit files, and symlinks in /usr are now valid for
installation instructions.

This patch is quite a rework of the whole install logic, and makes the
following addional changes:

- Adds a complete test "test-instal-root" that tests the install logic
  pretty comprehensively.

- Never uses canonicalize_file_name(), because that's incompatible with
  operation relative to a specific root directory.

- unit_file_get_state() is reworked to return a proper error, and
  returns the state in a call-by-ref parameter. This cleans up confusion
  between the enum type and errno-like errors.

- The new logic puts a limit on how long to follow unit file symlinks:
  it will do so only for 64 steps at max.

- The InstallContext object's fields are renamed to will_process and
  has_processed (will_install and has_installed) since they are also
  used for deinstallation and all kinds of other operations.

- The root directory is always verified before use.

- install.c is reordered to place the exported functions together.

- Stricter rules are followed when traversing symlinks: the unit suffix
  must say identical, and it's not allowed to link between regular units
  and templated units.

- Various modernizations

- The "invalid" unit file state has been renamed to "bad", in order to
  avoid confusion between UNIT_FILE_INVALID and
  _UNIT_FILE_STATE_INVALID. Given that the state should normally not be
  seen and is not documented this should not be a problematic change.
  The new name is now documented however.

Fixes #1375, #1718, #1706

2 files changed, 1083 insertions, 791 deletions

diff --git a/src/shared/install.c b/src/shared/install.c
index 427e228c9d..17e4ea0b85 100644
--- a/src/shared/install.c
+++ b/src/shared/install.c
@@ -30,6 +30,7 @@
 #include "conf-parser.h"
 #include "dirent-util.h"
 #include "fd-util.h"
+#include "fileio.h"
 #include "fs-util.h"
 #include "hashmap.h"
 #include "install-printf.h"
@@ -46,13 +47,21 @@
 #include "unit-name.h"
 #include "util.h"
 
+#define UNIT_FILE_FOLLOW_SYMLINK_MAX 64
+
+typedef enum SearchFlags {
+        SEARCH_LOAD = 1,
+        SEARCH_FOLLOW_CONFIG_SYMLINKS = 2,
+} SearchFlags;
+
 typedef struct {
-        OrderedHashmap *will_install;
-        OrderedHashmap *have_installed;
+        OrderedHashmap *will_process;
+        OrderedHashmap *have_processed;
 } InstallContext;
 
 static int in_search_path(const char *path, char **search) {
         _cleanup_free_ char *parent = NULL;
+        char **i;
 
         assert(path);
 
@@ -60,7 +69,11 @@ static int in_search_path(const char *path, char **search) {
         if (!parent)
                 return -ENOMEM;
 
-        return strv_contains(search, parent);
+        STRV_FOREACH(i, search)
+                if (path_equal(parent, *i))
+                        return true;
+
+        return false;
 }
 
 static int get_config_path(UnitFileScope scope, bool runtime, const char *root_dir, char **ret) {
@@ -71,6 +84,9 @@ static int get_config_path(UnitFileScope scope, bool runtime, const char *root_d
         assert(scope < _UNIT_FILE_SCOPE_MAX);
         assert(ret);
 
+        /* This determines where we shall create or remove our
+         * installation ("configuration") symlinks */
+
         switch (scope) {
 
         case UNIT_FILE_SYSTEM:
@@ -119,6 +135,185 @@ static int get_config_path(UnitFileScope scope, bool runtime, const char *root_d
         return 0;
 }
 
+static bool is_config_path(UnitFileScope scope, const char *path) {
+        int r;
+
+        assert(scope >= 0);
+        assert(scope < _UNIT_FILE_SCOPE_MAX);
+        assert(path);
+
+        /* Checks whether the specified path is intended for
+         * configuration or is outside of it */
+
+        switch (scope) {
+
+        case UNIT_FILE_SYSTEM:
+        case UNIT_FILE_GLOBAL:
+                return path_startswith(path, "/etc") ||
+                        path_startswith(path, SYSTEM_CONFIG_UNIT_PATH) ||
+                        path_startswith(path, "/run");
+
+
+        case UNIT_FILE_USER: {
+                _cleanup_free_ char *p = NULL;
+
+                r = user_config_home(&p);
+                if (r < 0)
+                        return r;
+                if (r > 0 && path_startswith(path, p))
+                        return true;
+
+                p = mfree(p);
+
+                r = user_runtime_dir(&p);
+                if (r < 0)
+                        return r;
+                if (r > 0 && path_startswith(path, p))
+                        return true;
+
+                return false;
+        }
+
+        default:
+                assert_not_reached("Bad scope");
+        }
+}
+
+
+static int verify_root_dir(UnitFileScope scope, const char **root_dir) {
+        int r;
+
+        assert(root_dir);
+
+        /* Verifies that the specified root directory to operate on
+         * makes sense. Reset it to NULL if it is the root directory
+         * or set to empty */
+
+        if (isempty(*root_dir) || path_equal(*root_dir, "/")) {
+                *root_dir = NULL;
+                return 0;
+        }
+
+        if (scope != UNIT_FILE_SYSTEM)
+                return -EINVAL;
+
+        r = is_dir(*root_dir, true);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTDIR;
+
+        return 0;
+}
+
+int unit_file_changes_add(
+                UnitFileChange **changes,
+                unsigned *n_changes,
+                UnitFileChangeType type,
+                const char *path,
+                const char *source) {
+
+        UnitFileChange *c;
+        unsigned i;
+
+        assert(path);
+        assert(!changes == !n_changes);
+
+        if (!changes)
+                return 0;
+
+        c = realloc(*changes, (*n_changes + 1) * sizeof(UnitFileChange));
+        if (!c)
+                return -ENOMEM;
+
+        *changes = c;
+        i = *n_changes;
+
+        c[i].type = type;
+        c[i].path = strdup(path);
+        if (!c[i].path)
+                return -ENOMEM;
+
+        path_kill_slashes(c[i].path);
+
+        if (source) {
+                c[i].source = strdup(source);
+                if (!c[i].source) {
+                        free(c[i].path);
+                        return -ENOMEM;
+                }
+
+                path_kill_slashes(c[i].path);
+        } else
+                c[i].source = NULL;
+
+        *n_changes = i+1;
+        return 0;
+}
+
+void unit_file_changes_free(UnitFileChange *changes, unsigned n_changes) {
+        unsigned i;
+
+        assert(changes || n_changes == 0);
+
+        if (!changes)
+                return;
+
+        for (i = 0; i < n_changes; i++) {
+                free(changes[i].path);
+                free(changes[i].source);
+        }
+
+        free(changes);
+}
+
+static int create_symlink(
+                const char *old_path,
+                const char *new_path,
+                bool force,
+                UnitFileChange **changes,
+                unsigned *n_changes) {
+
+        _cleanup_free_ char *dest = NULL;
+        int r;
+
+        assert(old_path);
+        assert(new_path);
+
+        /* Actually create a symlink, and remember that we did. Is
+         * smart enough to check if there's already a valid symlink in
+         * place. */
+
+        mkdir_parents_label(new_path, 0755);
+
+        if (symlink(old_path, new_path) >= 0) {
+                unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, new_path, old_path);
+                return 0;
+        }
+
+        if (errno != EEXIST)
+                return -errno;
+
+        r = readlink_malloc(new_path, &dest);
+        if (r < 0)
+                return r;
+
+        if (path_equal(dest, old_path))
+                return 0;
+
+        if (!force)
+                return -EEXIST;
+
+        r = symlink_atomic(old_path, new_path);
+        if (r < 0)
+                return r;
+
+        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, new_path, NULL);
+        unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, new_path, old_path);
+
+        return 0;
+}
+
 static int mark_symlink_for_removal(
                 Set **remove_symlinks_to,
                 const char *p) {
@@ -144,7 +339,7 @@ static int mark_symlink_for_removal(
         if (r < 0)
                 return r;
 
-        return 0;
+        return 1;
 }
 
 static int remove_marked_symlinks_fd(
@@ -152,10 +347,9 @@ static int remove_marked_symlinks_fd(
                 int fd,
                 const char *path,
                 const char *config_path,
-                bool *deleted,
+                bool *restart,
                 UnitFileChange **changes,
-                unsigned *n_changes,
-                char** instance_whitelist) {
+                unsigned *n_changes) {
 
         _cleanup_closedir_ DIR *d = NULL;
         struct dirent *de;
@@ -165,7 +359,7 @@ static int remove_marked_symlinks_fd(
         assert(fd >= 0);
         assert(path);
         assert(config_path);
-        assert(deleted);
+        assert(restart);
 
         d = fdopendir(fd);
         if (!d) {
@@ -200,42 +394,23 @@ static int remove_marked_symlinks_fd(
                         }
 
                         /* This will close nfd, regardless whether it succeeds or not */
-                        q = remove_marked_symlinks_fd(remove_symlinks_to, nfd, p, config_path, deleted, changes, n_changes, instance_whitelist);
+                        q = remove_marked_symlinks_fd(remove_symlinks_to, nfd, p, config_path, restart, changes, n_changes);
                         if (q < 0 && r == 0)
                                 r = q;
 
                 } else if (de->d_type == DT_LNK) {
                         _cleanup_free_ char *p = NULL, *dest = NULL;
-                        int q;
                         bool found;
+                        int q;
 
                         if (!unit_name_is_valid(de->d_name, UNIT_NAME_ANY))
                                 continue;
 
-                        if (unit_name_is_valid(de->d_name, UNIT_NAME_INSTANCE) &&
-                            instance_whitelist &&
-                            !strv_contains(instance_whitelist, de->d_name)) {
-
-                                _cleanup_free_ char *w = NULL;
-
-                                /* OK, the file is not listed directly
-                                 * in the whitelist, so let's check if
-                                 * the template of it might be
-                                 * listed. */
-
-                                r = unit_name_template(de->d_name, &w);
-                                if (r < 0)
-                                        return r;
-
-                                if (!strv_contains(instance_whitelist, w))
-                                        continue;
-                        }
-
                         p = path_make_absolute(de->d_name, path);
                         if (!p)
                                 return -ENOMEM;
 
-                        q = readlink_and_canonicalize(p, &dest);
+                        q = readlink_malloc(p, &dest);
                         if (q < 0) {
                                 if (q == -ENOENT)
                                         continue;
@@ -245,9 +420,15 @@ static int remove_marked_symlinks_fd(
                                 continue;
                         }
 
+                        /* We remove all links pointing to a file or
+                         * path that is marked, as well as all files
+                         * sharing the same name as a file that is
+                         * marked. */
+
                         found =
-                                set_get(remove_symlinks_to, dest) ||
-                                set_get(remove_symlinks_to, basename(dest));
+                                set_contains(remove_symlinks_to, dest) ||
+                                set_contains(remove_symlinks_to, basename(dest)) ||
+                                set_contains(remove_symlinks_to, de->d_name);
 
                         if (!found)
                                 continue;
@@ -259,18 +440,15 @@ static int remove_marked_symlinks_fd(
                         }
 
                         path_kill_slashes(p);
-                        rmdir_parents(p, config_path);
-                        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, p, NULL);
+                        (void) rmdir_parents(p, config_path);
 
-                        if (!set_get(remove_symlinks_to, p)) {
+                        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, p, NULL);
 
-                                q = mark_symlink_for_removal(&remove_symlinks_to, p);
-                                if (q < 0) {
-                                        if (r == 0)
-                                                r = q;
-                                } else
-                                        *deleted = true;
-                        }
+                        q = mark_symlink_for_removal(&remove_symlinks_to, p);
+                        if (q < 0)
+                                return q;
+                        if (q > 0)
+                                *restart = true;
                 }
         }
 
@@ -281,11 +459,10 @@ static int remove_marked_symlinks(
                 Set *remove_symlinks_to,
                 const char *config_path,
                 UnitFileChange **changes,
-                unsigned *n_changes,
-                char** instance_whitelist) {
+                unsigned *n_changes) {
 
         _cleanup_close_ int fd = -1;
-        bool deleted;
+        bool restart;
         int r = 0;
 
         assert(config_path);
@@ -299,22 +476,23 @@ static int remove_marked_symlinks(
 
         do {
                 int q, cfd;
-                deleted = false;
+                restart = false;
 
                 cfd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
                 if (cfd < 0)
                         return -errno;
 
                 /* This takes possession of cfd and closes it */
-                q = remove_marked_symlinks_fd(remove_symlinks_to, cfd, config_path, config_path, &deleted, changes, n_changes, instance_whitelist);
+                q = remove_marked_symlinks_fd(remove_symlinks_to, cfd, config_path, config_path, &restart, changes, n_changes);
                 if (r == 0)
                         r = q;
-        } while (deleted);
+        } while (restart);
 
         return r;
 }
 
 static int find_symlinks_fd(
+                const char *root_dir,
                 const char *name,
                 int fd,
                 const char *path,
@@ -362,7 +540,7 @@ static int find_symlinks_fd(
                         }
 
                         /* This will close nfd, regardless whether it succeeds or not */
-                        q = find_symlinks_fd(name, nfd, p, config_path, same_name_link);
+                        q = find_symlinks_fd(root_dir, name, nfd, p, config_path, same_name_link);
                         if (q > 0)
                                 return 1;
                         if (r == 0)
@@ -379,7 +557,7 @@ static int find_symlinks_fd(
                                 return -ENOMEM;
 
                         /* Acquire symlink destination */
-                        q = readlink_and_canonicalize(p, &dest);
+                        q = readlink_malloc(p, &dest);
                         if (q == -ENOENT)
                                 continue;
                         if (q < 0) {
@@ -388,6 +566,18 @@ static int find_symlinks_fd(
                                 continue;
                         }
 
+                        /* Make absolute */
+                        if (!path_is_absolute(dest)) {
+                                char *x;
+
+                                x = prefix_root(root_dir, dest);
+                                if (!x)
+                                        return -ENOMEM;
+
+                                free(dest);
+                                dest = x;
+                        }
+
                         /* Check if the symlink itself matches what we
                          * are looking for */
                         if (path_is_absolute(name))
@@ -425,6 +615,7 @@ static int find_symlinks_fd(
 }
 
 static int find_symlinks(
+                const char *root_dir,
                 const char *name,
                 const char *config_path,
                 bool *same_name_link) {
@@ -443,7 +634,7 @@ static int find_symlinks(
         }
 
         /* This takes possession of fd and closes it */
-        return find_symlinks_fd(name, fd, config_path, config_path, same_name_link);
+        return find_symlinks_fd(root_dir, name, fd, config_path, config_path, same_name_link);
 }
 
 static int find_symlinks_in_scope(
@@ -452,338 +643,54 @@ static int find_symlinks_in_scope(
                 const char *name,
                 UnitFileState *state) {
 
-        int r;
         _cleanup_free_ char *normal_path = NULL, *runtime_path = NULL;
         bool same_name_link_runtime = false, same_name_link = false;
+        int r;
 
         assert(scope >= 0);
         assert(scope < _UNIT_FILE_SCOPE_MAX);
         assert(name);
 
-        /* First look in runtime config path */
-        r = get_config_path(scope, true, root_dir, &normal_path);
+        /* First look in the normal config path */
+        r = get_config_path(scope, false, root_dir, &normal_path);
         if (r < 0)
                 return r;
 
-        r = find_symlinks(name, normal_path, &same_name_link_runtime);
+        r = find_symlinks(root_dir, name, normal_path, &same_name_link);
         if (r < 0)
                 return r;
-        else if (r > 0) {
-                *state = UNIT_FILE_ENABLED_RUNTIME;
+        if (r > 0) {
+                *state = UNIT_FILE_ENABLED;
                 return r;
         }
 
-        /* Then look in the normal config path */
-        r = get_config_path(scope, false, root_dir, &runtime_path);
+        /* Then look in runtime config path */
+        r = get_config_path(scope, true, root_dir, &runtime_path);
         if (r < 0)
                 return r;
 
-        r = find_symlinks(name, runtime_path, &same_name_link);
+        r = find_symlinks(root_dir, name, runtime_path, &same_name_link_runtime);
         if (r < 0)
                 return r;
-        else if (r > 0) {
-                *state = UNIT_FILE_ENABLED;
+        if (r > 0) {
+                *state = UNIT_FILE_ENABLED_RUNTIME;
                 return r;
         }
 
         /* Hmm, we didn't find it, but maybe we found the same name
          * link? */
-        if (same_name_link_runtime) {
-                *state = UNIT_FILE_LINKED_RUNTIME;
-                return 1;
-        } else if (same_name_link) {
+        if (same_name_link) {
                 *state = UNIT_FILE_LINKED;
                 return 1;
         }
-
-        return 0;
-}
-
-int unit_file_mask(
-                UnitFileScope scope,
-                bool runtime,
-                const char *root_dir,
-                char **files,
-                bool force,
-                UnitFileChange **changes,
-                unsigned *n_changes) {
-
-        _cleanup_free_ char *prefix = NULL;
-        char **i;
-        int r;
-
-        assert(scope >= 0);
-        assert(scope < _UNIT_FILE_SCOPE_MAX);
-
-        r = get_config_path(scope, runtime, root_dir, &prefix);
-        if (r < 0)
-                return r;
-
-        STRV_FOREACH(i, files) {
-                _cleanup_free_ char *path = NULL;
-
-                if (!unit_name_is_valid(*i, UNIT_NAME_ANY)) {
-                        if (r == 0)
-                                r = -EINVAL;
-                        continue;
-                }
-
-                path = path_make_absolute(*i, prefix);
-                if (!path)
-                        return -ENOMEM;
-
-                if (symlink("/dev/null", path) >= 0) {
-                        unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, path, "/dev/null");
-                        continue;
-                }
-
-                if (errno == EEXIST) {
-
-                        if (null_or_empty_path(path) > 0)
-                                continue;
-
-                        if (force) {
-                                if (symlink_atomic("/dev/null", path) >= 0) {
-                                        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, path, NULL);
-                                        unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, path, "/dev/null");
-                                        continue;
-                                }
-                        }
-
-                        if (r == 0)
-                                r = -EEXIST;
-                } else {
-                        if (r == 0)
-                                r = -errno;
-                }
-        }
-
-        return r;
-}
-
-int unit_file_unmask(
-                UnitFileScope scope,
-                bool runtime,
-                const char *root_dir,
-                char **files,
-                UnitFileChange **changes,
-                unsigned *n_changes) {
-
-        _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
-        _cleanup_free_ char *config_path = NULL;
-        char **i;
-        int r, q;
-
-        assert(scope >= 0);
-        assert(scope < _UNIT_FILE_SCOPE_MAX);
-
-        r = get_config_path(scope, runtime, root_dir, &config_path);
-        if (r < 0)
-                return r;
-
-        STRV_FOREACH(i, files) {
-                _cleanup_free_ char *path = NULL;
-
-                if (!unit_name_is_valid(*i, UNIT_NAME_ANY)) {
-                        if (r == 0)
-                                r = -EINVAL;
-                        continue;
-                }
-
-                path = path_make_absolute(*i, config_path);
-                if (!path)
-                        return -ENOMEM;
-
-                q = null_or_empty_path(path);
-                if (q > 0) {
-                        if (unlink(path) < 0)
-                                q = -errno;
-                        else {
-                                q = mark_symlink_for_removal(&remove_symlinks_to, path);
-                                unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, path, NULL);
-                        }
-                }
-
-                if (q != -ENOENT && r == 0)
-                        r = q;
-        }
-
-        q = remove_marked_symlinks(remove_symlinks_to, config_path, changes, n_changes, files);
-        if (r == 0)
-                r = q;
-
-        return r;
-}
-
-int unit_file_link(
-                UnitFileScope scope,
-                bool runtime,
-                const char *root_dir,
-                char **files,
-                bool force,
-                UnitFileChange **changes,
-                unsigned *n_changes) {
-
-        _cleanup_lookup_paths_free_ LookupPaths paths = {};
-        _cleanup_free_ char *config_path = NULL;
-        char **i;
-        int r, q;
-
-        assert(scope >= 0);
-        assert(scope < _UNIT_FILE_SCOPE_MAX);
-
-        r = lookup_paths_init_from_scope(&paths, scope, root_dir);
-        if (r < 0)
-                return r;
-
-        r = get_config_path(scope, runtime, root_dir, &config_path);
-        if (r < 0)
-                return r;
-
-        STRV_FOREACH(i, files) {
-                _cleanup_free_ char *path = NULL;
-                char *fn;
-                struct stat st;
-
-                fn = basename(*i);
-
-                if (!path_is_absolute(*i) ||
-                    !unit_name_is_valid(fn, UNIT_NAME_ANY)) {
-                        if (r == 0)
-                                r = -EINVAL;
-                        continue;
-                }
-
-                if (lstat(*i, &st) < 0) {
-                        if (r == 0)
-                                r = -errno;
-                        continue;
-                }
-
-                if (!S_ISREG(st.st_mode)) {
-                        r = -ENOENT;
-                        continue;
-                }
-
-                q = in_search_path(*i, paths.unit_path);
-                if (q < 0)
-                        return q;
-                if (q > 0)
-                        continue;
-
-                path = path_make_absolute(fn, config_path);
-                if (!path)
-                        return -ENOMEM;
-
-                if (symlink(*i, path) >= 0) {
-                        unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, path, *i);
-                        continue;
-                }
-
-                if (errno == EEXIST) {
-                        _cleanup_free_ char *dest = NULL;
-
-                        q = readlink_and_make_absolute(path, &dest);
-                        if (q < 0 && errno != ENOENT) {
-                                if (r == 0)
-                                        r = q;
-                                continue;
-                        }
-
-                        if (q >= 0 && path_equal(dest, *i))
-                                continue;
-
-                        if (force) {
-                                if (symlink_atomic(*i, path) >= 0) {
-                                        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, path, NULL);
-                                        unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, path, *i);
-                                        continue;
-                                }
-                        }
-
-                        if (r == 0)
-                                r = -EEXIST;
-                } else {
-                        if (r == 0)
-                                r = -errno;
-                }
-        }
-
-        return r;
-}
-
-void unit_file_list_free(Hashmap *h) {
-        UnitFileList *i;
-
-        while ((i = hashmap_steal_first(h))) {
-                free(i->path);
-                free(i);
+        if (same_name_link_runtime) {
+                *state = UNIT_FILE_LINKED_RUNTIME;
+                return 1;
         }
 
-        hashmap_free(h);
-}
-
-int unit_file_changes_add(
-                UnitFileChange **changes,
-                unsigned *n_changes,
-                UnitFileChangeType type,
-                const char *path,
-                const char *source) {
-
-        UnitFileChange *c;
-        unsigned i;
-
-        assert(path);
-        assert(!changes == !n_changes);
-
-        if (!changes)
-                return 0;
-
-        c = realloc(*changes, (*n_changes + 1) * sizeof(UnitFileChange));
-        if (!c)
-                return -ENOMEM;
-
-        *changes = c;
-        i = *n_changes;
-
-        c[i].type = type;
-        c[i].path = strdup(path);
-        if (!c[i].path)
-                return -ENOMEM;
-
-        path_kill_slashes(c[i].path);
-
-        if (source) {
-                c[i].source = strdup(source);
-                if (!c[i].source) {
-                        free(c[i].path);
-                        return -ENOMEM;
-                }
-
-                path_kill_slashes(c[i].path);
-        } else
-                c[i].source = NULL;
-
-        *n_changes = i+1;
         return 0;
 }
 
-void unit_file_changes_free(UnitFileChange *changes, unsigned n_changes) {
-        unsigned i;
-
-        assert(changes || n_changes == 0);
-
-        if (!changes)
-                return;
-
-        for (i = 0; i < n_changes; i++) {
-                free(changes[i].path);
-                free(changes[i].source);
-        }
-
-        free(changes);
-}
-
 static void install_info_free(UnitFileInstallInfo *i) {
 
         if (!i)
@@ -796,34 +703,45 @@ static void install_info_free(UnitFileInstallInfo *i) {
         strv_free(i->required_by);
         strv_free(i->also);
         free(i->default_instance);
+        free(i->symlink_target);
         free(i);
 }
 
-static void install_info_hashmap_free(OrderedHashmap *m) {
+static OrderedHashmap* install_info_hashmap_free(OrderedHashmap *m) {
         UnitFileInstallInfo *i;
 
         if (!m)
-                return;
+                return NULL;
 
         while ((i = ordered_hashmap_steal_first(m)))
                 install_info_free(i);
 
-        ordered_hashmap_free(m);
+        return ordered_hashmap_free(m);
 }
 
 static void install_context_done(InstallContext *c) {
         assert(c);
 
-        install_info_hashmap_free(c->will_install);
-        install_info_hashmap_free(c->have_installed);
+        c->will_process = install_info_hashmap_free(c->will_process);
+        c->have_processed = install_info_hashmap_free(c->have_processed);
+}
+
+static UnitFileInstallInfo *install_info_find(InstallContext *c, const char *name) {
+        UnitFileInstallInfo *i;
 
-        c->will_install = c->have_installed = NULL;
+        i = ordered_hashmap_get(c->have_processed, name);
+        if (i)
+                return i;
+
+        return ordered_hashmap_get(c->will_process, name);
 }
 
 static int install_info_add(
                 InstallContext *c,
                 const char *name,
-                const char *path) {
+                const char *path,
+                UnitFileInstallInfo **ret) {
+
         UnitFileInstallInfo *i = NULL;
         int r;
 
@@ -836,17 +754,21 @@ static int install_info_add(
         if (!unit_name_is_valid(name, UNIT_NAME_ANY))
                 return -EINVAL;
 
-        if (ordered_hashmap_get(c->have_installed, name) ||
-            ordered_hashmap_get(c->will_install, name))
+        i = install_info_find(c, name);
+        if (i) {
+                if (ret)
+                        *ret = i;
                 return 0;
+        }
 
-        r = ordered_hashmap_ensure_allocated(&c->will_install, &string_hash_ops);
+        r = ordered_hashmap_ensure_allocated(&c->will_process, &string_hash_ops);
         if (r < 0)
                 return r;
 
         i = new0(UnitFileInstallInfo, 1);
         if (!i)
                 return -ENOMEM;
+        i->type = _UNIT_FILE_TYPE_INVALID;
 
         i->name = strdup(name);
         if (!i->name) {
@@ -862,10 +784,13 @@ static int install_info_add(
                 }
         }
 
-        r = ordered_hashmap_put(c->will_install, i->name, i);
+        r = ordered_hashmap_put(c->will_process, i->name, i);
         if (r < 0)
                 goto fail;
 
+        if (ret)
+                *ret = i;
+
         return 0;
 
 fail:
@@ -875,15 +800,16 @@ fail:
 
 static int install_info_add_auto(
                 InstallContext *c,
-                const char *name_or_path) {
+                const char *name_or_path,
+                UnitFileInstallInfo **ret) {
 
         assert(c);
         assert(name_or_path);
 
         if (path_is_absolute(name_or_path))
-                return install_info_add(c, NULL, name_or_path);
+                return install_info_add(c, NULL, name_or_path, ret);
         else
-                return install_info_add(c, name_or_path, NULL);
+                return install_info_add(c, name_or_path, NULL, ret);
 }
 
 static int config_parse_also(
@@ -898,33 +824,32 @@ static int config_parse_also(
                 void *data,
                 void *userdata) {
 
-        InstallContext *c = data;
         UnitFileInstallInfo *i = userdata;
+        InstallContext *c = data;
+        int r;
 
         assert(filename);
         assert(lvalue);
         assert(rvalue);
 
-        for(;;) {
-                _cleanup_free_ char *n = NULL;
-                int r;
-
-                r = extract_first_word(&rvalue, &n, NULL, 0);
-                if (r < 0) {
-                        log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse config %s, ignoring.", rvalue);
-                        return 0;
-                }
+        for (;;) {
+                _cleanup_free_ char *word = NULL;
 
+                r = extract_first_word(&rvalue, &word, NULL, 0);
+                if (r < 0)
+                        return r;
                 if (r == 0)
                         break;
 
-                r = install_info_add(c, n, NULL);
+                r = install_info_add(c, word, NULL, NULL);
                 if (r < 0)
                         return r;
 
-                r = strv_extend(&i->also, n);
+                r = strv_push(&i->also, word);
                 if (r < 0)
                         return r;
+
+                word = NULL;
         }
 
         return 0;
@@ -1000,9 +925,7 @@ static int unit_file_load(
                 UnitFileInstallInfo *info,
                 const char *path,
                 const char *root_dir,
-                bool allow_symlink,
-                bool load,
-                bool *also) {
+                SearchFlags flags) {
 
         const ConfigTableItem items[] = {
                 { "Install", "Alias",           config_parse_strv,             0, &info->aliases           },
@@ -1015,7 +938,9 @@ static int unit_file_load(
         };
 
         _cleanup_fclose_ FILE *f = NULL;
-        int fd, r;
+        _cleanup_close_ int fd = -1;
+        struct stat st;
+        int r;
 
         assert(c);
         assert(info);
@@ -1023,22 +948,43 @@ static int unit_file_load(
 
         path = prefix_roota(root_dir, path);
 
-        if (!load) {
-                if (access(path, F_OK) < 0)
+        if (!(flags & SEARCH_LOAD)) {
+                r = lstat(path, &st);
+                if (r < 0)
                         return -errno;
 
+                if (null_or_empty(&st))
+                        info->type = UNIT_FILE_TYPE_MASKED;
+                else if (S_ISREG(st.st_mode))
+                        info->type = UNIT_FILE_TYPE_REGULAR;
+                else if (S_ISLNK(st.st_mode))
+                        return -ELOOP;
+                else if (S_ISDIR(st.st_mode))
+                        return -EISDIR;
+                else
+                        return -ENOTTY;
+
                 return 0;
         }
 
-        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|(allow_symlink ? 0 : O_NOFOLLOW));
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
         if (fd < 0)
                 return -errno;
+        if (fstat(fd, &st) < 0)
+                return -errno;
+        if (null_or_empty(&st)) {
+                info->type = UNIT_FILE_MASKED;
+                return 0;
+        }
+        if (S_ISDIR(st.st_mode))
+                return -EISDIR;
+        if (!S_ISREG(st.st_mode))
+                return -ENOTTY;
 
         f = fdopen(fd, "re");
-        if (!f) {
-                safe_close(fd);
-                return -ENOMEM;
-        }
+        if (!f)
+                return -errno;
+        fd = -1;
 
         r = config_parse(NULL, path, f,
                          NULL,
@@ -1047,8 +993,7 @@ static int unit_file_load(
         if (r < 0)
                 return r;
 
-        if (also)
-                *also = !strv_isempty(info->also);
+        info->type = UNIT_FILE_TYPE_REGULAR;
 
         return
                 (int) strv_length(info->aliases) +
@@ -1056,14 +1001,73 @@ static int unit_file_load(
                 (int) strv_length(info->required_by);
 }
 
+static int unit_file_load_or_readlink(
+                InstallContext *c,
+                UnitFileInstallInfo *info,
+                const char *path,
+                const char *root_dir,
+                SearchFlags flags) {
+
+        _cleanup_free_ char *np = NULL;
+        int r;
+
+        r = unit_file_load(c, info, path, root_dir, flags);
+        if (r != -ELOOP)
+                return r;
+
+        /* This is a symlink, let's read it. */
+
+        r = readlink_and_make_absolute_root(root_dir, path, &np);
+        if (r < 0)
+                return r;
+
+        if (path_equal(np, "/dev/null"))
+                info->type = UNIT_FILE_TYPE_MASKED;
+        else {
+                const char *bn;
+                UnitType a, b;
+
+                bn = basename(np);
+
+                if (unit_name_is_valid(info->name, UNIT_NAME_PLAIN)) {
+
+                        if (!unit_name_is_valid(bn, UNIT_NAME_PLAIN))
+                                return -EINVAL;
+
+                } else if (unit_name_is_valid(info->name, UNIT_NAME_INSTANCE)) {
+
+                        if (!unit_name_is_valid(bn, UNIT_NAME_INSTANCE|UNIT_NAME_TEMPLATE))
+                                return -EINVAL;
+
+                } else if (unit_name_is_valid(info->name, UNIT_NAME_TEMPLATE)) {
+
+                        if (!unit_name_is_valid(bn, UNIT_NAME_TEMPLATE))
+                                return -EINVAL;
+                } else
+                        return -EINVAL;
+
+                /* Enforce that the symlink destination does not
+                 * change the unit file type. */
+
+                a = unit_name_to_type(info->name);
+                b = unit_name_to_type(bn);
+                if (a < 0 || b < 0 || a != b)
+                        return -EINVAL;
+
+                info->type = UNIT_FILE_TYPE_SYMLINK;
+                info->symlink_target = np;
+                np = NULL;
+        }
+
+        return 0;
+}
+
 static int unit_file_search(
                 InstallContext *c,
                 UnitFileInstallInfo *info,
                 const LookupPaths *paths,
                 const char *root_dir,
-                bool allow_symlink,
-                bool load,
-                bool *also) {
+                SearchFlags flags) {
 
         char **p;
         int r;
@@ -1072,8 +1076,12 @@ static int unit_file_search(
         assert(info);
         assert(paths);
 
+        /* Was this unit already loaded? */
+        if (info->type != _UNIT_FILE_TYPE_INVALID)
+                return 0;
+
         if (info->path)
-                return unit_file_load(c, info, info->path, root_dir, allow_symlink, load, also);
+                return unit_file_load_or_readlink(c, info, info->path, root_dir, flags);
 
         assert(info->name);
 
@@ -1084,14 +1092,15 @@ static int unit_file_search(
                 if (!path)
                         return -ENOMEM;
 
-                r = unit_file_load(c, info, path, root_dir, allow_symlink, load, also);
-                if (r >= 0) {
+                r = unit_file_load_or_readlink(c, info, path, root_dir, flags);
+                if (r < 0) {
+                        if (r != -ENOENT)
+                                return r;
+                } else {
                         info->path = path;
                         path = NULL;
                         return r;
                 }
-                if (r != -ENOENT && r != -ELOOP)
-                        return r;
         }
 
         if (unit_name_is_valid(info->name, UNIT_NAME_INSTANCE)) {
@@ -1113,92 +1122,149 @@ static int unit_file_search(
                         if (!path)
                                 return -ENOMEM;
 
-                        r = unit_file_load(c, info, path, root_dir, allow_symlink, load, also);
-                        if (r >= 0) {
+                        r = unit_file_load_or_readlink(c, info, path, root_dir, flags);
+                        if (r < 0) {
+                                if (r != -ENOENT)
+                                        return r;
+                        } else {
                                 info->path = path;
                                 path = NULL;
                                 return r;
                         }
-                        if (r != -ENOENT && r != -ELOOP)
-                                return r;
                 }
         }
 
         return -ENOENT;
 }
 
-static int unit_file_can_install(
-                const LookupPaths *paths,
+static int install_info_follow(
+                InstallContext *c,
+                UnitFileInstallInfo *i,
                 const char *root_dir,
-                const char *name,
-                bool allow_symlink,
-                bool *also) {
+                SearchFlags flags) {
+
+        assert(c);
+        assert(i);
+
+        if (i->type != UNIT_FILE_TYPE_SYMLINK)
+                return -EINVAL;
+        if (!i->symlink_target)
+                return -EINVAL;
+
+        /* If the basename doesn't match, the caller should add a
+         * complete new entry for this. */
+
+        if (!streq(basename(i->symlink_target), i->name))
+                return -EXDEV;
+
+        free(i->path);
+        i->path = i->symlink_target;
+        i->symlink_target = NULL;
+        i->type = _UNIT_FILE_TYPE_INVALID;
+
+        return unit_file_load_or_readlink(c, i, i->path, root_dir, flags);
+}
+
+static int install_info_traverse(
+                UnitFileScope scope,
+                InstallContext *c,
+                const char *root_dir,
+                const LookupPaths *paths,
+                UnitFileInstallInfo *start,
+                SearchFlags flags,
+                UnitFileInstallInfo **ret) {
 
-        _cleanup_(install_context_done) InstallContext c = {};
         UnitFileInstallInfo *i;
+        unsigned k = 0;
         int r;
 
         assert(paths);
-        assert(name);
+        assert(start);
+        assert(c);
 
-        r = install_info_add_auto(&c, name);
+        r = unit_file_search(c, start, paths, root_dir, flags);
         if (r < 0)
                 return r;
 
-        assert_se(i = ordered_hashmap_first(c.will_install));
+        i = start;
+        while (i->type == UNIT_FILE_TYPE_SYMLINK) {
+                /* Follow the symlink */
 
-        r = unit_file_search(&c, i, paths, root_dir, allow_symlink, true, also);
+                if (++k > UNIT_FILE_FOLLOW_SYMLINK_MAX)
+                        return -ELOOP;
 
-        if (r >= 0)
-                r =
-                        (int) strv_length(i->aliases) +
-                        (int) strv_length(i->wanted_by) +
-                        (int) strv_length(i->required_by);
+                if (!(flags & SEARCH_FOLLOW_CONFIG_SYMLINKS) && is_config_path(scope, i->path))
+                        return -ELOOP;
 
-        return r;
-}
+                r = install_info_follow(c, i, root_dir, flags);
+                if (r < 0) {
+                        _cleanup_free_ char *buffer = NULL;
+                        const char *bn;
 
-static int create_symlink(
-                const char *old_path,
-                const char *new_path,
-                bool force,
-                UnitFileChange **changes,
-                unsigned *n_changes) {
+                        if (r != -EXDEV)
+                                return r;
 
-        _cleanup_free_ char *dest = NULL;
-        int r;
+                        /* Target has a different name, create a new
+                         * install info object for that, and continue
+                         * with that. */
 
-        assert(old_path);
-        assert(new_path);
+                        bn = basename(i->symlink_target);
 
-        mkdir_parents_label(new_path, 0755);
+                        if (unit_name_is_valid(i->name, UNIT_NAME_INSTANCE) &&
+                            unit_name_is_valid(bn, UNIT_NAME_TEMPLATE)) {
 
-        if (symlink(old_path, new_path) >= 0) {
-                unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, new_path, old_path);
-                return 0;
+                                _cleanup_free_ char *instance = NULL;
+
+                                r = unit_name_to_instance(i->name, &instance);
+                                if (r < 0)
+                                        return r;
+
+                                r = unit_name_replace_instance(bn, instance, &buffer);
+                                if (r < 0)
+                                        return r;
+
+                                bn = buffer;
+                        }
+
+                        r = install_info_add(c, bn, NULL, &i);
+                        if (r < 0)
+                                return r;
+
+                        r = unit_file_search(c, i, paths, root_dir, flags);
+                        if (r < 0)
+                                return r;
+                }
+
+                /* Try again, with the new target we found. */
         }
 
-        if (errno != EEXIST)
-                return -errno;
+        if (ret)
+                *ret = i;
 
-        r = readlink_and_make_absolute(new_path, &dest);
-        if (r < 0)
-                return r;
+        return 0;
+}
 
-        if (path_equal(dest, old_path))
-                return 0;
+static int install_info_discover(
+                UnitFileScope scope,
+                InstallContext *c,
+                const char *root_dir,
+                const LookupPaths *paths,
+                const char *name,
+                SearchFlags flags,
+                UnitFileInstallInfo **ret) {
 
-        if (!force)
-                return -EEXIST;
+        UnitFileInstallInfo *i;
+        int r;
 
-        r = symlink_atomic(old_path, new_path);
+        assert(c);
+        assert(paths);
+        assert(name);
+
+        r = install_info_add_auto(c, name, &i);
         if (r < 0)
                 return r;
 
-        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, new_path, NULL);
-        unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, new_path, old_path);
-
-        return 0;
+        return install_info_traverse(scope, c, root_dir, paths, i, flags, ret);
 }
 
 static int install_info_symlink_alias(
@@ -1333,6 +1399,9 @@ static int install_info_apply(
         assert(paths);
         assert(config_path);
 
+        if (i->type != UNIT_FILE_TYPE_REGULAR)
+                return 0;
+
         r = install_info_symlink_alias(i, config_path, force, changes, n_changes);
 
         q = install_info_symlink_wants(i, config_path, i->wanted_by, ".wants/", force, changes, n_changes);
@@ -1351,50 +1420,59 @@ static int install_info_apply(
 }
 
 static int install_context_apply(
+                UnitFileScope scope,
                 InstallContext *c,
                 const LookupPaths *paths,
                 const char *config_path,
                 const char *root_dir,
                 bool force,
+                SearchFlags flags,
                 UnitFileChange **changes,
                 unsigned *n_changes) {
 
         UnitFileInstallInfo *i;
-        int r, q;
+        int r;
 
         assert(c);
         assert(paths);
         assert(config_path);
 
-        if (ordered_hashmap_isempty(c->will_install))
+        if (ordered_hashmap_isempty(c->will_process))
                 return 0;
 
-        r = ordered_hashmap_ensure_allocated(&c->have_installed, &string_hash_ops);
+        r = ordered_hashmap_ensure_allocated(&c->have_processed, &string_hash_ops);
         if (r < 0)
                 return r;
 
         r = 0;
-        while ((i = ordered_hashmap_first(c->will_install))) {
-                assert_se(ordered_hashmap_move_one(c->have_installed, c->will_install, i->name) == 0);
+        while ((i = ordered_hashmap_first(c->will_process))) {
+                int q;
 
-                q = unit_file_search(c, i, paths, root_dir, false, true, NULL);
-                if (q < 0) {
-                        if (r >= 0)
-                                r = q;
+                q = ordered_hashmap_move_one(c->have_processed, c->will_process, i->name);
+                if (q < 0)
+                        return q;
 
+                r = install_info_traverse(scope, c, root_dir, paths, i, flags, NULL);
+                if (r < 0)
                         return r;
-                } else if (r >= 0)
-                        r += q;
+
+                if (i->type != UNIT_FILE_TYPE_REGULAR)
+                        continue;
 
                 q = install_info_apply(i, paths, config_path, root_dir, force, changes, n_changes);
-                if (r >= 0 && q < 0)
-                        r = q;
+                if (r >= 0) {
+                        if (q < 0)
+                                r = q;
+                        else
+                                r+= q;
+                }
         }
 
         return r;
 }
 
 static int install_context_mark_for_removal(
+                UnitFileScope scope,
                 InstallContext *c,
                 const LookupPaths *paths,
                 Set **remove_symlinks_to,
@@ -1402,7 +1480,7 @@ static int install_context_mark_for_removal(
                 const char *root_dir) {
 
         UnitFileInstallInfo *i;
-        int r, q;
+        int r;
 
         assert(c);
         assert(paths);
@@ -1410,84 +1488,182 @@ static int install_context_mark_for_removal(
 
         /* Marks all items for removal */
 
-        if (ordered_hashmap_isempty(c->will_install))
+        if (ordered_hashmap_isempty(c->will_process))
                 return 0;
 
-        r = ordered_hashmap_ensure_allocated(&c->have_installed, &string_hash_ops);
+        r = ordered_hashmap_ensure_allocated(&c->have_processed, &string_hash_ops);
         if (r < 0)
                 return r;
 
-        r = 0;
-        while ((i = ordered_hashmap_first(c->will_install))) {
-                assert_se(ordered_hashmap_move_one(c->have_installed, c->will_install, i->name) == 0);
-
-                q = unit_file_search(c, i, paths, root_dir, false, true, NULL);
-                if (q == -ENOENT) {
-                        /* do nothing */
-                } else if (q < 0) {
-                        if (r >= 0)
-                                r = q;
+        while ((i = ordered_hashmap_first(c->will_process))) {
 
+                r = ordered_hashmap_move_one(c->have_processed, c->will_process, i->name);
+                if (r < 0)
                         return r;
-                } else if (r >= 0)
-                        r += q;
-
-                if (unit_name_is_valid(i->name, UNIT_NAME_INSTANCE)) {
-                        char *unit_file;
-
-                        if (i->path) {
-                                unit_file = basename(i->path);
-
-                                if (unit_name_is_valid(unit_file, UNIT_NAME_INSTANCE))
-                                        /* unit file named as instance exists, thus all symlinks
-                                         * pointing to it will be removed */
-                                        q = mark_symlink_for_removal(remove_symlinks_to, i->name);
-                                else
-                                        /* does not exist, thus we will mark for removal symlinks
-                                         * to template unit file */
-                                        q = mark_symlink_for_removal(remove_symlinks_to, unit_file);
-                        } else {
-                                /* If i->path is not set, it means that we didn't actually find
-                                 * the unit file. But we can still remove symlinks to the
-                                 * nonexistent template. */
-                                r = unit_name_template(i->name, &unit_file);
-                                if (r < 0)
-                                        return r;
 
-                                q = mark_symlink_for_removal(remove_symlinks_to, unit_file);
-                                free(unit_file);
-                        }
-                } else
-                        q = mark_symlink_for_removal(remove_symlinks_to, i->name);
+                r = install_info_traverse(scope, c, root_dir, paths, i, SEARCH_LOAD|SEARCH_FOLLOW_CONFIG_SYMLINKS, NULL);
+                if (r < 0)
+                        return r;
 
-                if (r >= 0 && q < 0)
+                if (i->type != UNIT_FILE_TYPE_REGULAR)
+                        continue;
+
+                r = mark_symlink_for_removal(remove_symlinks_to, i->name);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int unit_file_mask(
+                UnitFileScope scope,
+                bool runtime,
+                const char *root_dir,
+                char **files,
+                bool force,
+                UnitFileChange **changes,
+                unsigned *n_changes) {
+
+        _cleanup_free_ char *prefix = NULL;
+        char **i;
+        int r;
+
+        assert(scope >= 0);
+        assert(scope < _UNIT_FILE_SCOPE_MAX);
+
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
+
+        r = get_config_path(scope, runtime, root_dir, &prefix);
+        if (r < 0)
+                return r;
+
+        STRV_FOREACH(i, files) {
+                _cleanup_free_ char *path = NULL;
+                int q;
+
+                if (!unit_name_is_valid(*i, UNIT_NAME_ANY)) {
+                        if (r == 0)
+                                r = -EINVAL;
+                        continue;
+                }
+
+                path = path_make_absolute(*i, prefix);
+                if (!path)
+                        return -ENOMEM;
+
+                q = create_symlink("/dev/null", path, force, changes, n_changes);
+                if (q < 0 && r >= 0)
                         r = q;
         }
 
         return r;
 }
 
-int unit_file_add_dependency(
+int unit_file_unmask(
+                UnitFileScope scope,
+                bool runtime,
+                const char *root_dir,
+                char **files,
+                UnitFileChange **changes,
+                unsigned *n_changes) {
+
+        _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
+        _cleanup_free_ char *config_path = NULL;
+        _cleanup_free_ char **todo = NULL;
+        size_t n_todo = 0, n_allocated = 0;
+        char **i;
+        int r, q;
+
+        assert(scope >= 0);
+        assert(scope < _UNIT_FILE_SCOPE_MAX);
+
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
+
+        r = get_config_path(scope, runtime, root_dir, &config_path);
+        if (r < 0)
+                return r;
+
+        STRV_FOREACH(i, files) {
+                _cleanup_free_ char *path = NULL;
+
+                if (!unit_name_is_valid(*i, UNIT_NAME_ANY))
+                        return -EINVAL;
+
+                path = path_make_absolute(*i, config_path);
+                if (!path)
+                        return -ENOMEM;
+
+                r = null_or_empty_path(path);
+                if (r == -ENOENT)
+                        continue;
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        continue;
+
+                if (!GREEDY_REALLOC0(todo, n_allocated, n_todo + 2))
+                        return -ENOMEM;
+
+                todo[n_todo++] = *i;
+        }
+
+        strv_uniq(todo);
+
+        r = 0;
+        STRV_FOREACH(i, todo) {
+                _cleanup_free_ char *path = NULL;
+
+                path = path_make_absolute(*i, config_path);
+                if (!path)
+                        return -ENOMEM;
+
+                if (unlink(path) < 0) {
+                        if (errno != -ENOENT && r >= 0)
+                                r = -errno;
+                } else {
+                        q = mark_symlink_for_removal(&remove_symlinks_to, path);
+                        if (q < 0)
+                                return q;
+
+                        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, path, NULL);
+                }
+        }
+
+        q = remove_marked_symlinks(remove_symlinks_to, config_path, changes, n_changes);
+        if (r >= 0)
+                r = q;
+
+        return r;
+}
+
+int unit_file_link(
                 UnitFileScope scope,
                 bool runtime,
                 const char *root_dir,
                 char **files,
-                char *target,
-                UnitDependency dep,
                 bool force,
                 UnitFileChange **changes,
                 unsigned *n_changes) {
 
         _cleanup_lookup_paths_free_ LookupPaths paths = {};
-        _cleanup_(install_context_done) InstallContext c = {};
         _cleanup_free_ char *config_path = NULL;
+        _cleanup_free_ char **todo = NULL;
+        size_t n_todo = 0, n_allocated = 0;
         char **i;
-        int r;
-        UnitFileInstallInfo *info;
+        int r, q;
 
         assert(scope >= 0);
         assert(scope < _UNIT_FILE_SCOPE_MAX);
 
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
+
         r = lookup_paths_init_from_scope(&paths, scope, root_dir);
         if (r < 0)
                 return r;
@@ -1497,52 +1673,135 @@ int unit_file_add_dependency(
                 return r;
 
         STRV_FOREACH(i, files) {
-                UnitFileState state;
+                _cleanup_free_ char *full = NULL;
+                struct stat st;
+                char *fn;
 
-                state = unit_file_get_state(scope, root_dir, *i);
-                if (state < 0)
-                        return state;
-                if (IN_SET(state, UNIT_FILE_MASKED, UNIT_FILE_MASKED_RUNTIME))
-                        return -ESHUTDOWN;
+                if (!path_is_absolute(*i))
+                        return -EINVAL;
 
-                r = install_info_add_auto(&c, *i);
-                if (r < 0)
-                        return r;
+                fn = basename(*i);
+                if (!unit_name_is_valid(fn, UNIT_NAME_ANY))
+                        return -EINVAL;
+
+                full = prefix_root(root_dir, *i);
+                if (!full)
+                        return -ENOMEM;
+
+                if (lstat(full, &st) < 0)
+                        return -errno;
+                if (S_ISLNK(st.st_mode))
+                        return -ELOOP;
+                if (S_ISDIR(st.st_mode))
+                        return -EISDIR;
+                if (!S_ISREG(st.st_mode))
+                        return -ENOTTY;
+
+                q = in_search_path(*i, paths.unit_path);
+                if (q < 0)
+                        return q;
+                if (q > 0)
+                        continue;
+
+                if (!GREEDY_REALLOC0(todo, n_allocated, n_todo + 2))
+                        return -ENOMEM;
+
+                todo[n_todo++] = *i;
         }
 
-        if (!ordered_hashmap_isempty(c.will_install)) {
-                r = ordered_hashmap_ensure_allocated(&c.have_installed, &string_hash_ops);
-                if (r < 0)
-                        return r;
+        strv_uniq(todo);
 
-                r = ordered_hashmap_reserve(c.have_installed, ordered_hashmap_size(c.will_install));
-                if (r < 0)
-                        return r;
+        r = 0;
+        STRV_FOREACH(i, todo) {
+                _cleanup_free_ char *path = NULL;
+
+                path = path_make_absolute(basename(*i), config_path);
+                if (!path)
+                        return -ENOMEM;
+
+                q = create_symlink(*i, path, force, changes, n_changes);
+                if (q < 0 && r >= 0)
+                        r = q;
         }
 
-        while ((info = ordered_hashmap_first(c.will_install))) {
-                assert_se(ordered_hashmap_move_one(c.have_installed, c.will_install, info->name) == 0);
+        return r;
+}
+
+int unit_file_add_dependency(
+                UnitFileScope scope,
+                bool runtime,
+                const char *root_dir,
+                char **files,
+                const char *target,
+                UnitDependency dep,
+                bool force,
+                UnitFileChange **changes,
+                unsigned *n_changes) {
+
+        _cleanup_lookup_paths_free_ LookupPaths paths = {};
+        _cleanup_(install_context_done) InstallContext c = {};
+        _cleanup_free_ char *config_path = NULL;
+        UnitFileInstallInfo *i, *target_info;
+        char **f;
+        int r;
+
+        assert(scope >= 0);
+        assert(scope < _UNIT_FILE_SCOPE_MAX);
+        assert(target);
+
+        if (!IN_SET(dep, UNIT_WANTS, UNIT_REQUIRES))
+                return -EINVAL;
+
+        if (!unit_name_is_valid(target, UNIT_NAME_ANY))
+                return -EINVAL;
+
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
+
+        r = lookup_paths_init_from_scope(&paths, scope, root_dir);
+        if (r < 0)
+                return r;
+
+        r = get_config_path(scope, runtime, root_dir, &config_path);
+        if (r < 0)
+                return r;
+
+        r = install_info_discover(scope, &c, root_dir, &paths, target, SEARCH_FOLLOW_CONFIG_SYMLINKS, &target_info);
+        if (r < 0)
+                return r;
+        if (target_info->type == UNIT_FILE_TYPE_MASKED)
+                return -ESHUTDOWN;
+
+        assert(target_info->type == UNIT_FILE_TYPE_REGULAR);
+
+        STRV_FOREACH(f, files) {
+                char ***l;
 
-                r = unit_file_search(&c, info, &paths, root_dir, false, false, NULL);
+                r = install_info_discover(scope, &c, root_dir, &paths, *f, SEARCH_FOLLOW_CONFIG_SYMLINKS, &i);
                 if (r < 0)
                         return r;
+                if (i->type == UNIT_FILE_TYPE_MASKED)
+                        return -ESHUTDOWN;
+
+                assert(i->type == UNIT_FILE_TYPE_REGULAR);
+
+                /* We didn't actually load anything from the unit
+                 * file, but instead just add in our new symlink to
+                 * create. */
 
                 if (dep == UNIT_WANTS)
-                        r = strv_extend(&info->wanted_by, target);
-                else if (dep == UNIT_REQUIRES)
-                        r = strv_extend(&info->required_by, target);
+                        l = &i->wanted_by;
                 else
-                        r = -EINVAL;
+                        l = &i->required_by;
 
-                if (r < 0)
-                        return r;
-
-                r = install_info_apply(info, &paths, config_path, root_dir, force, changes, n_changes);
-                if (r < 0)
-                        return r;
+                strv_free(*l);
+                *l = strv_new(target_info->name, NULL);
+                if (!*l)
+                        return -ENOMEM;
         }
 
-        return 0;
+        return install_context_apply(scope, &c, &paths, config_path, root_dir, force, SEARCH_FOLLOW_CONFIG_SYMLINKS, changes, n_changes);
 }
 
 int unit_file_enable(
@@ -1556,13 +1815,18 @@ int unit_file_enable(
 
         _cleanup_lookup_paths_free_ LookupPaths paths = {};
         _cleanup_(install_context_done) InstallContext c = {};
-        char **i;
         _cleanup_free_ char *config_path = NULL;
+        UnitFileInstallInfo *i;
+        char **f;
         int r;
 
         assert(scope >= 0);
         assert(scope < _UNIT_FILE_SCOPE_MAX);
 
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
+
         r = lookup_paths_init_from_scope(&paths, scope, root_dir);
         if (r < 0)
                 return r;
@@ -1571,18 +1835,14 @@ int unit_file_enable(
         if (r < 0)
                 return r;
 
-        STRV_FOREACH(i, files) {
-                UnitFileState state;
-
-                state = unit_file_get_state(scope, root_dir, *i);
-                if (state < 0)
-                        return state;
-                if (IN_SET(state, UNIT_FILE_MASKED, UNIT_FILE_MASKED_RUNTIME))
-                        return -ESHUTDOWN;
-
-                r = install_info_add_auto(&c, *i);
+        STRV_FOREACH(f, files) {
+                r = install_info_discover(scope, &c, root_dir, &paths, *f, SEARCH_LOAD, &i);
                 if (r < 0)
                         return r;
+                if (i->type == UNIT_FILE_TYPE_MASKED)
+                        return -ESHUTDOWN;
+
+                assert(i->type == UNIT_FILE_TYPE_REGULAR);
         }
 
         /* This will return the number of symlink rules that were
@@ -1590,7 +1850,7 @@ int unit_file_enable(
            is useful to determine whether the passed files had any
            installation data at all. */
 
-        return install_context_apply(&c, &paths, config_path, root_dir, force, changes, n_changes);
+        return install_context_apply(scope, &c, &paths, config_path, root_dir, force, SEARCH_LOAD, changes, n_changes);
 }
 
 int unit_file_disable(
@@ -1603,14 +1863,18 @@ int unit_file_disable(
 
         _cleanup_lookup_paths_free_ LookupPaths paths = {};
         _cleanup_(install_context_done) InstallContext c = {};
-        char **i;
         _cleanup_free_ char *config_path = NULL;
         _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
-        int r, q;
+        char **i;
+        int r;
 
         assert(scope >= 0);
         assert(scope < _UNIT_FILE_SCOPE_MAX);
 
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
+
         r = lookup_paths_init_from_scope(&paths, scope, root_dir);
         if (r < 0)
                 return r;
@@ -1620,18 +1884,19 @@ int unit_file_disable(
                 return r;
 
         STRV_FOREACH(i, files) {
-                r = install_info_add_auto(&c, *i);
+                if (!unit_name_is_valid(*i, UNIT_NAME_ANY))
+                        return -EINVAL;
+
+                r = install_info_add(&c, *i, NULL, NULL);
                 if (r < 0)
                         return r;
         }
 
-        r = install_context_mark_for_removal(&c, &paths, &remove_symlinks_to, config_path, root_dir);
-
-        q = remove_marked_symlinks(remove_symlinks_to, config_path, changes, n_changes, files);
-        if (r >= 0)
-                r = q;
+        r = install_context_mark_for_removal(scope, &c, &paths, &remove_symlinks_to, config_path, root_dir);
+        if (r < 0)
+                return r;
 
-        return r;
+        return remove_marked_symlinks(remove_symlinks_to, config_path, changes, n_changes);
 }
 
 int unit_file_reenable(
@@ -1642,19 +1907,30 @@ int unit_file_reenable(
                 bool force,
                 UnitFileChange **changes,
                 unsigned *n_changes) {
+
+        char **n;
         int r;
+        size_t l, i;
+
+        /* First, we invoke the disable command with only the basename... */
+        l = strv_length(files);
+        n = newa(char*, l+1);
+        for (i = 0; i < l; i++)
+                n[i] = basename(files[i]);
+        n[i] = NULL;
 
-        r = unit_file_disable(scope, runtime, root_dir, files, changes, n_changes);
+        r = unit_file_disable(scope, runtime, root_dir, n, changes, n_changes);
         if (r < 0)
                 return r;
 
+        /* But the enable command with the full name */
         return unit_file_enable(scope, runtime, root_dir, files, force, changes, n_changes);
 }
 
 int unit_file_set_default(
                 UnitFileScope scope,
                 const char *root_dir,
-                const char *file,
+                const char *name,
                 bool force,
                 UnitFileChange **changes,
                 unsigned *n_changes) {
@@ -1662,42 +1938,40 @@ int unit_file_set_default(
         _cleanup_lookup_paths_free_ LookupPaths paths = {};
         _cleanup_(install_context_done) InstallContext c = {};
         _cleanup_free_ char *config_path = NULL;
-        char *path;
+        UnitFileInstallInfo *i;
+        const char *path;
         int r;
-        UnitFileInstallInfo *i = NULL;
 
         assert(scope >= 0);
         assert(scope < _UNIT_FILE_SCOPE_MAX);
-        assert(file);
+        assert(name);
 
-        if (unit_name_to_type(file) != UNIT_TARGET)
+        if (unit_name_to_type(name) != UNIT_TARGET)
+                return -EINVAL;
+        if (streq(name, SPECIAL_DEFAULT_TARGET))
                 return -EINVAL;
 
-        r = lookup_paths_init_from_scope(&paths, scope, root_dir);
+        r = verify_root_dir(scope, &root_dir);
         if (r < 0)
                 return r;
 
-        r = get_config_path(scope, false, root_dir, &config_path);
+        r = lookup_paths_init_from_scope(&paths, scope, root_dir);
         if (r < 0)
                 return r;
 
-        r = install_info_add_auto(&c, file);
+        r = get_config_path(scope, false, root_dir, &config_path);
         if (r < 0)
                 return r;
 
-        assert_se(i = ordered_hashmap_first(c.will_install));
-
-        r = unit_file_search(&c, i, &paths, root_dir, false, true, NULL);
+        r = install_info_discover(scope, &c, root_dir, &paths, name, 0, &i);
         if (r < 0)
                 return r;
+        if (i->type == UNIT_FILE_TYPE_MASKED)
+                return -ESHUTDOWN;
 
         path = strjoina(config_path, "/" SPECIAL_DEFAULT_TARGET);
 
-        r = create_symlink(i->path, path, force, changes, n_changes);
-        if (r < 0)
-                return r;
-
-        return 0;
+        return create_symlink(i->path, path, force, changes, n_changes);
 }
 
 int unit_file_get_default(
@@ -1706,123 +1980,101 @@ int unit_file_get_default(
                 char **name) {
 
         _cleanup_lookup_paths_free_ LookupPaths paths = {};
-        char **p;
+        _cleanup_(install_context_done) InstallContext c = {};
+        UnitFileInstallInfo *i;
+        char *n;
         int r;
 
         assert(scope >= 0);
         assert(scope < _UNIT_FILE_SCOPE_MAX);
         assert(name);
 
-        r = lookup_paths_init_from_scope(&paths, scope, root_dir);
+        r = verify_root_dir(scope, &root_dir);
         if (r < 0)
                 return r;
 
-        STRV_FOREACH(p, paths.unit_path) {
-                _cleanup_free_ char *path = NULL, *tmp = NULL;
-                char *n;
-
-                path = path_join(root_dir, *p, SPECIAL_DEFAULT_TARGET);
-                if (!path)
-                        return -ENOMEM;
-
-                r = readlink_malloc(path, &tmp);
-                if (r == -ENOENT)
-                        continue;
-                else if (r == -EINVAL)
-                        /* not a symlink */
-                        n = strdup(SPECIAL_DEFAULT_TARGET);
-                else if (r < 0)
-                        return r;
-                else
-                        n = strdup(basename(tmp));
+        r = lookup_paths_init_from_scope(&paths, scope, root_dir);
+        if (r < 0)
+                return r;
 
-                if (!n)
-                        return -ENOMEM;
+        r = install_info_discover(scope, &c, root_dir, &paths, SPECIAL_DEFAULT_TARGET, SEARCH_FOLLOW_CONFIG_SYMLINKS, &i);
+        if (r < 0)
+                return r;
+        if (i->type == UNIT_FILE_TYPE_MASKED)
+                return -ESHUTDOWN;
 
-                *name = n;
-                return 0;
-        }
+        n = strdup(i->name);
+        if (!n)
+                return -ENOMEM;
 
-        return -ENOENT;
+        *name = n;
+        return 0;
 }
 
-UnitFileState unit_file_lookup_state(
+int unit_file_lookup_state(
                 UnitFileScope scope,
                 const char *root_dir,
                 const LookupPaths *paths,
-                const char *name) {
+                const char *name,
+                UnitFileState *ret) {
 
-        UnitFileState state = _UNIT_FILE_STATE_INVALID;
-        char **i;
-        _cleanup_free_ char *path = NULL;
-        int r = 0;
+        _cleanup_(install_context_done) InstallContext c = {};
+        UnitFileInstallInfo *i;
+        UnitFileState state;
+        int r;
 
         assert(paths);
+        assert(name);
 
         if (!unit_name_is_valid(name, UNIT_NAME_ANY))
                 return -EINVAL;
 
-        STRV_FOREACH(i, paths->unit_path) {
-                struct stat st;
-                char *partial;
-                bool also = false;
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
 
-                free(path);
-                path = path_join(root_dir, *i, name);
-                if (!path)
-                        return -ENOMEM;
+        r = install_info_discover(scope, &c, root_dir, paths, name, SEARCH_LOAD|SEARCH_FOLLOW_CONFIG_SYMLINKS, &i);
+        if (r < 0)
+                return r;
 
-                if (root_dir)
-                        partial = path + strlen(root_dir);
-                else
-                        partial = path;
-
-                /*
-                 * Search for a unit file in our default paths, to
-                 * be sure, that there are no broken symlinks.
-                 */
-                if (lstat(path, &st) < 0) {
-                        r = -errno;
-                        if (errno != ENOENT)
-                                return r;
+        /* Shortcut things, if the caller just wants to know if this unit exists. */
+        if (!ret)
+                return 0;
 
-                        if (!unit_name_is_valid(name, UNIT_NAME_INSTANCE))
-                                continue;
-                } else {
-                        if (!S_ISREG(st.st_mode) && !S_ISLNK(st.st_mode))
-                                return -ENOENT;
+        switch (i->type) {
 
-                        r = null_or_empty_path(path);
-                        if (r < 0 && r != -ENOENT)
-                                return r;
-                        else if (r > 0) {
-                                state = path_startswith(*i, "/run") ? UNIT_FILE_MASKED_RUNTIME : UNIT_FILE_MASKED;
-                                return state;
-                        }
-                }
+        case UNIT_FILE_TYPE_MASKED:
+                state = path_startswith(i->path, "/run") ? UNIT_FILE_MASKED_RUNTIME : UNIT_FILE_MASKED;
+                break;
 
-                r = find_symlinks_in_scope(scope, root_dir, name, &state);
+        case UNIT_FILE_TYPE_REGULAR:
+                r = find_symlinks_in_scope(scope, root_dir, i->name, &state);
                 if (r < 0)
                         return r;
-                else if (r > 0)
-                        return state;
+                if (r == 0) {
+                        if (UNIT_FILE_INSTALL_INFO_HAS_RULES(i))
+                                state = UNIT_FILE_DISABLED;
+                        else if (UNIT_FILE_INSTALL_INFO_HAS_ALSO(i))
+                                state = UNIT_FILE_INDIRECT;
+                        else
+                                state = UNIT_FILE_STATIC;
+                }
 
-                r = unit_file_can_install(paths, root_dir, partial, true, &also);
-                if (r < 0 && errno != ENOENT)
-                        return r;
-                else if (r > 0)
-                        return UNIT_FILE_DISABLED;
-                else if (r == 0)
-                        return also ? UNIT_FILE_INDIRECT : UNIT_FILE_STATIC;
+                break;
+
+        default:
+                assert_not_reached("Unexpect unit file type.");
         }
 
-        return r < 0 ? r : state;
+        *ret = state;
+        return 0;
 }
 
-UnitFileState unit_file_get_state(
+int unit_file_get_state(
                 UnitFileScope scope,
                 const char *root_dir,
-                const char *name) {
+                const char *name,
+                UnitFileState *ret) {
 
         _cleanup_lookup_paths_free_ LookupPaths paths = {};
         int r;
@@ -1831,14 +2083,15 @@ UnitFileState unit_file_get_state(
         assert(scope < _UNIT_FILE_SCOPE_MAX);
         assert(name);
 
-        if (root_dir && scope != UNIT_FILE_SYSTEM)
-                return -EINVAL;
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
 
         r = lookup_paths_init_from_scope(&paths, scope, root_dir);
         if (r < 0)
                 return r;
 
-        return unit_file_lookup_state(scope, root_dir, &paths, name);
+        return unit_file_lookup_state(scope, root_dir, &paths, name, ret);
 }
 
 int unit_file_query_preset(UnitFileScope scope, const char *root_dir, const char *name) {
@@ -1850,6 +2103,13 @@ int unit_file_query_preset(UnitFileScope scope, const char *root_dir, const char
         assert(scope < _UNIT_FILE_SCOPE_MAX);
         assert(name);
 
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
+
+        if (!unit_name_is_valid(name, UNIT_NAME_ANY))
+                return -EINVAL;
+
         if (scope == UNIT_FILE_SYSTEM)
                 r = conf_files_list(&files, ".preset", root_dir,
                                     "/etc/systemd/system-preset",
@@ -1866,13 +2126,14 @@ int unit_file_query_preset(UnitFileScope scope, const char *root_dir, const char
                                     "/usr/lib/systemd/user-preset",
                                     NULL);
         else
-                return 1;
+                return 1; /* Default is "enable" */
 
         if (r < 0)
                 return r;
 
         STRV_FOREACH(p, files) {
                 _cleanup_fclose_ FILE *f;
+                char line[LINE_MAX];
 
                 f = fopen(*p, "re");
                 if (!f) {
@@ -1882,39 +2143,38 @@ int unit_file_query_preset(UnitFileScope scope, const char *root_dir, const char
                         return -errno;
                 }
 
-                for (;;) {
-                        char line[LINE_MAX], *l;
-
-                        if (!fgets(line, sizeof(line), f))
-                                break;
+                FOREACH_LINE(line, f, return -errno) {
+                        const char *parameter;
+                        char *l;
 
                         l = strstrip(line);
-                        if (!*l)
-                                continue;
 
-                        if (strchr(COMMENTS "\n", *l))
+                        if (isempty(l))
+                                continue;
+                        if (strchr(COMMENTS, *l))
                                 continue;
 
-                        if (first_word(l, "enable")) {
-                                l += 6;
-                                l += strspn(l, WHITESPACE);
-
-                                if (fnmatch(l, name, FNM_NOESCAPE) == 0) {
+                        parameter = first_word(l, "enable");
+                        if (parameter) {
+                                if (fnmatch(parameter, name, FNM_NOESCAPE) == 0) {
                                         log_debug("Preset file says enable %s.", name);
                                         return 1;
                                 }
 
-                        } else if (first_word(l, "disable")) {
-                                l += 7;
-                                l += strspn(l, WHITESPACE);
+                                continue;
+                        }
 
-                                if (fnmatch(l, name, FNM_NOESCAPE) == 0) {
+                        parameter = first_word(l, "disable");
+                        if (parameter) {
+                                if (fnmatch(parameter, name, FNM_NOESCAPE) == 0) {
                                         log_debug("Preset file says disable %s.", name);
                                         return 0;
                                 }
 
-                        } else
-                                log_debug("Couldn't parse line '%s'", l);
+                                continue;
+                        }
+
+                        log_debug("Couldn't parse line '%s'", l);
                 }
         }
 
@@ -1923,6 +2183,86 @@ int unit_file_query_preset(UnitFileScope scope, const char *root_dir, const char
         return 1;
 }
 
+static int execute_preset(
+                UnitFileScope scope,
+                InstallContext *plus,
+                InstallContext *minus,
+                const LookupPaths *paths,
+                const char *config_path,
+                const char *root_dir,
+                char **files,
+                UnitFilePresetMode mode,
+                bool force,
+                UnitFileChange **changes,
+                unsigned *n_changes) {
+
+        int r;
+
+        assert(plus);
+        assert(minus);
+        assert(paths);
+        assert(config_path);
+
+        if (mode != UNIT_FILE_PRESET_ENABLE_ONLY) {
+                _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
+
+                r = install_context_mark_for_removal(scope, minus, paths, &remove_symlinks_to, config_path, root_dir);
+                if (r < 0)
+                        return r;
+
+                r = remove_marked_symlinks(remove_symlinks_to, config_path, changes, n_changes);
+        } else
+                r = 0;
+
+        if (mode != UNIT_FILE_PRESET_DISABLE_ONLY) {
+                int q;
+
+                /* Returns number of symlinks that where supposed to be installed. */
+                q = install_context_apply(scope, plus, paths, config_path, root_dir, force, SEARCH_LOAD, changes, n_changes);
+                if (r >= 0) {
+                        if (q < 0)
+                                r = q;
+                        else
+                                r+= q;
+                }
+        }
+
+        return r;
+}
+
+static int preset_prepare_one(
+                UnitFileScope scope,
+                InstallContext *plus,
+                InstallContext *minus,
+                LookupPaths *paths,
+                const char *root_dir,
+                UnitFilePresetMode mode,
+                const char *name) {
+
+        UnitFileInstallInfo *i;
+        int r;
+
+        if (install_info_find(plus, name) ||
+            install_info_find(minus, name))
+                return 0;
+
+        r = unit_file_query_preset(scope, root_dir, name);
+        if (r < 0)
+                return r;
+
+        if (r > 0) {
+                r = install_info_discover(scope, plus, root_dir, paths, name, SEARCH_LOAD|SEARCH_FOLLOW_CONFIG_SYMLINKS, &i);
+                if (r < 0)
+                        return r;
+
+                if (i->type == UNIT_FILE_TYPE_MASKED)
+                        return -ESHUTDOWN;
+        } else
+                r = install_info_discover(scope, minus, root_dir, paths, name, SEARCH_FOLLOW_CONFIG_SYMLINKS, &i);
+
+        return r;
+}
+
 int unit_file_preset(
                 UnitFileScope scope,
                 bool runtime,
@@ -1937,12 +2277,16 @@ int unit_file_preset(
         _cleanup_lookup_paths_free_ LookupPaths paths = {};
         _cleanup_free_ char *config_path = NULL;
         char **i;
-        int r, q;
+        int r;
 
         assert(scope >= 0);
         assert(scope < _UNIT_FILE_SCOPE_MAX);
         assert(mode < _UNIT_FILE_PRESET_MAX);
 
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
+
         r = lookup_paths_init_from_scope(&paths, scope, root_dir);
         if (r < 0)
                 return r;
@@ -1952,44 +2296,15 @@ int unit_file_preset(
                 return r;
 
         STRV_FOREACH(i, files) {
-
                 if (!unit_name_is_valid(*i, UNIT_NAME_ANY))
                         return -EINVAL;
 
-                r = unit_file_query_preset(scope, root_dir, *i);
+                r = preset_prepare_one(scope, &plus, &minus, &paths, root_dir, mode, *i);
                 if (r < 0)
                         return r;
-
-                if (r && mode != UNIT_FILE_PRESET_DISABLE_ONLY)
-                        r = install_info_add_auto(&plus, *i);
-                else if (!r && mode != UNIT_FILE_PRESET_ENABLE_ONLY)
-                        r = install_info_add_auto(&minus, *i);
-                else
-                        r = 0;
-                if (r < 0)
-                        return r;
-        }
-
-        r = 0;
-
-        if (mode != UNIT_FILE_PRESET_ENABLE_ONLY) {
-                _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
-
-                r = install_context_mark_for_removal(&minus, &paths, &remove_symlinks_to, config_path, root_dir);
-
-                q = remove_marked_symlinks(remove_symlinks_to, config_path, changes, n_changes, files);
-                if (r >= 0)
-                        r = q;
-        }
-
-        if (mode != UNIT_FILE_PRESET_DISABLE_ONLY) {
-                /* Returns number of symlinks that where supposed to be installed. */
-                q = install_context_apply(&plus, &paths, config_path, root_dir, force, changes, n_changes);
-                if (r >= 0)
-                        r = q;
         }
 
-        return r;
+        return execute_preset(scope, &plus, &minus, &paths, config_path, root_dir, files, mode, force, changes, n_changes);
 }
 
 int unit_file_preset_all(
@@ -2005,12 +2320,16 @@ int unit_file_preset_all(
         _cleanup_lookup_paths_free_ LookupPaths paths = {};
         _cleanup_free_ char *config_path = NULL;
         char **i;
-        int r, q;
+        int r;
 
         assert(scope >= 0);
         assert(scope < _UNIT_FILE_SCOPE_MAX);
         assert(mode < _UNIT_FILE_PRESET_MAX);
 
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
+
         r = lookup_paths_init_from_scope(&paths, scope, root_dir);
         if (r < 0)
                 return r;
@@ -2043,43 +2362,16 @@ int unit_file_preset_all(
 
                         dirent_ensure_type(d, de);
 
-                        if (de->d_type != DT_REG)
+                        if (!IN_SET(de->d_type, DT_LNK, DT_REG))
                                 continue;
 
-                        r = unit_file_query_preset(scope, root_dir, de->d_name);
-                        if (r < 0)
-                                return r;
-
-                        if (r && mode != UNIT_FILE_PRESET_DISABLE_ONLY)
-                                r = install_info_add_auto(&plus, de->d_name);
-                        else if (!r && mode != UNIT_FILE_PRESET_ENABLE_ONLY)
-                                r = install_info_add_auto(&minus, de->d_name);
-                        else
-                                r = 0;
+                        r = preset_prepare_one(scope, &plus, &minus, &paths, root_dir, mode, de->d_name);
                         if (r < 0)
                                 return r;
                 }
         }
 
-        r = 0;
-
-        if (mode != UNIT_FILE_PRESET_ENABLE_ONLY) {
-                _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
-
-                r = install_context_mark_for_removal(&minus, &paths, &remove_symlinks_to, config_path, root_dir);
-
-                q = remove_marked_symlinks(remove_symlinks_to, config_path, changes, n_changes, NULL);
-                if (r >= 0)
-                        r = q;
-        }
-
-        if (mode != UNIT_FILE_PRESET_DISABLE_ONLY) {
-                q = install_context_apply(&plus, &paths, config_path, root_dir, force, changes, n_changes);
-                if (r >= 0)
-                        r = q;
-        }
-
-        return r;
+        return execute_preset(scope, &plus, &minus, &paths, config_path, root_dir, NULL, mode, force, changes, n_changes);
 }
 
 static void unit_file_list_free_one(UnitFileList *f) {
@@ -2090,6 +2382,15 @@ static void unit_file_list_free_one(UnitFileList *f) {
         free(f);
 }
 
+Hashmap* unit_file_list_free(Hashmap *h) {
+        UnitFileList *i;
+
+        while ((i = hashmap_steal_first(h)))
+                unit_file_list_free_one(i);
+
+        return hashmap_free(h);
+}
+
 DEFINE_TRIVIAL_CLEANUP_FUNC(UnitFileList*, unit_file_list_free_one);
 
 int unit_file_get_list(
@@ -2105,14 +2406,9 @@ int unit_file_get_list(
         assert(scope < _UNIT_FILE_SCOPE_MAX);
         assert(h);
 
-        if (root_dir && scope != UNIT_FILE_SYSTEM)
-                return -EINVAL;
-
-        if (root_dir) {
-                r = access(root_dir, F_OK);
-                if (r < 0)
-                        return -errno;
-        }
+        r = verify_root_dir(scope, &root_dir);
+        if (r < 0)
+                return r;
 
         r = lookup_paths_init_from_scope(&paths, scope, root_dir);
         if (r < 0)
@@ -2137,8 +2433,6 @@ int unit_file_get_list(
 
                 FOREACH_DIRENT(de, d, return -errno) {
                         _cleanup_(unit_file_list_free_onep) UnitFileList *f = NULL;
-                        _cleanup_free_ char *path = NULL;
-                        bool also = false;
 
                         if (!unit_name_is_valid(de->d_name, UNIT_NAME_ANY))
                                 continue;
@@ -2159,44 +2453,14 @@ int unit_file_get_list(
                         if (!f->path)
                                 return -ENOMEM;
 
-                        r = null_or_empty_path(f->path);
-                        if (r < 0 && r != -ENOENT)
-                                return r;
-                        if (r > 0) {
-                                f->state =
-                                        path_startswith(*i, "/run") ?
-                                        UNIT_FILE_MASKED_RUNTIME : UNIT_FILE_MASKED;
-                                goto found;
-                        }
-
-                        r = find_symlinks_in_scope(scope, root_dir, de->d_name, &f->state);
+                        r = unit_file_lookup_state(scope, root_dir, &paths, basename(f->path), &f->state);
                         if (r < 0)
-                                return r;
-                        if (r > 0) {
-                                f->state = UNIT_FILE_ENABLED;
-                                goto found;
-                        }
-
-                        path = path_make_absolute(de->d_name, *i);
-                        if (!path)
-                                return -ENOMEM;
+                                f->state = UNIT_FILE_BAD;
 
-                        r = unit_file_can_install(&paths, root_dir, path, true, &also);
-                        if (r == -EINVAL ||  /* Invalid setting? */
-                            r == -EBADMSG || /* Invalid format? */
-                            r == -ENOENT     /* Included file not found? */)
-                                f->state = UNIT_FILE_INVALID;
-                        else if (r < 0)
-                                return r;
-                        else if (r > 0)
-                                f->state = UNIT_FILE_DISABLED;
-                        else
-                                f->state = also ? UNIT_FILE_INDIRECT : UNIT_FILE_STATIC;
-
-                found:
                         r = hashmap_put(h, basename(f->path), f);
                         if (r < 0)
                                 return r;
+
                         f = NULL; /* prevent cleanup */
                 }
         }
@@ -2214,7 +2478,7 @@ static const char* const unit_file_state_table[_UNIT_FILE_STATE_MAX] = {
         [UNIT_FILE_STATIC] = "static",
         [UNIT_FILE_DISABLED] = "disabled",
         [UNIT_FILE_INDIRECT] = "indirect",
-        [UNIT_FILE_INVALID] = "invalid",
+        [UNIT_FILE_BAD] = "bad",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(unit_file_state, UnitFileState);
diff --git a/src/shared/install.h b/src/shared/install.h
index 74d9ebab65..b1ab66f0d4 100644
--- a/src/shared/install.h
+++ b/src/shared/install.h
@@ -25,13 +25,15 @@ typedef enum UnitFileScope UnitFileScope;
 typedef enum UnitFileState UnitFileState;
 typedef enum UnitFilePresetMode UnitFilePresetMode;
 typedef enum UnitFileChangeType UnitFileChangeType;
+typedef enum UnitFileType UnitFileType;
 typedef struct UnitFileChange UnitFileChange;
 typedef struct UnitFileList UnitFileList;
 typedef struct UnitFileInstallInfo UnitFileInstallInfo;
 
 #include "hashmap.h"
-#include "unit-name.h"
 #include "path-lookup.h"
+#include "strv.h"
+#include "unit-name.h"
 
 enum UnitFileScope {
         UNIT_FILE_SYSTEM,
@@ -51,7 +53,7 @@ enum UnitFileState {
         UNIT_FILE_STATIC,
         UNIT_FILE_DISABLED,
         UNIT_FILE_INDIRECT,
-        UNIT_FILE_INVALID,
+        UNIT_FILE_BAD,
         _UNIT_FILE_STATE_MAX,
         _UNIT_FILE_STATE_INVALID = -1
 };
@@ -82,6 +84,14 @@ struct UnitFileList {
         UnitFileState state;
 };
 
+enum UnitFileType {
+        UNIT_FILE_TYPE_REGULAR,
+        UNIT_FILE_TYPE_SYMLINK,
+        UNIT_FILE_TYPE_MASKED,
+        _UNIT_FILE_TYPE_MAX,
+        _UNIT_FILE_TYPE_INVALID = -1,
+};
+
 struct UnitFileInstallInfo {
         char *name;
         char *path;
@@ -93,8 +103,26 @@ struct UnitFileInstallInfo {
         char **also;
 
         char *default_instance;
+
+        UnitFileType type;
+
+        char *symlink_target;
 };
 
+static inline bool UNIT_FILE_INSTALL_INFO_HAS_RULES(UnitFileInstallInfo *i) {
+        assert(i);
+
+        return !strv_isempty(i->aliases) ||
+               !strv_isempty(i->wanted_by) ||
+               !strv_isempty(i->required_by);
+}
+
+static inline bool UNIT_FILE_INSTALL_INFO_HAS_ALSO(UnitFileInstallInfo *i) {
+        assert(i);
+
+        return !strv_isempty(i->also);
+}
+
 int unit_file_enable(UnitFileScope scope, bool runtime, const char *root_dir, char **files, bool force, UnitFileChange **changes, unsigned *n_changes);
 int unit_file_disable(UnitFileScope scope, bool runtime, const char *root_dir, char **files, UnitFileChange **changes, unsigned *n_changes);
 int unit_file_reenable(UnitFileScope scope, bool runtime, const char *root_dir, char **files, bool force, UnitFileChange **changes, unsigned *n_changes);
@@ -105,14 +133,14 @@ int unit_file_mask(UnitFileScope scope, bool runtime, const char *root_dir, char
 int unit_file_unmask(UnitFileScope scope, bool runtime, const char *root_dir, char **files, UnitFileChange **changes, unsigned *n_changes);
 int unit_file_set_default(UnitFileScope scope, const char *root_dir, const char *file, bool force, UnitFileChange **changes, unsigned *n_changes);
 int unit_file_get_default(UnitFileScope scope, const char *root_dir, char **name);
-int unit_file_add_dependency(UnitFileScope scope, bool runtime, const char *root_dir, char **files, char *target, UnitDependency dep, bool force, UnitFileChange **changes, unsigned *n_changes);
+int unit_file_add_dependency(UnitFileScope scope, bool runtime, const char *root_dir, char **files, const char *target, UnitDependency dep, bool force, UnitFileChange **changes, unsigned *n_changes);
 
-UnitFileState unit_file_lookup_state(UnitFileScope scope, const char *root_dir,const LookupPaths *paths, const char *name);
-UnitFileState unit_file_get_state(UnitFileScope scope, const char *root_dir, const char *filename);
+int unit_file_lookup_state(UnitFileScope scope, const char *root_dir,const LookupPaths *paths, const char *name, UnitFileState *ret);
+int unit_file_get_state(UnitFileScope scope, const char *root_dir, const char *filename, UnitFileState *ret);
 
 int unit_file_get_list(UnitFileScope scope, const char *root_dir, Hashmap *h);
+Hashmap* unit_file_list_free(Hashmap *h);
 
-void unit_file_list_free(Hashmap *h);
 int unit_file_changes_add(UnitFileChange **changes, unsigned *n_changes, UnitFileChangeType type, const char *path, const char *source);
 void unit_file_changes_free(UnitFileChange *changes, unsigned n_changes);