shared, systemctl: teach is-enabled to show installation targets

It may be desired by users to know what targets a particular service is
installed into. Improve user friendliness by teaching the is-enabled
command to show such information when used with --full.

This patch makes use of the newly added UnitFileFlags and adds
UNIT_FILE_DRY_RUN flag into it. Since the API had already been modified,
it's now easy to add the new dry-run feature for other commands as
well. As a next step, --dry-run could be added to systemctl, which in
turn might pave the way for a long requested dry-run feature when
running systemctl start.

6 files changed, 145 insertions, 19 deletions

diff --git a/man/systemctl.xml b/man/systemctl.xml
index 75885bcf02..a4d4c53725 100644
--- a/man/systemctl.xml
+++ b/man/systemctl.xml
@@ -233,6 +233,8 @@
           of <command>status</command>, <command>list-units</command>,
           <command>list-jobs</command>, and
           <command>list-timers</command>.</para>
+          <para>Also, show installation targets in the output of
+          <command>is-enabled</command>.</para>
         </listitem>
       </varlistentry>
 
@@ -1136,6 +1138,7 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
             exit code of 0 if at least one is enabled, non-zero
             otherwise. Prints the current enable status (see table).
             To suppress this output, use <option>--quiet</option>.
+            To show installation targets, use <option>--full</option>.
             </para>
 
             <table>
diff --git a/src/core/dbus-manager.c b/src/core/dbus-manager.c
index ecad71a5aa..d7d3d3c8ce 100644
--- a/src/core/dbus-manager.c
+++ b/src/core/dbus-manager.c
@@ -2242,6 +2242,49 @@ static int method_add_dependency_unit_files(sd_bus_message *message, void *userd
         return reply_unit_file_changes_and_free(m, message, -1, changes, n_changes);
 }
 
+static int method_get_unit_file_links(sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
+        UnitFileChange *changes = NULL;
+        unsigned n_changes = 0, i;
+        UnitFileFlags flags;
+        const char *name;
+        char **p;
+        int runtime, r;
+
+        r = sd_bus_message_read(message, "sb", &name, &runtime);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_new_method_return(message, &reply);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_open_container(reply, SD_BUS_TYPE_ARRAY, "s");
+        if (r < 0)
+                return r;
+
+        p = STRV_MAKE(name);
+        flags = UNIT_FILE_DRY_RUN |
+                (runtime ? UNIT_FILE_RUNTIME : 0);
+
+        r = unit_file_disable(UNIT_FILE_SYSTEM, flags, NULL, p, &changes, &n_changes);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get file links for %s: %m", name);
+
+        for (i = 0; i < n_changes; i++)
+                if (changes[i].type == UNIT_FILE_UNLINK) {
+                        r = sd_bus_message_append(reply, "s", changes[i].path);
+                        if (r < 0)
+                                return r;
+                }
+
+        r = sd_bus_message_close_container(reply);
+        if (r < 0)
+                return r;
+
+        return sd_bus_send(NULL, reply, NULL);
+}
+
 const sd_bus_vtable bus_manager_vtable[] = {
         SD_BUS_VTABLE_START(0),
 
@@ -2387,6 +2430,7 @@ const sd_bus_vtable bus_manager_vtable[] = {
         SD_BUS_METHOD("GetDefaultTarget", NULL, "s", method_get_default_target, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("PresetAllUnitFiles", "sbb", "a(sss)", method_preset_all_unit_files, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("AddDependencyUnitFiles", "asssbb", "a(sss)", method_add_dependency_unit_files, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("GetUnitFileLinks", "sb", "as", method_get_unit_file_links, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("SetExitCode", "y", NULL, method_set_exit_code, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("LookupDynamicUserByName", "s", "u", method_lookup_dynamic_user_by_name, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("LookupDynamicUserByUID", "u", "s", method_lookup_dynamic_user_by_uid, SD_BUS_VTABLE_UNPRIVILEGED),
diff --git a/src/core/org.freedesktop.systemd1.conf b/src/core/org.freedesktop.systemd1.conf
index 6caa15b0b8..a61677e645 100644
--- a/src/core/org.freedesktop.systemd1.conf
+++ b/src/core/org.freedesktop.systemd1.conf
@@ -94,6 +94,10 @@
 
                 <allow send_destination="org.freedesktop.systemd1"
                        send_interface="org.freedesktop.systemd1.Manager"
+                       send_member="GetUnitFileLinks"/>
+
+                <allow send_destination="org.freedesktop.systemd1"
+                       send_interface="org.freedesktop.systemd1.Manager"
                        send_member="ListJobs"/>
 
                 <allow send_destination="org.freedesktop.systemd1"
diff --git a/src/shared/install.c b/src/shared/install.c
index caca23435a..96fba6e25b 100644
--- a/src/shared/install.c
+++ b/src/shared/install.c
@@ -518,6 +518,7 @@ static int remove_marked_symlinks_fd(
                 const char *path,
                 const char *config_path,
                 const LookupPaths *lp,
+                bool dry_run,
                 bool *restart,
                 UnitFileChange **changes,
                 unsigned *n_changes) {
@@ -566,7 +567,7 @@ 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, lp, restart, changes, n_changes);
+                        q = remove_marked_symlinks_fd(remove_symlinks_to, nfd, p, config_path, lp, dry_run, restart, changes, n_changes);
                         if (q < 0 && r == 0)
                                 r = q;
 
@@ -603,14 +604,16 @@ static int remove_marked_symlinks_fd(
                         if (!found)
                                 continue;
 
-                        if (unlinkat(fd, de->d_name, 0) < 0 && errno != ENOENT) {
-                                if (r == 0)
-                                        r = -errno;
-                                unit_file_changes_add(changes, n_changes, -errno, p, NULL);
-                                continue;
-                        }
+                        if (!dry_run) {
+                                if (unlinkat(fd, de->d_name, 0) < 0 && errno != ENOENT) {
+                                        if (r == 0)
+                                                r = -errno;
+                                        unit_file_changes_add(changes, n_changes, -errno, p, NULL);
+                                        continue;
+                                }
 
-                        (void) rmdir_parents(p, config_path);
+                                (void) rmdir_parents(p, config_path);
+                        }
 
                         unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, p, NULL);
 
@@ -621,7 +624,7 @@ static int remove_marked_symlinks_fd(
                         q = mark_symlink_for_removal(&remove_symlinks_to, rp ?: p);
                         if (q < 0)
                                 return q;
-                        if (q > 0)
+                        if (q > 0 && !dry_run)
                                 *restart = true;
                 }
         }
@@ -633,6 +636,7 @@ static int remove_marked_symlinks(
                 Set *remove_symlinks_to,
                 const char *config_path,
                 const LookupPaths *lp,
+                bool dry_run,
                 UnitFileChange **changes,
                 unsigned *n_changes) {
 
@@ -659,7 +663,7 @@ static int remove_marked_symlinks(
                         return -errno;
 
                 /* This takes possession of cfd and closes it */
-                q = remove_marked_symlinks_fd(remove_symlinks_to, cfd, config_path, config_path, lp, &restart, changes, n_changes);
+                q = remove_marked_symlinks_fd(remove_symlinks_to, cfd, config_path, config_path, lp, dry_run, &restart, changes, n_changes);
                 if (r == 0)
                         r = q;
         } while (restart);
@@ -1861,6 +1865,7 @@ int unit_file_unmask(
         size_t n_todo = 0, n_allocated = 0;
         const char *config_path;
         char **i;
+        bool dry_run;
         int r, q;
 
         assert(scope >= 0);
@@ -1871,6 +1876,7 @@ int unit_file_unmask(
                 return r;
 
         config_path = (flags & UNIT_FILE_RUNTIME) ? paths.runtime_config : paths.persistent_config;
+        dry_run = !!(flags & UNIT_FILE_DRY_RUN);
 
         STRV_FOREACH(i, files) {
                 _cleanup_free_ char *path = NULL;
@@ -1907,7 +1913,7 @@ int unit_file_unmask(
                 if (!path)
                         return -ENOMEM;
 
-                if (unlink(path) < 0) {
+                if (!dry_run && unlink(path) < 0) {
                         if (errno != ENOENT) {
                                 if (r >= 0)
                                         r = -errno;
@@ -1925,7 +1931,7 @@ int unit_file_unmask(
                         return q;
         }
 
-        q = remove_marked_symlinks(remove_symlinks_to, config_path, &paths, changes, n_changes);
+        q = remove_marked_symlinks(remove_symlinks_to, config_path, &paths, dry_run, changes, n_changes);
         if (r >= 0)
                 r = q;
 
@@ -2175,11 +2181,11 @@ int unit_file_revert(
                         return q;
         }
 
-        q = remove_marked_symlinks(remove_symlinks_to, paths.runtime_config, &paths, changes, n_changes);
+        q = remove_marked_symlinks(remove_symlinks_to, paths.runtime_config, &paths, false, changes, n_changes);
         if (r >= 0)
                 r = q;
 
-        q = remove_marked_symlinks(remove_symlinks_to, paths.persistent_config, &paths, changes, n_changes);
+        q = remove_marked_symlinks(remove_symlinks_to, paths.persistent_config, &paths, false, changes, n_changes);
         if (r >= 0)
                 r = q;
 
@@ -2341,7 +2347,7 @@ int unit_file_disable(
         if (r < 0)
                 return r;
 
-        return remove_marked_symlinks(remove_symlinks_to, config_path, &paths, changes, n_changes);
+        return remove_marked_symlinks(remove_symlinks_to, config_path, &paths, !!(flags & UNIT_FILE_DRY_RUN), changes, n_changes);
 }
 
 int unit_file_reenable(
@@ -2730,7 +2736,7 @@ static int execute_preset(
                 if (r < 0)
                         return r;
 
-                r = remove_marked_symlinks(remove_symlinks_to, config_path, paths, changes, n_changes);
+                r = remove_marked_symlinks(remove_symlinks_to, config_path, paths, false, changes, n_changes);
         } else
                 r = 0;
 
diff --git a/src/shared/install.h b/src/shared/install.h
index 561b521bbc..7a5859e729 100644
--- a/src/shared/install.h
+++ b/src/shared/install.h
@@ -82,6 +82,7 @@ enum UnitFileChangeType {
 enum UnitFileFlags {
         UNIT_FILE_RUNTIME = 1,
         UNIT_FILE_FORCE = 1 << 1,
+        UNIT_FILE_DRY_RUN = 1 << 2,
 };
 
 /* type can either one of the UnitFileChangeTypes listed above, or a negative error.
diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index c9ca3db3f1..2e3b59af3e 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -6271,6 +6271,63 @@ finish:
         return r;
 }
 
+static int show_installation_targets_client_side(const char *name) {
+        UnitFileChange *changes = NULL;
+        unsigned n_changes = 0, i;
+        UnitFileFlags flags;
+        char **p;
+        int r;
+
+        p = STRV_MAKE(name);
+        flags = UNIT_FILE_DRY_RUN |
+                (arg_runtime ? UNIT_FILE_RUNTIME : 0);
+
+        r = unit_file_disable(UNIT_FILE_SYSTEM, flags, NULL, p, &changes, &n_changes);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get file links for %s: %m", name);
+
+        for (i = 0; i < n_changes; i++)
+                if (changes[i].type == UNIT_FILE_UNLINK)
+                        printf("  %s\n", changes[i].path);
+
+        return 0;
+}
+
+static int show_installation_targets(sd_bus *bus, const char *name) {
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
+        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        const char *link;
+        int r;
+
+        r = sd_bus_call_method(
+                        bus,
+                        "org.freedesktop.systemd1",
+                        "/org/freedesktop/systemd1",
+                        "org.freedesktop.systemd1.Manager",
+                        "GetUnitFileLinks",
+                        &error,
+                        &reply,
+                        "sb", name, arg_runtime);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get unit file links for %s: %s", name, bus_error_message(&error, r));
+
+        r = sd_bus_message_enter_container(reply, SD_BUS_TYPE_ARRAY, "s");
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        while ((r = sd_bus_message_read(reply, "s", &link)) > 0)
+                printf("  %s\n", link);
+
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        r = sd_bus_message_exit_container(reply);
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        return 0;
+}
+
 static int unit_is_enabled(int argc, char *argv[], void *userdata) {
 
         _cleanup_strv_free_ char **names = NULL;
@@ -6289,7 +6346,6 @@ static int unit_is_enabled(int argc, char *argv[], void *userdata) {
         enabled = r > 0;
 
         if (install_client_side()) {
-
                 STRV_FOREACH(name, names) {
                         UnitFileState state;
 
@@ -6305,8 +6361,14 @@ static int unit_is_enabled(int argc, char *argv[], void *userdata) {
                                    UNIT_FILE_GENERATED))
                                 enabled = true;
 
-                        if (!arg_quiet)
+                        if (!arg_quiet) {
                                 puts(unit_file_state_to_string(state));
+                                if (arg_full) {
+                                        r = show_installation_targets_client_side(*name);
+                                        if (r < 0)
+                                                return r;
+                                }
+                        }
                 }
 
                 r = 0;
@@ -6341,8 +6403,14 @@ static int unit_is_enabled(int argc, char *argv[], void *userdata) {
                         if (STR_IN_SET(s, "enabled", "enabled-runtime", "static", "indirect", "generated"))
                                 enabled = true;
 
-                        if (!arg_quiet)
+                        if (!arg_quiet) {
                                 puts(s);
+                                if (arg_full) {
+                                        r = show_installation_targets(bus, *name);
+                                        if (r < 0)
+                                                return r;
+                                }
+                        }
                 }
         }