tmpfiles: add --root option to operate on an alternate fs tree

This makes it possible to initialize or cleanup an arbitrary filesystem
hierarchy in the same way that it would be during system boot.

2 files changed, 34 insertions, 5 deletions

diff --git a/man/systemd-tmpfiles.xml b/man/systemd-tmpfiles.xml
index 0b6264033d..fad2cbbb1a 100644
--- a/man/systemd-tmpfiles.xml
+++ b/man/systemd-tmpfiles.xml
@@ -139,19 +139,27 @@
                                 </para></listitem>
                         </varlistentry>
                         <varlistentry>
-                                <term><option>--prefix=PATH</option></term>
+                                <term><option>--prefix=<replaceable>path</replaceable></option></term>
                                 <listitem><para>Only apply rules that
                                 apply to paths with the specified
                                 prefix. This option can be specified
                                 multiple times.</para></listitem>
                         </varlistentry>
                         <varlistentry>
-                                <term><option>--exclude-prefix=PATH</option></term>
+                                <term><option>--exclude-prefix=<replaceable>path</replaceable></option></term>
                                 <listitem><para>Ignore rules that
                                 apply to paths with the specified
                                 prefix. This option can be specified
                                 multiple times.</para></listitem>
                         </varlistentry>
+                        <varlistentry>
+                                <term><option>--root=<replaceable>root</replaceable></option></term>
+                                <listitem><para>Takes a directory path
+                                as an argument. All paths will be
+                                prefixed with the given alternate <replaceable>root</replaceable>
+                                path, including config search paths.
+                                </para></listitem>
+                        </varlistentry>
 
                         <xi:include href="standard-options.xml" xpointer="help" />
                         <xi:include href="standard-options.xml" xpointer="version" />
diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index 36842898ab..52f80379e3 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -111,6 +111,7 @@ static bool arg_boot = false;
 
 static char **include_prefixes = NULL;
 static char **exclude_prefixes = NULL;
+static char *arg_root = NULL;
 
 static const char conf_file_dirs[] =
         "/etc/tmpfiles.d\0"
@@ -1188,6 +1189,15 @@ static int parse_line(const char *fname, unsigned line, const char *buffer) {
         if (!should_include_path(i->path))
                 return 0;
 
+        if (arg_root) {
+                char *p = strappend(arg_root, i->path);
+                if (!p)
+                        return log_oom();
+
+                free(i->path);
+                i->path = p;
+        }
+
         if (user && !streq(user, "-")) {
                 const char *u = user;
 
@@ -1277,7 +1287,8 @@ static int help(void) {
                "     --remove               Remove marked files/directories\n"
                "     --boot                 Execute actions only safe at boot\n"
                "     --prefix=PATH          Only apply rules that apply to paths with the specified prefix\n"
-               "     --exclude-prefix=PATH  Ignore rules that apply to paths with the specified prefix\n",
+               "     --exclude-prefix=PATH  Ignore rules that apply to paths with the specified prefix\n"
+               "     --root=PATH            Operate on an alternate filesystem root\n",
                program_invocation_short_name);
 
         return 0;
@@ -1293,6 +1304,7 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_BOOT,
                 ARG_PREFIX,
                 ARG_EXCLUDE_PREFIX,
+                ARG_ROOT,
         };
 
         static const struct option options[] = {
@@ -1304,6 +1316,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "boot",           no_argument,         NULL, ARG_BOOT           },
                 { "prefix",         required_argument,   NULL, ARG_PREFIX         },
                 { "exclude-prefix", required_argument,   NULL, ARG_EXCLUDE_PREFIX },
+                { "root",           required_argument,   NULL, ARG_ROOT           },
                 {}
         };
 
@@ -1350,6 +1363,13 @@ static int parse_argv(int argc, char *argv[]) {
                                 return log_oom();
                         break;
 
+                case ARG_ROOT:
+                        arg_root = path_make_absolute_cwd(optarg);
+                        if (!arg_root)
+                                return log_oom();
+                        path_kill_slashes(arg_root);
+                        break;
+
                 case '?':
                         return -EINVAL;
 
@@ -1376,7 +1396,7 @@ static int read_config_file(const char *fn, bool ignore_enoent) {
 
         assert(fn);
 
-        r = search_and_fopen_nulstr(fn, "re", NULL, conf_file_dirs, &f);
+        r = search_and_fopen_nulstr(fn, "re", arg_root, conf_file_dirs, &f);
         if (r < 0) {
                 if (ignore_enoent && r == -ENOENT)
                         return 0;
@@ -1477,7 +1497,7 @@ int main(int argc, char *argv[]) {
                 _cleanup_strv_free_ char **files = NULL;
                 char **f;
 
-                r = conf_files_list_nulstr(&files, ".conf", NULL, conf_file_dirs);
+                r = conf_files_list_nulstr(&files, ".conf", arg_root, conf_file_dirs);
                 if (r < 0) {
                         log_error("Failed to enumerate tmpfiles.d files: %s", strerror(-r));
                         goto finish;
@@ -1508,6 +1528,7 @@ finish:
 
         free(include_prefixes);
         free(exclude_prefixes);
+        free(arg_root);
 
         set_free_free(unix_sockets);