fstab-generator: initrd - mount selected entries from /sysroot/etc/fstab

We only mount "/usr" and entries marked with "x-initrd.mount".

This (together with the right unit files) is needed in the initramfs in order to
natively support mounting /usr (and friends) from the initramfs.

The way it is meant to work is:
 * wait for sysroot.mount to be mounted
 * do a daemon-reload to generate sysroot-usr.mount (++) from /sysroot/etc/fstab
 * wait for sysroot-usr.mount to be mounted
 * switch-root

Cc: Harald Hoyer <harald.hoyer@gmail.com>
Cc: Dave Reisner <d@falconindy.com>

1 files changed, 28 insertions, 11 deletions

diff --git a/src/fstab-generator/fstab-generator.c b/src/fstab-generator/fstab-generator.c
index 23a8d79813..1a1fe8605f 100644
--- a/src/fstab-generator/fstab-generator.c
+++ b/src/fstab-generator/fstab-generator.c
@@ -191,6 +191,14 @@ static bool mount_is_network(struct mntent *me) {
                 fstype_is_network(me->mnt_type);
 }
 
+static bool mount_in_initrd(struct mntent *me) {
+        assert(me);
+
+        return
+                hasmntopt(me, "x-initrd.mount") ||
+                streq(me->mnt_dir, "/usr");
+}
+
 static int add_mount(const char *what, const char *where, const char *type, const char *opts,
                      int passno, bool noauto, bool nofail, bool automount, bool isbind, bool isnetwork,
                      const char *source) {
@@ -342,13 +350,14 @@ static int add_mount(const char *what, const char *where, const char *type, cons
                 fprintf(f,
                         "# Automatically generated by systemd-fstab-generator\n\n"
                         "[Unit]\n"
-                        "SourcePath=/etc/fstab\n"
+                        "SourcePath=%s\n"
                         "DefaultDependencies=no\n"
                         "Conflicts=" SPECIAL_UMOUNT_TARGET "\n"
                         "Before=" SPECIAL_UMOUNT_TARGET " %s\n"
                         "\n"
                         "[Automount]\n"
                         "Where=%s\n",
+                        source,
                         post,
                         where);
 
@@ -373,18 +382,20 @@ static int add_mount(const char *what, const char *where, const char *type, cons
         return 0;
 }
 
-static int parse_fstab(void) {
+static int parse_fstab(const char *prefix, bool initrd) {
         FILE *f;
+        _cleanup_free_ char *fstab_path = NULL;
         int r = 0;
         struct mntent *me;
 
         errno = 0;
-        f = setmntent("/etc/fstab", "r");
+        fstab_path = strjoin(prefix, "/etc/fstab", NULL);
+        f = setmntent(fstab_path, "r");
         if (!f) {
                 if (errno == ENOENT)
                         return 0;
 
-                log_error("Failed to open /etc/fstab: %m");
+                log_error("Failed to open %s/etc/fstab: %m", prefix);
                 return -errno;
         }
 
@@ -392,8 +403,11 @@ static int parse_fstab(void) {
                 char _cleanup_free_ *where = NULL, *what = NULL;
                 int k;
 
+                if (initrd && !mount_in_initrd(me))
+                        continue;
+
                 what = fstab_node_to_udev_node(me->mnt_fsname);
-                where = strdup(me->mnt_dir);
+                where = strjoin(prefix, me->mnt_dir, NULL);
                 if (!what || !where) {
                         r = log_oom();
                         goto finish;
@@ -419,7 +433,7 @@ static int parse_fstab(void) {
 
                         k = add_mount(what, where, me->mnt_type, me->mnt_opts,
                                      me->mnt_passno, noauto, nofail, automount,
-                                     isbind, isnetwork, "/etc/fstab");
+                                     isbind, isnetwork, fstab_path);
                 }
 
                 if (k < 0)
@@ -552,7 +566,7 @@ static int parse_proc_cmdline(void) {
 }
 
 int main(int argc, char *argv[]) {
-        int r, k = 0;
+        int r = 0, k, l = 0;
 
         if (argc > 1 && argc != 4) {
                 log_error("This program takes three or no arguments.");
@@ -572,12 +586,15 @@ int main(int argc, char *argv[]) {
                 return EXIT_FAILURE;
 
         if (in_initrd())
-                k = parse_new_root_from_proc_cmdline();
+                r = parse_new_root_from_proc_cmdline();
 
         if (!arg_enabled)
-                return EXIT_SUCCESS;
+                return (r < 0) ? EXIT_FAILURE : EXIT_SUCCESS;
 
-        r = parse_fstab();
+        k = parse_fstab("", false);
+
+        if (in_initrd())
+                l = parse_fstab("/sysroot", true);
 
-        return (r < 0) || (k < 0) ? EXIT_FAILURE : EXIT_SUCCESS;
+        return (r < 0) || (k < 0) || (l < 0) ? EXIT_FAILURE : EXIT_SUCCESS;
 }