diff options
| -rw-r--r-- | src/core/switch-root.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/src/core/switch-root.c b/src/core/switch-root.c index 150332a858..ce0e41d510 100644 --- a/src/core/switch-root.c +++ b/src/core/switch-root.c @@ -30,6 +30,7 @@ #include "util.h" #include "path-util.h" #include "switch-root.h" +#include "missing.h" int switch_root(const char *new_root) { @@ -44,10 +45,21 @@ int switch_root(const char *new_root) { struct stat new_root_stat; bool old_root_remove; const char *i; + _cleanup_free_ char *temporary_old_root = NULL; if (path_equal(new_root, "/")) return 0; + /* When using pivot_root() we assume that /mnt exists as place + * we can temporarily move the old root to. As we immediately + * unmount it from there it doesn't matter much which + * directory we choose for this, but it should be more likely + * than not that /mnt exists and is suitable as mount point + * and is on the same fs as the old root dir */ + temporary_old_root = strappend(new_root, "/mnt"); + if (!temporary_old_root) + return -ENOMEM; + old_root_remove = in_initrd(); if (stat(new_root, &new_root_stat) < 0) { @@ -103,7 +115,20 @@ int switch_root(const char *new_root) { log_warning("Failed to open root directory: %m"); } - if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) { + /* We first try a pivot_root() so that we can umount the old + * root dir. In many cases (i.e. where rootfs is /), that's + * not possible however, and hence we simply overmount root */ + if (pivot_root(new_root, temporary_old_root) >= 0) { + + /* Immediately get rid of the old root. Since we are + * running off it we need to do this lazily. */ + if (umount2(temporary_old_root, MNT_DETACH) < 0) { + r = -errno; + log_error("Failed to umount old root dir %s: %m", temporary_old_root); + goto fail; + } + + } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) { r = -errno; log_error("Failed to mount moving %s to /: %m", new_root); goto fail; |