+/* SPDX-License-Identifier: LGPL-2.1+ */
/***
This file is part of systemd.
#include "base-filesystem.h"
#include "fd-util.h"
+#include "fs-util.h"
#include "log.h"
#include "missing.h"
#include "mkdir.h"
+#include "mount-util.h"
#include "path-util.h"
#include "rm-rf.h"
#include "stdio-util.h"
#include "string-util.h"
+#include "strv.h"
#include "switch-root.h"
#include "user-util.h"
#include "util.h"
-int switch_root(const char *new_root, const char *oldroot, bool detach_oldroot, unsigned long mountflags) {
-
- /* Don't try to unmount/move the old "/", there's no way to do it. */
- static const char move_mounts[] =
- "/dev\0"
- "/proc\0"
- "/sys\0"
- "/run\0";
+int switch_root(const char *new_root,
+ const char *old_root_after, /* path below the new root, where to place the old root after the transition */
+ bool unmount_old_root,
+ unsigned long mount_flags) { /* MS_MOVE or MS_BIND */
+ _cleanup_free_ char *resolved_old_root_after = NULL;
_cleanup_close_ int old_root_fd = -1;
- struct stat new_root_stat;
bool old_root_remove;
- const char *i, *temporary_old_root;
+ const char *i;
+ int r;
+
+ assert(new_root);
+ assert(old_root_after);
if (path_equal(new_root, "/"))
return 0;
- temporary_old_root = strjoina(new_root, oldroot);
- mkdir_p_label(temporary_old_root, 0755);
-
+ /* Check if we shall remove the contents of the old root */
old_root_remove = in_initrd();
+ if (old_root_remove) {
+ old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY);
+ if (old_root_fd < 0)
+ return log_error_errno(errno, "Failed to open root directory: %m");
+ }
- if (stat(new_root, &new_root_stat) < 0)
- return log_error_errno(errno, "Failed to stat directory %s: %m", new_root);
+ /* Determine where we shall place the old root after the transition */
+ r = chase_symlinks(old_root_after, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &resolved_old_root_after);
+ if (r < 0)
+ return log_error_errno(r, "Failed to resolve %s/%s: %m", new_root, old_root_after);
+ if (r == 0) /* Doesn't exist yet. Let's create it */
+ (void) mkdir_p_label(resolved_old_root_after, 0755);
- /* Work-around for kernel design: the kernel refuses switching
- * root if any file systems are mounted MS_SHARED. Hence
+ /* Work-around for kernel design: the kernel refuses MS_MOVE if any file systems are mounted MS_SHARED. Hence
* remount them MS_PRIVATE here as a work-around.
*
* https://bugzilla.redhat.com/show_bug.cgi?id=847418 */
if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0)
- log_warning_errno(errno, "Failed to make \"/\" private mount: %m");
-
- NULSTR_FOREACH(i, move_mounts) {
- char new_mount[PATH_MAX];
- struct stat sb;
- size_t n;
-
- n = snprintf(new_mount, sizeof new_mount, "%s%s", new_root, i);
- if (n >= sizeof new_mount) {
- bool move = mountflags & MS_MOVE;
-
- log_warning("New path is too long, %s: %s%s",
- move ? "forcing unmount instead" : "ignoring",
- new_root, i);
-
- if (move)
- if (umount2(i, MNT_FORCE) < 0)
- log_warning_errno(errno, "Failed to unmount %s: %m", i);
- continue;
- }
-
- mkdir_p_label(new_mount, 0755);
-
- if (stat(new_mount, &sb) < 0 ||
- sb.st_dev != new_root_stat.st_dev) {
-
- /* Mount point seems to be mounted already or
- * stat failed. Unmount the old mount point. */
- if (umount2(i, MNT_DETACH) < 0)
- log_warning_errno(errno, "Failed to unmount %s: %m", i);
- continue;
- }
-
- if (mount(i, new_mount, NULL, mountflags, NULL) < 0) {
- if (mountflags & MS_MOVE) {
- log_error_errno(errno, "Failed to move mount %s to %s, forcing unmount: %m", i, new_mount);
-
- if (umount2(i, MNT_FORCE) < 0)
- log_warning_errno(errno, "Failed to unmount %s: %m", i);
-
- } else if (mountflags & MS_BIND)
- log_error_errno(errno, "Failed to bind mount %s to %s: %m", i, new_mount);
- }
+ return log_error_errno(errno, "Failed to set \"/\" mount propagation to private: %m");
+
+ FOREACH_STRING(i, "/sys", "/dev", "/run", "/proc") {
+ _cleanup_free_ char *chased = NULL;
+
+ r = chase_symlinks(i, new_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &chased);
+ if (r < 0)
+ return log_error_errno(r, "Failed to resolve %s/%s: %m", new_root, i);
+ if (r > 0) {
+ /* Already exists. Let's see if it is a mount point already. */
+ r = path_is_mount_point(chased, NULL, 0);
+ if (r < 0)
+ return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", chased);
+ if (r > 0) /* If it is already mounted, then do nothing */
+ continue;
+ } else
+ /* Doesn't exist yet? */
+ (void) mkdir_p_label(chased, 0755);
+
+ if (mount(i, chased, NULL, mount_flags, NULL) < 0)
+ return log_error_errno(r, "Failed to mount %s to %s: %m", i, chased);
}
- /* Do not fail, if base_filesystem_create() fails. Not all
- * switch roots are like base_filesystem_create() wants them
- * to look like. They might even boot, if they are RO and
- * don't have the FS layout. Just ignore the error and
- * switch_root() nevertheless. */
+ /* Do not fail if base_filesystem_create() fails. Not all switch roots are like base_filesystem_create() wants
+ * them to look like. They might even boot, if they are RO and don't have the FS layout. Just ignore the error
+ * and switch_root() nevertheless. */
(void) base_filesystem_create(new_root, UID_INVALID, GID_INVALID);
if (chdir(new_root) < 0)
return log_error_errno(errno, "Failed to change directory to %s: %m", new_root);
- if (old_root_remove) {
- old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY);
- if (old_root_fd < 0)
- log_warning_errno(errno, "Failed to open root directory: %m");
- }
-
- /* 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) {
+ /* 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, resolved_old_root_after) >= 0) {
/* Immediately get rid of the old root, if detach_oldroot is set.
* Since we are running off it we need to do this lazily. */
- if (detach_oldroot && umount2(oldroot, MNT_DETACH) < 0)
- log_error_errno(errno, "Failed to lazily umount old root dir %s, %s: %m",
- oldroot,
- errno == ENOENT ? "ignoring" : "leaving it around");
+ if (unmount_old_root) {
+ r = umount_recursive(old_root_after, MNT_DETACH);
+ if (r < 0)
+ log_warning_errno(r, "Failed to unmount old root directory tree, ignoring: %m");
+ }
} else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0)
- return log_error_errno(errno, "Failed to mount moving %s to /: %m", new_root);
+ return log_error_errno(errno, "Failed to move %s to /: %m", new_root);
if (chroot(".") < 0)
return log_error_errno(errno, "Failed to change root: %m");
projects / thirdparty / systemd.git / blobdiff