1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
4 This file is part of systemd.
6 Copyright 2012 Harald Hoyer, Lennart Poettering
8 systemd is free software; you can redistribute it and/or modify it
9 under the terms of the GNU Lesser General Public License as published by
10 the Free Software Foundation; either version 2.1 of the License, or
11 (at your option) any later version.
13 systemd is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 Lesser General Public License for more details.
18 You should have received a copy of the GNU Lesser General Public License
19 along with systemd; If not, see <http://www.gnu.org/licenses/>.
26 #include <sys/mount.h>
31 #include "path-util.h"
32 #include "switch-root.h"
34 int switch_root(const char *new_root) {
36 /* Don't try to unmount/move the old "/", there's no way to do it. */
37 static const char move_mounts[] =
43 int r, old_root_fd = -1;
44 struct stat new_root_stat;
48 if (path_equal(new_root, "/"))
51 old_root_remove = in_initrd();
53 if (stat(new_root, &new_root_stat) < 0) {
55 log_error("Failed to stat directory %s: %m", new_root);
59 /* Work-around for a kernel bug: for some reason the kernel
60 * refuses switching root if any file systems are mounted
61 * MS_SHARED. Hence remount them MS_PRIVATE here as a
64 * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */
65 if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0)
66 log_warning("Failed to make \"/\" private mount: %m");
68 NULSTR_FOREACH(i, move_mounts) {
69 char new_mount[PATH_MAX];
72 snprintf(new_mount, sizeof(new_mount), "%s%s", new_root, i);
73 char_array_0(new_mount);
75 if ((stat(new_mount, &sb) < 0) ||
76 sb.st_dev != new_root_stat.st_dev) {
78 /* Mount point seems to be mounted already or
79 * stat failed. Unmount the old mount
81 if (umount2(i, MNT_DETACH) < 0)
82 log_warning("Failed to unmount %s: %m", i);
86 if (mount(i, new_mount, NULL, MS_MOVE, NULL) < 0) {
87 log_error("Failed to move mount %s to %s, forcing unmount: %m", i, new_mount);
89 if (umount2(i, MNT_FORCE) < 0)
90 log_warning("Failed to unmount %s: %m", i);
94 if (chdir(new_root) < 0) {
96 log_error("Failed to change directory to %s: %m", new_root);
100 if (old_root_remove) {
101 old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY);
103 log_warning("Failed to open root directory: %m");
106 if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) {
108 log_error("Failed to mount moving %s to /: %m", new_root);
112 if (chroot(".") < 0) {
114 log_error("Failed to change root: %m");
118 if (chdir("/") < 0) {
120 log_error("Failed to change directory: %m");
124 if (old_root_fd >= 0) {
127 if (fstat(old_root_fd, &rb) < 0)
128 log_warning("Failed to stat old root directory, leaving: %m");
130 rm_rf_children(old_root_fd, false, false, &rb);
138 if (old_root_fd >= 0)
139 close_nointr_nofail(old_root_fd);