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Commit | Line | Data |
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41669317 LP |
1 | /*** |
2 | This file is part of systemd. | |
3 | ||
4 | Copyright 2012 Harald Hoyer, Lennart Poettering | |
5 | ||
6 | systemd is free software; you can redistribute it and/or modify it | |
7 | under the terms of the GNU Lesser General Public License as published by | |
8 | the Free Software Foundation; either version 2.1 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | systemd is distributed in the hope that it will be useful, but | |
12 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public License | |
17 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
18 | ***/ | |
19 | ||
41669317 | 20 | #include <errno.h> |
07630cea | 21 | #include <fcntl.h> |
a8fbdf54 | 22 | #include <limits.h> |
07630cea | 23 | #include <stdbool.h> |
a8fbdf54 | 24 | #include <stdio.h> |
41669317 | 25 | #include <sys/mount.h> |
07630cea | 26 | #include <sys/stat.h> |
41669317 | 27 | #include <unistd.h> |
41669317 | 28 | |
971ff8c7 | 29 | #include "base-filesystem.h" |
3ffd4af2 | 30 | #include "fd-util.h" |
a8fbdf54 | 31 | #include "log.h" |
891a4918 | 32 | #include "missing.h" |
07630cea LP |
33 | #include "mkdir.h" |
34 | #include "path-util.h" | |
35 | #include "rm-rf.h" | |
d054f0a4 | 36 | #include "stdio-util.h" |
07630cea | 37 | #include "string-util.h" |
c6878637 | 38 | #include "switch-root.h" |
ee104e11 | 39 | #include "user-util.h" |
3ffd4af2 | 40 | #include "util.h" |
41669317 | 41 | |
5a4bf02f | 42 | int switch_root(const char *new_root, const char *oldroot, bool detach_oldroot, unsigned long mountflags) { |
41669317 LP |
43 | |
44 | /* Don't try to unmount/move the old "/", there's no way to do it. */ | |
45 | static const char move_mounts[] = | |
46 | "/dev\0" | |
47 | "/proc\0" | |
48 | "/sys\0" | |
49 | "/run\0"; | |
50 | ||
03e334a1 | 51 | _cleanup_close_ int old_root_fd = -1; |
41669317 LP |
52 | struct stat new_root_stat; |
53 | bool old_root_remove; | |
03e334a1 | 54 | const char *i, *temporary_old_root; |
41669317 LP |
55 | |
56 | if (path_equal(new_root, "/")) | |
57 | return 0; | |
58 | ||
63c372cb | 59 | temporary_old_root = strjoina(new_root, oldroot); |
5a4bf02f | 60 | mkdir_p_label(temporary_old_root, 0755); |
891a4918 | 61 | |
41669317 LP |
62 | old_root_remove = in_initrd(); |
63 | ||
4a62c710 MS |
64 | if (stat(new_root, &new_root_stat) < 0) |
65 | return log_error_errno(errno, "Failed to stat directory %s: %m", new_root); | |
41669317 | 66 | |
d677d4df ZJS |
67 | /* Work-around for kernel design: the kernel refuses switching |
68 | * root if any file systems are mounted MS_SHARED. Hence | |
69 | * remount them MS_PRIVATE here as a work-around. | |
f47fc355 LP |
70 | * |
71 | * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */ | |
72 | if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0) | |
56f64d95 | 73 | log_warning_errno(errno, "Failed to make \"/\" private mount: %m"); |
f47fc355 | 74 | |
41669317 LP |
75 | NULSTR_FOREACH(i, move_mounts) { |
76 | char new_mount[PATH_MAX]; | |
77 | struct stat sb; | |
78 | ||
d054f0a4 | 79 | xsprintf(new_mount, "%s%s", new_root, i); |
41669317 | 80 | |
5a4bf02f | 81 | mkdir_p_label(new_mount, 0755); |
971ff8c7 | 82 | |
41669317 LP |
83 | if ((stat(new_mount, &sb) < 0) || |
84 | sb.st_dev != new_root_stat.st_dev) { | |
85 | ||
86 | /* Mount point seems to be mounted already or | |
87 | * stat failed. Unmount the old mount | |
88 | * point. */ | |
89 | if (umount2(i, MNT_DETACH) < 0) | |
56f64d95 | 90 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
41669317 LP |
91 | continue; |
92 | } | |
93 | ||
5a4bf02f HH |
94 | if (mount(i, new_mount, NULL, mountflags, NULL) < 0) { |
95 | if (mountflags & MS_MOVE) { | |
56f64d95 | 96 | log_error_errno(errno, "Failed to move mount %s to %s, forcing unmount: %m", i, new_mount); |
5a4bf02f HH |
97 | |
98 | if (umount2(i, MNT_FORCE) < 0) | |
56f64d95 | 99 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
5a4bf02f HH |
100 | } |
101 | if (mountflags & MS_BIND) | |
56f64d95 | 102 | log_error_errno(errno, "Failed to bind mount %s to %s: %m", i, new_mount); |
41669317 | 103 | |
41669317 LP |
104 | } |
105 | } | |
106 | ||
64e18fd6 LP |
107 | /* Do not fail, if base_filesystem_create() fails. Not all |
108 | * switch roots are like base_filesystem_create() wants them | |
109 | * to look like. They might even boot, if they are RO and | |
110 | * don't have the FS layout. Just ignore the error and | |
111 | * switch_root() nevertheless. */ | |
03cfe0d5 | 112 | (void) base_filesystem_create(new_root, UID_INVALID, GID_INVALID); |
971ff8c7 | 113 | |
4a62c710 MS |
114 | if (chdir(new_root) < 0) |
115 | return log_error_errno(errno, "Failed to change directory to %s: %m", new_root); | |
41669317 LP |
116 | |
117 | if (old_root_remove) { | |
118 | old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY); | |
119 | if (old_root_fd < 0) | |
56f64d95 | 120 | log_warning_errno(errno, "Failed to open root directory: %m"); |
41669317 LP |
121 | } |
122 | ||
891a4918 LP |
123 | /* We first try a pivot_root() so that we can umount the old |
124 | * root dir. In many cases (i.e. where rootfs is /), that's | |
125 | * not possible however, and hence we simply overmount root */ | |
126 | if (pivot_root(new_root, temporary_old_root) >= 0) { | |
127 | ||
5a4bf02f HH |
128 | /* Immediately get rid of the old root, if detach_oldroot is set. |
129 | * Since we are running off it we need to do this lazily. */ | |
d677d4df | 130 | if (detach_oldroot && umount2(oldroot, MNT_DETACH) < 0) |
56f64d95 | 131 | log_error_errno(errno, "Failed to lazily umount old root dir %s, %s: %m", |
d677d4df ZJS |
132 | oldroot, |
133 | errno == ENOENT ? "ignoring" : "leaving it around"); | |
891a4918 | 134 | |
4a62c710 MS |
135 | } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) |
136 | return log_error_errno(errno, "Failed to mount moving %s to /: %m", new_root); | |
41669317 | 137 | |
4a62c710 MS |
138 | if (chroot(".") < 0) |
139 | return log_error_errno(errno, "Failed to change root: %m"); | |
41669317 | 140 | |
4a62c710 MS |
141 | if (chdir("/") < 0) |
142 | return log_error_errno(errno, "Failed to change directory: %m"); | |
ac0930c8 | 143 | |
41669317 LP |
144 | if (old_root_fd >= 0) { |
145 | struct stat rb; | |
146 | ||
147 | if (fstat(old_root_fd, &rb) < 0) | |
56f64d95 | 148 | log_warning_errno(errno, "Failed to stat old root directory, leaving: %m"); |
b46178e5 | 149 | else { |
c6878637 | 150 | (void) rm_rf_children(old_root_fd, 0, &rb); |
b46178e5 HH |
151 | old_root_fd = -1; |
152 | } | |
41669317 LP |
153 | } |
154 | ||
03e334a1 | 155 | return 0; |
41669317 | 156 | } |