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41669317 LP |
1 | /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2012 Harald Hoyer, Lennart Poettering | |
7 | ||
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. | |
12 | ||
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. | |
17 | ||
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/>. | |
20 | ***/ | |
21 | ||
22 | #include <sys/stat.h> | |
23 | #include <stdbool.h> | |
24 | #include <errno.h> | |
25 | #include <string.h> | |
26 | #include <sys/mount.h> | |
27 | #include <unistd.h> | |
28 | #include <fcntl.h> | |
29 | ||
30 | #include "util.h" | |
31 | #include "path-util.h" | |
32 | #include "switch-root.h" | |
971ff8c7 KS |
33 | #include "mkdir.h" |
34 | #include "base-filesystem.h" | |
891a4918 | 35 | #include "missing.h" |
41669317 | 36 | |
5a4bf02f | 37 | int switch_root(const char *new_root, const char *oldroot, bool detach_oldroot, unsigned long mountflags) { |
41669317 LP |
38 | |
39 | /* Don't try to unmount/move the old "/", there's no way to do it. */ | |
40 | static const char move_mounts[] = | |
41 | "/dev\0" | |
42 | "/proc\0" | |
43 | "/sys\0" | |
44 | "/run\0"; | |
45 | ||
03e334a1 | 46 | _cleanup_close_ int old_root_fd = -1; |
41669317 LP |
47 | struct stat new_root_stat; |
48 | bool old_root_remove; | |
03e334a1 | 49 | const char *i, *temporary_old_root; |
41669317 LP |
50 | |
51 | if (path_equal(new_root, "/")) | |
52 | return 0; | |
53 | ||
5a4bf02f HH |
54 | temporary_old_root = strappenda(new_root, oldroot); |
55 | mkdir_p_label(temporary_old_root, 0755); | |
891a4918 | 56 | |
41669317 LP |
57 | old_root_remove = in_initrd(); |
58 | ||
59 | if (stat(new_root, &new_root_stat) < 0) { | |
56f64d95 | 60 | log_error_errno(errno, "Failed to stat directory %s: %m", new_root); |
03e334a1 | 61 | return -errno; |
41669317 LP |
62 | } |
63 | ||
d677d4df ZJS |
64 | /* Work-around for kernel design: the kernel refuses switching |
65 | * root if any file systems are mounted MS_SHARED. Hence | |
66 | * remount them MS_PRIVATE here as a work-around. | |
f47fc355 LP |
67 | * |
68 | * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */ | |
69 | if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0) | |
56f64d95 | 70 | log_warning_errno(errno, "Failed to make \"/\" private mount: %m"); |
f47fc355 | 71 | |
41669317 LP |
72 | NULSTR_FOREACH(i, move_mounts) { |
73 | char new_mount[PATH_MAX]; | |
74 | struct stat sb; | |
75 | ||
76 | snprintf(new_mount, sizeof(new_mount), "%s%s", new_root, i); | |
77 | char_array_0(new_mount); | |
78 | ||
5a4bf02f | 79 | mkdir_p_label(new_mount, 0755); |
971ff8c7 | 80 | |
41669317 LP |
81 | if ((stat(new_mount, &sb) < 0) || |
82 | sb.st_dev != new_root_stat.st_dev) { | |
83 | ||
84 | /* Mount point seems to be mounted already or | |
85 | * stat failed. Unmount the old mount | |
86 | * point. */ | |
87 | if (umount2(i, MNT_DETACH) < 0) | |
56f64d95 | 88 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
41669317 LP |
89 | continue; |
90 | } | |
91 | ||
5a4bf02f HH |
92 | if (mount(i, new_mount, NULL, mountflags, NULL) < 0) { |
93 | if (mountflags & MS_MOVE) { | |
56f64d95 | 94 | log_error_errno(errno, "Failed to move mount %s to %s, forcing unmount: %m", i, new_mount); |
5a4bf02f HH |
95 | |
96 | if (umount2(i, MNT_FORCE) < 0) | |
56f64d95 | 97 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
5a4bf02f HH |
98 | } |
99 | if (mountflags & MS_BIND) | |
56f64d95 | 100 | log_error_errno(errno, "Failed to bind mount %s to %s: %m", i, new_mount); |
41669317 | 101 | |
41669317 LP |
102 | } |
103 | } | |
104 | ||
64e18fd6 LP |
105 | /* Do not fail, if base_filesystem_create() fails. Not all |
106 | * switch roots are like base_filesystem_create() wants them | |
107 | * to look like. They might even boot, if they are RO and | |
108 | * don't have the FS layout. Just ignore the error and | |
109 | * switch_root() nevertheless. */ | |
6d0f91bf | 110 | (void) base_filesystem_create(new_root); |
971ff8c7 | 111 | |
41669317 | 112 | if (chdir(new_root) < 0) { |
56f64d95 | 113 | log_error_errno(errno, "Failed to change directory to %s: %m", new_root); |
03e334a1 | 114 | return -errno; |
41669317 LP |
115 | } |
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 LP |
134 | |
135 | } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) { | |
56f64d95 | 136 | log_error_errno(errno, "Failed to mount moving %s to /: %m", new_root); |
03e334a1 | 137 | return -errno; |
41669317 LP |
138 | } |
139 | ||
140 | if (chroot(".") < 0) { | |
56f64d95 | 141 | log_error_errno(errno, "Failed to change root: %m"); |
03e334a1 | 142 | return -errno; |
41669317 LP |
143 | } |
144 | ||
ac0930c8 | 145 | if (chdir("/") < 0) { |
56f64d95 | 146 | log_error_errno(errno, "Failed to change directory: %m"); |
03e334a1 | 147 | return -errno; |
ac0930c8 LP |
148 | } |
149 | ||
41669317 LP |
150 | if (old_root_fd >= 0) { |
151 | struct stat rb; | |
152 | ||
153 | if (fstat(old_root_fd, &rb) < 0) | |
56f64d95 | 154 | log_warning_errno(errno, "Failed to stat old root directory, leaving: %m"); |
b46178e5 | 155 | else { |
41669317 | 156 | rm_rf_children(old_root_fd, false, false, &rb); |
b46178e5 HH |
157 | old_root_fd = -1; |
158 | } | |
41669317 LP |
159 | } |
160 | ||
03e334a1 | 161 | return 0; |
41669317 | 162 | } |