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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 | ||
41669317 | 22 | #include <errno.h> |
07630cea LP |
23 | #include <fcntl.h> |
24 | #include <stdbool.h> | |
41669317 LP |
25 | #include <string.h> |
26 | #include <sys/mount.h> | |
07630cea | 27 | #include <sys/stat.h> |
41669317 | 28 | #include <unistd.h> |
41669317 | 29 | |
971ff8c7 | 30 | #include "base-filesystem.h" |
891a4918 | 31 | #include "missing.h" |
07630cea LP |
32 | #include "mkdir.h" |
33 | #include "path-util.h" | |
34 | #include "rm-rf.h" | |
35 | #include "string-util.h" | |
36 | #include "util.h" | |
c6878637 | 37 | #include "switch-root.h" |
41669317 | 38 | |
5a4bf02f | 39 | int switch_root(const char *new_root, const char *oldroot, bool detach_oldroot, unsigned long mountflags) { |
41669317 LP |
40 | |
41 | /* Don't try to unmount/move the old "/", there's no way to do it. */ | |
42 | static const char move_mounts[] = | |
43 | "/dev\0" | |
44 | "/proc\0" | |
45 | "/sys\0" | |
46 | "/run\0"; | |
47 | ||
03e334a1 | 48 | _cleanup_close_ int old_root_fd = -1; |
41669317 LP |
49 | struct stat new_root_stat; |
50 | bool old_root_remove; | |
03e334a1 | 51 | const char *i, *temporary_old_root; |
41669317 LP |
52 | |
53 | if (path_equal(new_root, "/")) | |
54 | return 0; | |
55 | ||
63c372cb | 56 | temporary_old_root = strjoina(new_root, oldroot); |
5a4bf02f | 57 | mkdir_p_label(temporary_old_root, 0755); |
891a4918 | 58 | |
41669317 LP |
59 | old_root_remove = in_initrd(); |
60 | ||
4a62c710 MS |
61 | if (stat(new_root, &new_root_stat) < 0) |
62 | return log_error_errno(errno, "Failed to stat directory %s: %m", new_root); | |
41669317 | 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); | |
41669317 | 77 | |
5a4bf02f | 78 | mkdir_p_label(new_mount, 0755); |
971ff8c7 | 79 | |
41669317 LP |
80 | if ((stat(new_mount, &sb) < 0) || |
81 | sb.st_dev != new_root_stat.st_dev) { | |
82 | ||
83 | /* Mount point seems to be mounted already or | |
84 | * stat failed. Unmount the old mount | |
85 | * point. */ | |
86 | if (umount2(i, MNT_DETACH) < 0) | |
56f64d95 | 87 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
41669317 LP |
88 | continue; |
89 | } | |
90 | ||
5a4bf02f HH |
91 | if (mount(i, new_mount, NULL, mountflags, NULL) < 0) { |
92 | if (mountflags & MS_MOVE) { | |
56f64d95 | 93 | log_error_errno(errno, "Failed to move mount %s to %s, forcing unmount: %m", i, new_mount); |
5a4bf02f HH |
94 | |
95 | if (umount2(i, MNT_FORCE) < 0) | |
56f64d95 | 96 | log_warning_errno(errno, "Failed to unmount %s: %m", i); |
5a4bf02f HH |
97 | } |
98 | if (mountflags & MS_BIND) | |
56f64d95 | 99 | log_error_errno(errno, "Failed to bind mount %s to %s: %m", i, new_mount); |
41669317 | 100 | |
41669317 LP |
101 | } |
102 | } | |
103 | ||
64e18fd6 LP |
104 | /* Do not fail, if base_filesystem_create() fails. Not all |
105 | * switch roots are like base_filesystem_create() wants them | |
106 | * to look like. They might even boot, if they are RO and | |
107 | * don't have the FS layout. Just ignore the error and | |
108 | * switch_root() nevertheless. */ | |
03cfe0d5 | 109 | (void) base_filesystem_create(new_root, UID_INVALID, GID_INVALID); |
971ff8c7 | 110 | |
4a62c710 MS |
111 | if (chdir(new_root) < 0) |
112 | return log_error_errno(errno, "Failed to change directory to %s: %m", new_root); | |
41669317 LP |
113 | |
114 | if (old_root_remove) { | |
115 | old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY); | |
116 | if (old_root_fd < 0) | |
56f64d95 | 117 | log_warning_errno(errno, "Failed to open root directory: %m"); |
41669317 LP |
118 | } |
119 | ||
891a4918 LP |
120 | /* We first try a pivot_root() so that we can umount the old |
121 | * root dir. In many cases (i.e. where rootfs is /), that's | |
122 | * not possible however, and hence we simply overmount root */ | |
123 | if (pivot_root(new_root, temporary_old_root) >= 0) { | |
124 | ||
5a4bf02f HH |
125 | /* Immediately get rid of the old root, if detach_oldroot is set. |
126 | * Since we are running off it we need to do this lazily. */ | |
d677d4df | 127 | if (detach_oldroot && umount2(oldroot, MNT_DETACH) < 0) |
56f64d95 | 128 | log_error_errno(errno, "Failed to lazily umount old root dir %s, %s: %m", |
d677d4df ZJS |
129 | oldroot, |
130 | errno == ENOENT ? "ignoring" : "leaving it around"); | |
891a4918 | 131 | |
4a62c710 MS |
132 | } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) |
133 | return log_error_errno(errno, "Failed to mount moving %s to /: %m", new_root); | |
41669317 | 134 | |
4a62c710 MS |
135 | if (chroot(".") < 0) |
136 | return log_error_errno(errno, "Failed to change root: %m"); | |
41669317 | 137 | |
4a62c710 MS |
138 | if (chdir("/") < 0) |
139 | return log_error_errno(errno, "Failed to change directory: %m"); | |
ac0930c8 | 140 | |
41669317 LP |
141 | if (old_root_fd >= 0) { |
142 | struct stat rb; | |
143 | ||
144 | if (fstat(old_root_fd, &rb) < 0) | |
56f64d95 | 145 | log_warning_errno(errno, "Failed to stat old root directory, leaving: %m"); |
b46178e5 | 146 | else { |
c6878637 | 147 | (void) rm_rf_children(old_root_fd, 0, &rb); |
b46178e5 HH |
148 | old_root_fd = -1; |
149 | } | |
41669317 LP |
150 | } |
151 | ||
03e334a1 | 152 | return 0; |
41669317 | 153 | } |