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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" | |
33 | ||
34 | int switch_root(const char *new_root) { | |
35 | ||
36 | /* Don't try to unmount/move the old "/", there's no way to do it. */ | |
37 | static const char move_mounts[] = | |
38 | "/dev\0" | |
39 | "/proc\0" | |
40 | "/sys\0" | |
41 | "/run\0"; | |
42 | ||
43 | int r, old_root_fd = -1; | |
44 | struct stat new_root_stat; | |
45 | bool old_root_remove; | |
46 | const char *i; | |
47 | ||
48 | if (path_equal(new_root, "/")) | |
49 | return 0; | |
50 | ||
51 | old_root_remove = in_initrd(); | |
52 | ||
53 | if (stat(new_root, &new_root_stat) < 0) { | |
54 | r = -errno; | |
55 | log_error("Failed to stat directory %s: %m", new_root); | |
56 | goto fail; | |
57 | } | |
58 | ||
59 | NULSTR_FOREACH(i, move_mounts) { | |
60 | char new_mount[PATH_MAX]; | |
61 | struct stat sb; | |
62 | ||
63 | snprintf(new_mount, sizeof(new_mount), "%s%s", new_root, i); | |
64 | char_array_0(new_mount); | |
65 | ||
66 | if ((stat(new_mount, &sb) < 0) || | |
67 | sb.st_dev != new_root_stat.st_dev) { | |
68 | ||
69 | /* Mount point seems to be mounted already or | |
70 | * stat failed. Unmount the old mount | |
71 | * point. */ | |
72 | if (umount2(i, MNT_DETACH) < 0) | |
73 | log_warning("Failed to unmount %s: %m", i); | |
74 | continue; | |
75 | } | |
76 | ||
77 | if (mount(i, new_mount, NULL, MS_MOVE, NULL) < 0) { | |
78 | log_error("Failed to move mount %s to %s, forcing unmount: %m", i, new_mount); | |
79 | ||
80 | if (umount2(i, MNT_FORCE) < 0) | |
81 | log_warning("Failed to unmount %s: %m", i); | |
82 | } | |
83 | } | |
84 | ||
85 | if (chdir(new_root) < 0) { | |
86 | r = -errno; | |
87 | log_error("Failed to change directory to %s: %m", new_root); | |
88 | goto fail; | |
89 | } | |
90 | ||
91 | if (old_root_remove) { | |
92 | old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY); | |
93 | if (old_root_fd < 0) | |
94 | log_warning("Failed to open root directory: %m"); | |
95 | } | |
96 | ||
97 | if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) { | |
98 | r = -errno; | |
99 | log_error("Failed to mount moving %s to /: %m", new_root); | |
100 | goto fail; | |
101 | } | |
102 | ||
103 | if (chroot(".") < 0) { | |
104 | r = -errno; | |
105 | log_error("Failed to change root: %m"); | |
106 | goto fail; | |
107 | } | |
108 | ||
109 | if (old_root_fd >= 0) { | |
110 | struct stat rb; | |
111 | ||
112 | if (fstat(old_root_fd, &rb) < 0) | |
113 | log_warning("Failed to stat old root directory, leaving: %m"); | |
114 | else | |
115 | rm_rf_children(old_root_fd, false, false, &rb); | |
116 | } | |
117 | ||
118 | r = 0; | |
119 | ||
120 | fail: | |
121 | if (old_root_fd >= 0) | |
122 | close_nointr_nofail(old_root_fd); | |
123 | ||
124 | return r; | |
125 | } |