2 * switchroot.c - switch to new root directory and start init.
4 * Copyright 2002-2009 Red Hat, Inc. All rights reserved.
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
20 * Peter Jones <pjones@redhat.com>
21 * Jeremy Katz <katzj@redhat.com>
23 #include <sys/mount.h>
24 #include <sys/types.h>
26 #include <sys/statfs.h>
27 #include <sys/param.h>
39 #include "closestream.h"
40 #include "statfs_magic.h"
47 #define MNT_DETACH 0x00000002 /* Just detach from the tree */
50 /* remove all files/directories below dirName -- don't cross mountpoints */
51 static int recursiveRemove(int fd
)
58 if (!(dir
= fdopendir(fd
))) {
59 warn(_("failed to open directory"));
63 /* fdopendir() precludes us from continuing to use the input fd */
66 if (fstat(dfd
, &rb
)) {
67 warn(_("stat failed"));
76 if (!(d
= readdir(dir
))) {
78 warn(_("failed to read directory"));
81 break; /* end of directory */
84 if (!strcmp(d
->d_name
, ".") || !strcmp(d
->d_name
, ".."))
86 #ifdef _DIRENT_HAVE_D_TYPE
87 if (d
->d_type
== DT_DIR
|| d
->d_type
== DT_UNKNOWN
)
92 if (fstatat(dfd
, d
->d_name
, &sb
, AT_SYMLINK_NOFOLLOW
)) {
93 warn(_("stat of %s failed"), d
->d_name
);
97 /* remove subdirectories if device is same as dir */
98 if (S_ISDIR(sb
.st_mode
) && sb
.st_dev
== rb
.st_dev
) {
101 cfd
= openat(dfd
, d
->d_name
, O_RDONLY
);
103 recursiveRemove(cfd
);
111 if (unlinkat(dfd
, d
->d_name
, isdir
? AT_REMOVEDIR
: 0))
112 warn(_("failed to unlink %s"), d
->d_name
);
115 rc
= 0; /* success */
123 static int switchroot(const char *newroot
)
125 /* Don't try to unmount the old "/", there's no way to do it. */
126 const char *umounts
[] = { "/dev", "/proc", "/sys", "/run", NULL
};
130 struct stat newroot_stat
, sb
;
132 if (stat(newroot
, &newroot_stat
) != 0) {
133 warn(_("stat of %s failed"), newroot
);
137 for (i
= 0; umounts
[i
] != NULL
; i
++) {
138 char newmount
[PATH_MAX
];
140 snprintf(newmount
, sizeof(newmount
), "%s%s", newroot
, umounts
[i
]);
142 if ((stat(newmount
, &sb
) != 0) || (sb
.st_dev
!= newroot_stat
.st_dev
)) {
143 /* mount point seems to be mounted already or stat failed */
144 umount2(umounts
[i
], MNT_DETACH
);
148 if (mount(umounts
[i
], newmount
, NULL
, MS_MOVE
, NULL
) < 0) {
149 warn(_("failed to mount moving %s to %s"),
150 umounts
[i
], newmount
);
151 warnx(_("forcing unmount of %s"), umounts
[i
]);
152 umount2(umounts
[i
], MNT_FORCE
);
156 if (chdir(newroot
)) {
157 warn(_("failed to change directory to %s"), newroot
);
161 cfd
= open("/", O_RDONLY
);
163 warn(_("cannot open %s"), "/");
167 if (mount(newroot
, "/", NULL
, MS_MOVE
, NULL
) < 0) {
169 warn(_("failed to mount moving %s to /"), newroot
);
175 warn(_("failed to change root"));
183 if (fstatfs(cfd
, &stfs
) == 0 &&
184 (F_TYPE_EQUAL(stfs
.f_type
, STATFS_RAMFS_MAGIC
) ||
185 F_TYPE_EQUAL(stfs
.f_type
, STATFS_TMPFS_MAGIC
)))
186 recursiveRemove(cfd
);
188 warn(_("old root filesystem is not an initramfs"));
197 static void __attribute__((__noreturn__
)) usage(FILE *output
)
199 fputs(USAGE_HEADER
, output
);
200 fprintf(output
, _(" %s [options] <newrootdir> <init> <args to init>\n"),
201 program_invocation_short_name
);
203 fputs(USAGE_SEPARATOR
, output
);
204 fputs(_("Switch to another filesystem as the root of the mount tree.\n"), output
);
206 fputs(USAGE_OPTIONS
, output
);
207 fputs(USAGE_HELP
, output
);
208 fputs(USAGE_VERSION
, output
);
209 fprintf(output
, USAGE_MAN_TAIL("switch_root(8)"));
211 exit(output
== stderr
? EXIT_FAILURE
: EXIT_SUCCESS
);
214 int main(int argc
, char *argv
[])
216 char *newroot
, *init
, **initargs
;
217 atexit(close_stdout
);
219 if (argv
[1] && (!strcmp(argv
[1], "--help") || !strcmp(argv
[1], "-h")))
221 if (argv
[1] && (!strcmp(argv
[1], "--version") || !strcmp(argv
[1], "-V"))) {
222 printf(UTIL_LINUX_VERSION
);
232 if (!*newroot
|| !*init
)
235 if (switchroot(newroot
))
236 errx(EXIT_FAILURE
, _("failed. Sorry."));
238 if (access(init
, X_OK
))
239 warn(_("cannot access %s"), init
);
241 execv(init
, initargs
);
242 err(EXIT_FAILURE
, _("failed to execute %s"), init
);