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 /* skip if device is not the same */
98 if (sb
.st_dev
!= rb
.st_dev
)
101 /* remove subdirectories */
102 if (S_ISDIR(sb
.st_mode
)) {
105 cfd
= openat(dfd
, d
->d_name
, O_RDONLY
);
107 recursiveRemove(cfd
);
114 if (unlinkat(dfd
, d
->d_name
, isdir
? AT_REMOVEDIR
: 0))
115 warn(_("failed to unlink %s"), d
->d_name
);
118 rc
= 0; /* success */
126 static int switchroot(const char *newroot
)
128 /* Don't try to unmount the old "/", there's no way to do it. */
129 const char *umounts
[] = { "/dev", "/proc", "/sys", "/run", NULL
};
133 struct stat newroot_stat
, sb
;
135 if (stat(newroot
, &newroot_stat
) != 0) {
136 warn(_("stat of %s failed"), newroot
);
140 for (i
= 0; umounts
[i
] != NULL
; i
++) {
141 char newmount
[PATH_MAX
];
143 snprintf(newmount
, sizeof(newmount
), "%s%s", newroot
, umounts
[i
]);
145 if ((stat(newmount
, &sb
) != 0) || (sb
.st_dev
!= newroot_stat
.st_dev
)) {
146 /* mount point seems to be mounted already or stat failed */
147 umount2(umounts
[i
], MNT_DETACH
);
151 if (mount(umounts
[i
], newmount
, NULL
, MS_MOVE
, NULL
) < 0) {
152 warn(_("failed to mount moving %s to %s"),
153 umounts
[i
], newmount
);
154 warnx(_("forcing unmount of %s"), umounts
[i
]);
155 umount2(umounts
[i
], MNT_FORCE
);
159 if (chdir(newroot
)) {
160 warn(_("failed to change directory to %s"), newroot
);
164 cfd
= open("/", O_RDONLY
);
166 warn(_("cannot open %s"), "/");
170 if (mount(newroot
, "/", NULL
, MS_MOVE
, NULL
) < 0) {
172 warn(_("failed to mount moving %s to /"), newroot
);
178 warn(_("failed to change root"));
186 if (fstatfs(cfd
, &stfs
) == 0 &&
187 (F_TYPE_EQUAL(stfs
.f_type
, STATFS_RAMFS_MAGIC
) ||
188 F_TYPE_EQUAL(stfs
.f_type
, STATFS_TMPFS_MAGIC
)))
189 recursiveRemove(cfd
);
191 warn(_("old root filesystem is not an initramfs"));
200 static void __attribute__((__noreturn__
)) usage(FILE *output
)
202 fputs(USAGE_HEADER
, output
);
203 fprintf(output
, _(" %s [options] <newrootdir> <init> <args to init>\n"),
204 program_invocation_short_name
);
206 fputs(USAGE_SEPARATOR
, output
);
207 fputs(_("Switch to another filesystem as the root of the mount tree.\n"), output
);
209 fputs(USAGE_OPTIONS
, output
);
210 fputs(USAGE_HELP
, output
);
211 fputs(USAGE_VERSION
, output
);
212 fprintf(output
, USAGE_MAN_TAIL("switch_root(8)"));
214 exit(output
== stderr
? EXIT_FAILURE
: EXIT_SUCCESS
);
217 int main(int argc
, char *argv
[])
219 char *newroot
, *init
, **initargs
;
220 atexit(close_stdout
);
222 if (argv
[1] && (!strcmp(argv
[1], "--help") || !strcmp(argv
[1], "-h")))
224 if (argv
[1] && (!strcmp(argv
[1], "--version") || !strcmp(argv
[1], "-V"))) {
225 printf(UTIL_LINUX_VERSION
);
235 if (!*newroot
|| !*init
)
238 if (switchroot(newroot
))
239 errx(EXIT_FAILURE
, _("failed. Sorry."));
241 if (access(init
, X_OK
))
242 warn(_("cannot access %s"), init
);
244 execv(init
, initargs
);
245 err(EXIT_FAILURE
, _("failed to execute %s"), init
);