1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
|
/*
* switchroot.c - switch to new root directory and start init.
*
* Copyright 2002-2008 Red Hat, Inc. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Authors:
* Peter Jones <pjones@redhat.com>
* Jeremy Katz <katzj@redhat.com>
*/
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/param.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <dirent.h>
#ifndef MS_MOVE
#define MS_MOVE 8192
#endif
enum {
ok,
err_no_directory,
err_usage,
};
/* remove all files/directories below dirName -- don't cross mountpoints */
static int
recursiveRemove(char * dirName)
{
struct stat sb,rb;
DIR * dir;
struct dirent * d;
char * strBuf = alloca(strlen(dirName) + 1024);
if (!(dir = opendir(dirName))) {
printf("error opening %s: %m\n", dirName);
return 0;
}
if (fstat(dirfd(dir),&rb)) {
printf("unable to stat %s: %m\n", dirName);
closedir(dir);
return 0;
}
errno = 0;
while ((d = readdir(dir))) {
errno = 0;
if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, "..")) {
errno = 0;
continue;
}
strcpy(strBuf, dirName);
strcat(strBuf, "/");
strcat(strBuf, d->d_name);
if (lstat(strBuf, &sb)) {
printf("failed to stat %s: %m\n", strBuf);
errno = 0;
continue;
}
/* only descend into subdirectories if device is same as dir */
if (S_ISDIR(sb.st_mode)) {
if (sb.st_dev == rb.st_dev) {
recursiveRemove(strBuf);
if (rmdir(strBuf))
printf("failed to rmdir %s: %m\n", strBuf);
}
errno = 0;
continue;
}
if (unlink(strBuf)) {
printf("failed to remove %s: %m\n", strBuf);
errno = 0;
continue;
}
}
if (errno) {
closedir(dir);
printf("error reading from %s: %m\n", dirName);
return 1;
}
closedir(dir);
return 0;
}
static int switchroot(const char *newroot)
{
/* Don't try to unmount the old "/", there's no way to do it. */
const char *umounts[] = { "/dev", "/proc", "/sys", NULL };
int errnum;
int i;
for (i = 0; umounts[i] != NULL; i++) {
char newmount[PATH_MAX];
strcpy(newmount, newroot);
strcat(newmount, umounts[i]);
if (mount(umounts[i], newmount, NULL, MS_MOVE, NULL) < 0) {
fprintf(stderr, "Error mount moving old %s %s %m\n",
umounts[i], newmount);
fprintf(stderr, "Forcing unmount of %s\n", umounts[i]);
umount2(umounts[i], MNT_FORCE);
}
}
if (chdir(newroot) < 0) {
errnum=errno;
fprintf(stderr, "switchroot: chdir failed: %m\n");
errno=errnum;
return -1;
}
recursiveRemove("/");
if (mount(newroot, "/", NULL, MS_MOVE, NULL) < 0) {
errnum = errno;
fprintf(stderr, "switchroot: mount failed: %m\n");
errno = errnum;
return -1;
}
if (chroot(".")) {
errnum = errno;
fprintf(stderr, "switchroot: chroot failed: %m\n");
errno = errnum;
return -2;
}
return 1;
}
static void usage(FILE *output)
{
fprintf(output, "usage: switchroot <newrootdir> <init> <args to init>\n");
if (output == stderr)
exit(err_usage);
exit(ok);
}
int main(int argc, char *argv[])
{
char *newroot = argv[1];
char *init = argv[2];
char **initargs = &argv[2];
if (newroot == NULL || newroot[0] == '\0' ||
init == NULL || init[0] == '\0' ) {
usage(stderr);
}
if (switchroot(newroot) < 0) {
fprintf(stderr, "switchroot has failed. Sorry.\n");
return 1;
}
if (access(initargs[0], X_OK))
fprintf(stderr, "WARNING: can't access %s\n", initargs[0]);
/* get session leader */
setsid();
/* set controlling terminal */
ioctl (0, TIOCSCTTY, 1);
execv(initargs[0], initargs);
}
|
