dracut: New package.
[people/pmueller/ipfire-2.x.git] / src / dracut / switch_root.c
1 /*
2 * switchroot.c - switch to new root directory and start init.
3 *
4 * Copyright 2002-2008 Red Hat, Inc. All rights reserved.
5 *
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.
10 *
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.
15 *
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/>.
18 *
19 * Authors:
20 * Peter Jones <pjones@redhat.com>
21 * Jeremy Katz <katzj@redhat.com>
22 */
23 #include <sys/mount.h>
24 #include <sys/types.h>
25 #include <sys/stat.h>
26 #include <sys/param.h>
27 #include <fcntl.h>
28 #include <stdio.h>
29 #include <stdlib.h>
30 #include <unistd.h>
31 #include <string.h>
32 #include <errno.h>
33 #include <ctype.h>
34 #include <dirent.h>
35
36 #ifndef MS_MOVE
37 #define MS_MOVE 8192
38 #endif
39
40 enum {
41 ok,
42 err_no_directory,
43 err_usage,
44 };
45
46 /* remove all files/directories below dirName -- don't cross mountpoints */
47 static int
48 recursiveRemove(char * dirName)
49 {
50 struct stat sb,rb;
51 DIR * dir;
52 struct dirent * d;
53 char * strBuf = alloca(strlen(dirName) + 1024);
54
55 if (!(dir = opendir(dirName))) {
56 printf("error opening %s: %m\n", dirName);
57 return 0;
58 }
59
60 if (fstat(dirfd(dir),&rb)) {
61 printf("unable to stat %s: %m\n", dirName);
62 closedir(dir);
63 return 0;
64 }
65
66 errno = 0;
67
68 while ((d = readdir(dir))) {
69 errno = 0;
70
71 if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, "..")) {
72 errno = 0;
73 continue;
74 }
75
76 strcpy(strBuf, dirName);
77 strcat(strBuf, "/");
78 strcat(strBuf, d->d_name);
79
80 if (lstat(strBuf, &sb)) {
81 printf("failed to stat %s: %m\n", strBuf);
82 errno = 0;
83 continue;
84 }
85
86 /* only descend into subdirectories if device is same as dir */
87 if (S_ISDIR(sb.st_mode)) {
88 if (sb.st_dev == rb.st_dev) {
89 recursiveRemove(strBuf);
90 if (rmdir(strBuf))
91 printf("failed to rmdir %s: %m\n", strBuf);
92 }
93 errno = 0;
94 continue;
95 }
96 if (unlink(strBuf)) {
97 printf("failed to remove %s: %m\n", strBuf);
98 errno = 0;
99 continue;
100 }
101 }
102
103 if (errno) {
104 closedir(dir);
105 printf("error reading from %s: %m\n", dirName);
106 return 1;
107 }
108
109 closedir(dir);
110 return 0;
111 }
112
113 static int switchroot(const char *newroot)
114 {
115 /* Don't try to unmount the old "/", there's no way to do it. */
116 const char *umounts[] = { "/dev", "/proc", "/sys", NULL };
117 int errnum;
118 int i;
119
120 for (i = 0; umounts[i] != NULL; i++) {
121 char newmount[PATH_MAX];
122 strcpy(newmount, newroot);
123 strcat(newmount, umounts[i]);
124 if (mount(umounts[i], newmount, NULL, MS_MOVE, NULL) < 0) {
125 fprintf(stderr, "Error mount moving old %s %s %m\n",
126 umounts[i], newmount);
127 fprintf(stderr, "Forcing unmount of %s\n", umounts[i]);
128 umount2(umounts[i], MNT_FORCE);
129 }
130 }
131
132 if (chdir(newroot) < 0) {
133 errnum=errno;
134 fprintf(stderr, "switchroot: chdir failed: %m\n");
135 errno=errnum;
136 return -1;
137 }
138 recursiveRemove("/");
139 if (mount(newroot, "/", NULL, MS_MOVE, NULL) < 0) {
140 errnum = errno;
141 fprintf(stderr, "switchroot: mount failed: %m\n");
142 errno = errnum;
143 return -1;
144 }
145
146 if (chroot(".")) {
147 errnum = errno;
148 fprintf(stderr, "switchroot: chroot failed: %m\n");
149 errno = errnum;
150 return -2;
151 }
152 return 1;
153 }
154
155 static void usage(FILE *output)
156 {
157 fprintf(output, "usage: switchroot <newrootdir> <init> <args to init>\n");
158 if (output == stderr)
159 exit(err_usage);
160 exit(ok);
161 }
162
163 int main(int argc, char *argv[])
164 {
165 char *newroot = argv[1];
166 char *init = argv[2];
167 char **initargs = &argv[2];
168
169 if (newroot == NULL || newroot[0] == '\0' ||
170 init == NULL || init[0] == '\0' ) {
171 usage(stderr);
172 }
173
174 if (switchroot(newroot) < 0) {
175 fprintf(stderr, "switchroot has failed. Sorry.\n");
176 return 1;
177 }
178 if (access(initargs[0], X_OK))
179 fprintf(stderr, "WARNING: can't access %s\n", initargs[0]);
180
181 /* get session leader */
182 setsid();
183 /* set controlling terminal */
184 ioctl (0, TIOCSCTTY, 1);
185
186 execv(initargs[0], initargs);
187 }
188