/*
* 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>
*/
#define _GNU_SOURCE 1
#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
#ifndef MNT_DETACH
#define MNT_DETACH 0x2
#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);
}
/*
* vim:noet:ts=8:sw=8:sts=8
*/
