125 lines
2.9 KiB
C
125 lines
2.9 KiB
C
/*
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* switchroot.c - switch to new root directory and start init.
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*
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* Copyright 2002-2008 Red Hat, Inc. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* Authors:
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* Peter Jones <pjones@redhat.com>
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* Jeremy Katz <katzj@redhat.com>
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*/
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#define _GNU_SOURCE 1
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#include <sys/mount.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/param.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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#include <ctype.h>
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#ifndef MS_MOVE
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#define MS_MOVE 8192
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#endif
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#ifndef MNT_DETACH
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#define MNT_DETACH 0x2
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#endif
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enum {
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ok,
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err_no_directory,
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err_usage,
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};
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static int switchroot(const char *newroot)
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{
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/* Don't try to unmount the old "/", there's no way to do it. */
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const char *umounts[] = { "/dev", "/proc", "/sys", NULL };
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int errnum;
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int i;
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for (i = 0; umounts[i] != NULL; i++) {
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char newmount[PATH_MAX];
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strcpy(newmount, newroot);
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strcat(newmount, umounts[i]);
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if (mount(umounts[i], newmount, NULL, MS_MOVE, NULL) < 0) {
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fprintf(stderr, "Error mount moving old %s %s %m\n",
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umounts[i], newmount);
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fprintf(stderr, "Forcing unmount of %s\n", umounts[i]);
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umount2(umounts[i], MNT_FORCE);
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}
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}
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if (chdir(newroot) < 0) {
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errnum=errno;
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fprintf(stderr, "switchroot: chdir failed: %m\n");
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errno=errnum;
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return -1;
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}
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if (mount(newroot, "/", NULL, MS_MOVE, NULL) < 0) {
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errnum = errno;
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fprintf(stderr, "switchroot: mount failed: %m\n");
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errno = errnum;
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return -1;
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}
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if (chroot(".")) {
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errnum = errno;
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fprintf(stderr, "switchroot: chroot failed: %m\n");
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errno = errnum;
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return -2;
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}
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return 1;
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}
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static void usage(FILE *output)
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{
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fprintf(output, "usage: switchroot <newrootdir> <init> <args to init>\n");
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if (output == stderr)
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exit(err_usage);
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exit(ok);
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}
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int main(int argc, char *argv[])
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{
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char *newroot = argv[1];
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char *init = argv[2];
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char **initargs = &argv[2];
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if (newroot == NULL || newroot[0] == '\0' ||
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init == NULL || init[0] == '\0' ) {
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usage(stderr);
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}
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if (switchroot(newroot) < 0) {
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fprintf(stderr, "switchroot has failed. Sorry.\n");
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return 1;
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}
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if (access(initargs[0], X_OK))
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fprintf(stderr, "WARNING: can't access %s\n", initargs[0]);
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execv(initargs[0], initargs);
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}
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/*
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* vim:noet:ts=8:sw=8:sts=8
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*/
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