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Diffstat (limited to '')
| -rw-r--r-- | sys-utils/switch_root.c | 263 |
1 files changed, 263 insertions, 0 deletions
diff --git a/sys-utils/switch_root.c b/sys-utils/switch_root.c new file mode 100644 index 0000000..a85ce24 --- /dev/null +++ b/sys-utils/switch_root.c @@ -0,0 +1,263 @@ +/* + * switchroot.c - switch to new root directory and start init. + * + * Copyright 2002-2009 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/statfs.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> +#include <getopt.h> + +#include "c.h" +#include "nls.h" +#include "closestream.h" +#include "statfs_magic.h" + +#ifndef MS_MOVE +#define MS_MOVE 8192 +#endif + +#ifndef MNT_DETACH +#define MNT_DETACH 0x00000002 /* Just detach from the tree */ +#endif + +/* remove all files/directories below dirName -- don't cross mountpoints */ +static int recursiveRemove(int fd) +{ + struct stat rb; + DIR *dir; + int rc = -1; + int dfd; + + if (!(dir = fdopendir(fd))) { + warn(_("failed to open directory")); + goto done; + } + + /* fdopendir() precludes us from continuing to use the input fd */ + dfd = dirfd(dir); + + if (fstat(dfd, &rb)) { + warn(_("stat failed")); + goto done; + } + + while(1) { + struct dirent *d; + int isdir = 0; + + errno = 0; + if (!(d = readdir(dir))) { + if (errno) { + warn(_("failed to read directory")); + goto done; + } + break; /* end of directory */ + } + + if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, "..")) + continue; +#ifdef _DIRENT_HAVE_D_TYPE + if (d->d_type == DT_DIR || d->d_type == DT_UNKNOWN) +#endif + { + struct stat sb; + + if (fstatat(dfd, d->d_name, &sb, AT_SYMLINK_NOFOLLOW)) { + warn(_("stat of %s failed"), d->d_name); + continue; + } + + /* skip if device is not the same */ + if (sb.st_dev != rb.st_dev) + continue; + + /* remove subdirectories */ + if (S_ISDIR(sb.st_mode)) { + int cfd; + + cfd = openat(dfd, d->d_name, O_RDONLY); + if (cfd >= 0) { + recursiveRemove(cfd); + close(cfd); + } + isdir = 1; + } + } + + if (unlinkat(dfd, d->d_name, isdir ? AT_REMOVEDIR : 0)) + warn(_("failed to unlink %s"), d->d_name); + } + + rc = 0; /* success */ + +done: + if (dir) + closedir(dir); + return rc; +} + +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", "/run", NULL }; + int i; + int cfd; + pid_t pid; + struct stat newroot_stat, sb; + + if (stat(newroot, &newroot_stat) != 0) { + warn(_("stat of %s failed"), newroot); + return -1; + } + + for (i = 0; umounts[i] != NULL; i++) { + char newmount[PATH_MAX]; + + snprintf(newmount, sizeof(newmount), "%s%s", newroot, umounts[i]); + + if ((stat(newmount, &sb) != 0) || (sb.st_dev != newroot_stat.st_dev)) { + /* mount point seems to be mounted already or stat failed */ + umount2(umounts[i], MNT_DETACH); + continue; + } + + if (mount(umounts[i], newmount, NULL, MS_MOVE, NULL) < 0) { + warn(_("failed to mount moving %s to %s"), + umounts[i], newmount); + warnx(_("forcing unmount of %s"), umounts[i]); + umount2(umounts[i], MNT_FORCE); + } + } + + if (chdir(newroot)) { + warn(_("failed to change directory to %s"), newroot); + return -1; + } + + cfd = open("/", O_RDONLY); + if (cfd < 0) { + warn(_("cannot open %s"), "/"); + return -1; + } + + if (mount(newroot, "/", NULL, MS_MOVE, NULL) < 0) { + close(cfd); + warn(_("failed to mount moving %s to /"), newroot); + return -1; + } + + if (chroot(".")) { + close(cfd); + warn(_("failed to change root")); + return -1; + } + + pid = fork(); + if (pid <= 0) { + struct statfs stfs; + + if (fstatfs(cfd, &stfs) == 0 && + (F_TYPE_EQUAL(stfs.f_type, STATFS_RAMFS_MAGIC) || + F_TYPE_EQUAL(stfs.f_type, STATFS_TMPFS_MAGIC))) + recursiveRemove(cfd); + else + warn(_("old root filesystem is not an initramfs")); + if (pid == 0) + exit(EXIT_SUCCESS); + } + + close(cfd); + return 0; +} + +static void __attribute__((__noreturn__)) usage(void) +{ + FILE *output = stdout; + fputs(USAGE_HEADER, output); + fprintf(output, _(" %s [options] <newrootdir> <init> <args to init>\n"), + program_invocation_short_name); + + fputs(USAGE_SEPARATOR, output); + fputs(_("Switch to another filesystem as the root of the mount tree.\n"), output); + + fputs(USAGE_OPTIONS, output); + printf(USAGE_HELP_OPTIONS(16)); + printf(USAGE_MAN_TAIL("switch_root(8)")); + + exit(EXIT_SUCCESS); +} + +int main(int argc, char *argv[]) +{ + char *newroot, *init, **initargs; + int c; + static const struct option longopts[] = { + {"version", no_argument, NULL, 'V'}, + {"help", no_argument, NULL, 'h'}, + {NULL, 0, NULL, 0} + }; + + atexit(close_stdout); + + while ((c = getopt_long(argc, argv, "+Vh", longopts, NULL)) != -1) + switch (c) { + case 'V': + printf(UTIL_LINUX_VERSION); + return EXIT_SUCCESS; + case 'h': + usage(); + default: + errtryhelp(EXIT_FAILURE); + } + if (argc < 3) { + warnx(_("not enough arguments")); + errtryhelp(EXIT_FAILURE); + } + + newroot = argv[1]; + init = argv[2]; + initargs = &argv[2]; + + if (!*newroot || !*init) { + warnx(_("bad usage")); + errtryhelp(EXIT_FAILURE); + } + + if (switchroot(newroot)) + errx(EXIT_FAILURE, _("failed. Sorry.")); + + if (access(init, X_OK)) + warn(_("cannot access %s"), init); + + execv(init, initargs); + errexec(init); +} + |