+++ /dev/null
-/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
-
-/***
- This file is part of systemd.
-
- Copyright 2012 Harald Hoyer, Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd 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
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
-***/
-
-#include <sys/stat.h>
-#include <stdbool.h>
-#include <errno.h>
-#include <string.h>
-#include <sys/mount.h>
-#include <unistd.h>
-#include <fcntl.h>
-
-#include "util.h"
-#include "path-util.h"
-#include "switch-root.h"
-#include "mkdir.h"
-#include "base-filesystem.h"
-#include "missing.h"
-
-int switch_root(const char *new_root) {
-
- /* Don't try to unmount/move the old "/", there's no way to do it. */
- static const char move_mounts[] =
- "/dev\0"
- "/proc\0"
- "/sys\0"
- "/run\0";
-
- _cleanup_close_ int old_root_fd = -1;
- struct stat new_root_stat;
- bool old_root_remove;
- const char *i, *temporary_old_root;
- int r;
-
- if (path_equal(new_root, "/"))
- return 0;
-
- /* When using pivot_root() we assume that /mnt exists as place
- * we can temporarily move the old root to. As we immediately
- * unmount it from there it doesn't matter much which
- * directory we choose for this, but it should be more likely
- * than not that /mnt exists and is suitable as mount point
- * and is on the same fs as the old root dir */
- temporary_old_root = strappenda(new_root, "/mnt");
- mkdir_p(temporary_old_root, 0755);
-
- old_root_remove = in_initrd();
-
- if (stat(new_root, &new_root_stat) < 0) {
- log_error("Failed to stat directory %s: %m", new_root);
- return -errno;
- }
-
- /* Work-around for a kernel bug: for some reason the kernel
- * refuses switching root if any file systems are mounted
- * MS_SHARED. Hence remount them MS_PRIVATE here as a
- * work-around.
- *
- * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */
- if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0)
- log_warning("Failed to make \"/\" private mount: %m");
-
- NULSTR_FOREACH(i, move_mounts) {
- char new_mount[PATH_MAX];
- struct stat sb;
-
- snprintf(new_mount, sizeof(new_mount), "%s%s", new_root, i);
- char_array_0(new_mount);
-
- mkdir_p(new_mount, 0755);
-
- if ((stat(new_mount, &sb) < 0) ||
- sb.st_dev != new_root_stat.st_dev) {
-
- /* Mount point seems to be mounted already or
- * stat failed. Unmount the old mount
- * point. */
- if (umount2(i, MNT_DETACH) < 0)
- log_warning("Failed to unmount %s: %m", i);
- continue;
- }
-
- if (mount(i, new_mount, NULL, MS_MOVE, NULL) < 0) {
- log_error("Failed to move mount %s to %s, forcing unmount: %m", i, new_mount);
-
- if (umount2(i, MNT_FORCE) < 0)
- log_warning("Failed to unmount %s: %m", i);
- }
- }
-
- r = base_filesystem_create(new_root);
- if (r < 0) {
- log_error("Failed to create the base filesystem: %s", strerror(-r));
- return r;
- }
-
- if (chdir(new_root) < 0) {
- log_error("Failed to change directory to %s: %m", new_root);
- return -errno;
- }
-
- if (old_root_remove) {
- old_root_fd = open("/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY|O_DIRECTORY);
- if (old_root_fd < 0)
- log_warning("Failed to open root directory: %m");
- }
-
- /* We first try a pivot_root() so that we can umount the old
- * root dir. In many cases (i.e. where rootfs is /), that's
- * not possible however, and hence we simply overmount root */
- if (pivot_root(new_root, temporary_old_root) >= 0) {
-
- /* Immediately get rid of the old root. Since we are
- * running off it we need to do this lazily. */
- if (umount2("/mnt", MNT_DETACH) < 0) {
- log_error("Failed to umount old root dir /mnt: %m");
- return -errno;
- }
-
- } else if (mount(new_root, "/", NULL, MS_MOVE, NULL) < 0) {
- log_error("Failed to mount moving %s to /: %m", new_root);
- return -errno;
- }
-
- if (chroot(".") < 0) {
- log_error("Failed to change root: %m");
- return -errno;
- }
-
- if (chdir("/") < 0) {
- log_error("Failed to change directory: %m");
- return -errno;
- }
-
- if (old_root_fd >= 0) {
- struct stat rb;
-
- if (fstat(old_root_fd, &rb) < 0)
- log_warning("Failed to stat old root directory, leaving: %m");
- else {
- rm_rf_children(old_root_fd, false, false, &rb);
- old_root_fd = -1;
- }
- }
-
- return 0;
-}
~ianmdlvl / elogind.git / blobdiff