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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <sys/mount.h>
#include "alloc-util.h"
#include "blockdev-util.h"
#include "escape.h"
#include "fs-util.h"
#include "main-func.h"
#include "mkdir.h"
#include "mount-util.h"
#include "mountpoint-util.h"
#include "path-util.h"
#include "stat-util.h"
#include "string-util.h"
#include "volatile-util.h"
static int make_volatile(const char *path) {
_cleanup_free_ char *old_usr = NULL;
int r;
assert(path);
r = chase_symlinks("/usr", path, CHASE_PREFIX_ROOT, &old_usr, NULL);
if (r < 0)
return log_error_errno(r, "/usr not available in old root: %m");
r = mkdir_p("/run/systemd/volatile-sysroot", 0700);
if (r < 0)
return log_error_errno(r, "Couldn't generate volatile sysroot directory: %m");
r = mount_nofollow_verbose(LOG_ERR, "tmpfs", "/run/systemd/volatile-sysroot", "tmpfs", MS_STRICTATIME, "mode=755" TMPFS_LIMITS_ROOTFS);
if (r < 0)
goto finish_rmdir;
if (mkdir("/run/systemd/volatile-sysroot/usr", 0755) < 0) {
r = log_error_errno(errno, "Failed to create /usr directory: %m");
goto finish_umount;
}
r = mount_nofollow_verbose(LOG_ERR, old_usr, "/run/systemd/volatile-sysroot/usr", NULL, MS_BIND|MS_REC, NULL);
if (r < 0)
goto finish_umount;
r = bind_remount_recursive("/run/systemd/volatile-sysroot/usr", MS_RDONLY, MS_RDONLY, NULL);
if (r < 0) {
log_error_errno(r, "Failed to remount /usr read-only: %m");
goto finish_umount;
}
r = umount_recursive(path, 0);
if (r < 0) {
log_error_errno(r, "Failed to unmount %s: %m", path);
goto finish_umount;
}
if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0)
log_warning_errno(errno, "Failed to remount %s MS_SLAVE|MS_REC, ignoring: %m", path);
r = mount_nofollow_verbose(LOG_ERR, "/run/systemd/volatile-sysroot", path, NULL, MS_MOVE, NULL);
finish_umount:
(void) umount_recursive("/run/systemd/volatile-sysroot", 0);
finish_rmdir:
(void) rmdir("/run/systemd/volatile-sysroot");
return r;
}
static int make_overlay(const char *path) {
_cleanup_free_ char *escaped_path = NULL;
bool tmpfs_mounted = false;
const char *options = NULL;
int r;
assert(path);
r = mkdir_p("/run/systemd/overlay-sysroot", 0700);
if (r < 0)
return log_error_errno(r, "Couldn't create overlay sysroot directory: %m");
r = mount_nofollow_verbose(LOG_ERR, "tmpfs", "/run/systemd/overlay-sysroot", "tmpfs", MS_STRICTATIME, "mode=755" TMPFS_LIMITS_ROOTFS);
if (r < 0)
goto finish;
tmpfs_mounted = true;
if (mkdir("/run/systemd/overlay-sysroot/upper", 0755) < 0) {
r = log_error_errno(errno, "Failed to create /run/systemd/overlay-sysroot/upper: %m");
goto finish;
}
if (mkdir("/run/systemd/overlay-sysroot/work", 0755) < 0) {
r = log_error_errno(errno, "Failed to create /run/systemd/overlay-sysroot/work: %m");
goto finish;
}
escaped_path = shell_escape(path, ",:");
if (!escaped_path) {
r = log_oom();
goto finish;
}
options = strjoina("lowerdir=", escaped_path, ",upperdir=/run/systemd/overlay-sysroot/upper,workdir=/run/systemd/overlay-sysroot/work");
r = mount_nofollow_verbose(LOG_ERR, "overlay", path, "overlay", 0, options);
finish:
if (tmpfs_mounted)
(void) umount_verbose(LOG_ERR, "/run/systemd/overlay-sysroot", UMOUNT_NOFOLLOW);
(void) rmdir("/run/systemd/overlay-sysroot");
return r;
}
static int run(int argc, char *argv[]) {
VolatileMode m = _VOLATILE_MODE_INVALID;
const char *path;
dev_t devt;
int r;
log_setup_service();
if (argc > 3)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Too many arguments. Expected directory and mode.");
r = query_volatile_mode(&m);
if (r < 0)
return log_error_errno(r, "Failed to determine volatile mode from kernel command line.");
if (r == 0 && argc >= 2) {
/* The kernel command line always wins. However if nothing was set there, the argument passed here wins instead. */
m = volatile_mode_from_string(argv[1]);
if (m < 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Couldn't parse volatile mode: %s", argv[1]);
}
if (argc < 3)
path = "/sysroot";
else {
path = argv[2];
if (isempty(path))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Directory name cannot be empty.");
if (!path_is_absolute(path))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Directory must be specified as absolute path.");
if (path_equal(path, "/"))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Directory cannot be the root directory.");
}
if (!IN_SET(m, VOLATILE_YES, VOLATILE_OVERLAY))
return 0;
r = path_is_mount_point(path, NULL, AT_SYMLINK_FOLLOW);
if (r < 0)
return log_error_errno(r, "Couldn't determine whether %s is a mount point: %m", path);
if (r == 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "%s is not a mount point.", path);
r = path_is_temporary_fs(path);
if (r < 0)
return log_error_errno(r, "Couldn't determine whether %s is a temporary file system: %m", path);
if (r > 0) {
log_info("%s already is a temporary file system.", path);
return 0;
}
/* We are about to replace the root directory with something else. Later code might want to know what we
* replaced here, hence let's save that information as a symlink we can later use. (This is particularly
* relevant for the overlayfs case where we'll fully obstruct the view onto the underlying device, hence
* querying the backing device node from the file system directly is no longer possible. */
r = get_block_device_harder(path, &devt);
if (r < 0)
return log_error_errno(r, "Failed to determine device major/minor of %s: %m", path);
else if (r > 0) { /* backed by block device */
_cleanup_free_ char *dn = NULL;
r = device_path_make_major_minor(S_IFBLK, devt, &dn);
if (r < 0)
return log_error_errno(r, "Failed to format device node path: %m");
if (symlink(dn, "/run/systemd/volatile-root") < 0)
log_warning_errno(errno, "Failed to create symlink /run/systemd/volatile-root: %m");
}
if (m == VOLATILE_YES)
return make_volatile(path);
else {
assert(m == VOLATILE_OVERLAY);
return make_overlay(path);
}
}
DEFINE_MAIN_FUNCTION(run);
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