/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include "alloc-util.h" #include "blockdev-util.h" #include "chase-symlinks.h" #include "devnum-util.h" #include "escape.h" #include "main-func.h" #include "mkdir.h" #include "mount-util.h" #include "mountpoint-util.h" #include "path-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(); 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: %m"); 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(m, "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);