diff options
Diffstat (limited to '')
| -rw-r--r-- | src/volatile-root/volatile-root.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/src/volatile-root/volatile-root.c b/src/volatile-root/volatile-root.c new file mode 100644 index 0000000..e29d4df --- /dev/null +++ b/src/volatile-root/volatile-root.c @@ -0,0 +1,197 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <sys/mount.h> + +#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); |