1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
4 This file is part of systemd.
6 Copyright 2010 Lennart Poettering
8 systemd is free software; you can redistribute it and/or modify it
9 under the terms of the GNU Lesser General Public License as published by
10 the Free Software Foundation; either version 2.1 of the License, or
11 (at your option) any later version.
13 systemd is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 Lesser General Public License for more details.
18 You should have received a copy of the GNU Lesser General Public License
19 along with systemd; If not, see <http://www.gnu.org/licenses/>.
27 #include <sys/mount.h>
29 #include "systemd/sd-id128.h"
31 #include "machine-id-setup.h"
38 #include "path-util.h"
40 static int shorten_uuid(char destination[34], const char source[36]) {
46 /* Converts a UUID into a machine ID, by lowercasing it and
47 * removing dashes. Validates everything. */
49 for (i = 0, j = 0; i < 36 && j < 32; i++) {
52 t = unhexchar(source[i]);
56 destination[j++] = hexchar(t);
59 if (i != 36 || j != 32)
62 destination[32] = '\n';
67 static int read_machine_id(int fd, char id[34]) {
68 char id_to_validate[34];
74 /* Reads a machine ID from a file, validates it, and returns
75 * it. The returned ID ends in a newline. */
77 r = loop_read_exact(fd, id_to_validate, 33, false);
81 if (id_to_validate[32] != '\n')
84 id_to_validate[32] = 0;
86 if (!id128_is_valid(id_to_validate))
89 memcpy(id, id_to_validate, 32);
95 static int write_machine_id(int fd, char id[34]) {
99 if (lseek(fd, 0, SEEK_SET) < 0)
102 return loop_write(fd, id, 33, false);
105 static int generate_machine_id(char id[34], const char *root) {
110 const char *vm_id, *dbus_machine_id;
115 dbus_machine_id = "/var/lib/dbus/machine-id";
117 dbus_machine_id = strjoina(root, "/var/lib/dbus/machine-id");
119 /* First, try reading the D-Bus machine id, unless it is a symlink */
120 fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
122 r = read_machine_id(fd, id);
126 log_info("Initializing machine ID from D-Bus machine ID.");
132 /* If that didn't work, see if we are running in a container,
133 * and a machine ID was passed in via $container_uuid the way
134 * libvirt/LXC does it */
135 r = detect_container(NULL);
137 _cleanup_free_ char *e = NULL;
139 r = getenv_for_pid(1, "container_uuid", &e);
141 r = shorten_uuid(id, e);
143 log_info("Initializing machine ID from container UUID.");
149 /* If we are not running in a container, see if we are
150 * running in qemu/kvm and a machine ID was passed in
151 * via -uuid on the qemu/kvm command line */
153 r = detect_vm(&vm_id);
154 if (r > 0 && streq(vm_id, "kvm")) {
157 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
159 r = loop_read_exact(fd, uuid, 36, false);
163 r = shorten_uuid(id, uuid);
165 log_info("Initializing machine ID from KVM UUID.");
174 /* If that didn't work, generate a random machine id */
175 r = sd_id128_randomize(&buf);
177 return log_error_errno(r, "Failed to open /dev/urandom: %m");
179 for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
180 q[0] = hexchar(*p >> 4);
181 q[1] = hexchar(*p & 15);
187 log_info("Initializing machine ID from random generator.");
192 int machine_id_setup(const char *root) {
193 const char *etc_machine_id, *run_machine_id;
194 _cleanup_close_ int fd = -1;
195 bool writable = true;
196 char id[34]; /* 32 + \n + \0 */
200 etc_machine_id = "/etc/machine-id";
201 run_machine_id = "/run/machine-id";
205 x = strjoina(root, "/etc/machine-id");
206 etc_machine_id = path_kill_slashes(x);
208 x = strjoina(root, "/run/machine-id");
209 run_machine_id = path_kill_slashes(x);
212 RUN_WITH_UMASK(0000) {
213 /* We create this 0444, to indicate that this isn't really
214 * something you should ever modify. Of course, since the file
215 * will be owned by root it doesn't matter much, but maybe
218 mkdir_parents(etc_machine_id, 0755);
219 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
221 int old_errno = errno;
223 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
225 if (old_errno == EROFS && errno == ENOENT)
226 log_error_errno(errno,
227 "System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
228 "Booting up is supported only when:\n"
229 "1) /etc/machine-id exists and is populated.\n"
230 "2) /etc/machine-id exists and is empty.\n"
231 "3) /etc/machine-id is missing and /etc is writable.\n");
233 log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
242 if (read_machine_id(fd, id) >= 0)
245 /* Hmm, so, the id currently stored is not useful, then let's
248 r = generate_machine_id(id, root);
253 if (write_machine_id(fd, id) >= 0)
258 /* Hmm, we couldn't write it? So let's write it to
259 * /run/machine-id as a replacement */
261 RUN_WITH_UMASK(0022) {
262 r = write_string_file(run_machine_id, id);
265 (void) unlink(run_machine_id);
266 return log_error_errno(r, "Cannot write %s: %m", run_machine_id);
269 /* And now, let's mount it over */
270 if (mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL) < 0) {
271 (void) unlink_noerrno(run_machine_id);
272 return log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
275 log_info("Installed transient %s file.", etc_machine_id);
277 /* Mark the mount read-only */
278 if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
279 log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);
284 int machine_id_commit(const char *root) {
285 _cleanup_close_ int fd = -1, initial_mntns_fd = -1;
286 const char *etc_machine_id;
287 char id[34]; /* 32 + \n + \0 */
291 etc_machine_id = "/etc/machine-id";
295 x = strjoina(root, "/etc/machine-id");
296 etc_machine_id = path_kill_slashes(x);
299 r = path_is_mount_point(etc_machine_id, false);
301 return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", etc_machine_id);
303 log_debug("%s is is not a mount point. Nothing to do.", etc_machine_id);
307 /* Read existing machine-id */
308 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
310 return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
312 r = read_machine_id(fd, id);
314 return log_error_errno(r, "We didn't find a valid machine ID in %s.", etc_machine_id);
316 r = is_fd_on_temporary_fs(fd);
318 return log_error_errno(r, "Failed to determine whether %s is on a temporary file system: %m", etc_machine_id);
320 log_error("%s is not on a temporary file system.", etc_machine_id);
326 /* Store current mount namespace */
327 r = namespace_open(0, NULL, &initial_mntns_fd, NULL, NULL);
329 return log_error_errno(r, "Can't fetch current mount namespace: %m");
331 /* Switch to a new mount namespace, isolate ourself and unmount etc_machine_id in our new namespace */
332 if (unshare(CLONE_NEWNS) < 0)
333 return log_error_errno(errno, "Failed to enter new namespace: %m");
335 if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) < 0)
336 return log_error_errno(errno, "Couldn't make-rslave / mountpoint in our private namespace: %m");
338 if (umount(etc_machine_id) < 0)
339 return log_error_errno(errno, "Failed to unmount transient %s file in our private namespace: %m", etc_machine_id);
341 /* Update a persistent version of etc_machine_id */
342 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
344 return log_error_errno(errno, "Cannot open for writing %s. This is mandatory to get a persistent machine-id: %m", etc_machine_id);
346 r = write_machine_id(fd, id);
348 return log_error_errno(r, "Cannot write %s: %m", etc_machine_id);
352 /* Return to initial namespace and proceed a lazy tmpfs unmount */
353 r = namespace_enter(-1, initial_mntns_fd, -1, -1);
355 return log_warning_errno(r, "Failed to switch back to initial mount namespace: %m.\nWe'll keep transient %s file until next reboot.", etc_machine_id);
357 if (umount2(etc_machine_id, MNT_DETACH) < 0)
358 return log_warning_errno(errno, "Failed to unmount transient %s file: %m.\nWe keep that mount until next reboot.", etc_machine_id);