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]) {
43 for (i = 0, j = 0; i < 36 && j < 32; i++) {
46 t = unhexchar(source[i]);
50 destination[j++] = hexchar(t);
53 if (i == 36 && j == 32) {
54 destination[32] = '\n';
62 static int generate(char id[34], const char *root) {
68 const char *vm_id, *dbus_machine_id;
73 dbus_machine_id = "/var/lib/dbus/machine-id";
75 dbus_machine_id = strjoina(root, "/var/lib/dbus/machine-id");
77 /* First, try reading the D-Bus machine id, unless it is a symlink */
78 fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
80 k = loop_read(fd, id, 33, false);
83 if (k == 33 && id[32] == '\n') {
86 if (id128_is_valid(id)) {
90 log_info("Initializing machine ID from D-Bus machine ID.");
97 /* If that didn't work, see if we are running in a container,
98 * and a machine ID was passed in via $container_uuid the way
99 * libvirt/LXC does it */
100 r = detect_container(NULL);
102 _cleanup_free_ char *e = NULL;
104 r = getenv_for_pid(1, "container_uuid", &e);
106 if (strlen(e) >= 36) {
107 r = shorten_uuid(id, e);
109 log_info("Initializing machine ID from container UUID.");
116 /* If we are not running in a container, see if we are
117 * running in qemu/kvm and a machine ID was passed in
118 * via -uuid on the qemu/kvm command line */
120 r = detect_vm(&vm_id);
121 if (r > 0 && streq(vm_id, "kvm")) {
124 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
126 k = loop_read(fd, uuid, 36, false);
130 r = shorten_uuid(id, uuid);
132 log_info("Initializing machine ID from KVM UUID.");
141 /* If that didn't work, generate a random machine id */
142 r = sd_id128_randomize(&buf);
144 return log_error_errno(r, "Failed to open /dev/urandom: %m");
146 for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
147 q[0] = hexchar(*p >> 4);
148 q[1] = hexchar(*p & 15);
154 log_info("Initializing machine ID from random generator.");
159 static int get_valid_machine_id(int fd, char id[34]) {
160 char id_to_validate[34];
165 if (loop_read(fd, id_to_validate, 33, false) == 33 && id_to_validate[32] == '\n') {
166 id_to_validate[32] = 0;
168 if (id128_is_valid(id_to_validate)) {
169 memcpy(id, id_to_validate, 32);
179 static int write_machine_id(int fd, char id[34]) {
182 lseek(fd, 0, SEEK_SET);
184 if (loop_write(fd, id, 33, false) == 0)
190 int machine_id_commit(const char *root) {
191 _cleanup_close_ int fd = -1, initial_mntns_fd = -1;
192 const char *etc_machine_id;
193 char id[34]; /* 32 + \n + \0 */
197 etc_machine_id = "/etc/machine-id";
201 x = strjoina(root, "/etc/machine-id");
202 etc_machine_id = path_kill_slashes(x);
205 r = path_is_mount_point(etc_machine_id, false);
207 return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", etc_machine_id);
209 log_debug("%s is is not a mount point. Nothing to do.", etc_machine_id);
213 /* Read existing machine-id */
214 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
216 return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
218 r = get_valid_machine_id(fd, id);
220 return log_error_errno(r, "We didn't find a valid machine ID in %s.", etc_machine_id);
222 r = is_fd_on_temporary_fs(fd);
224 return log_error_errno(r, "Failed to determine whether %s is on a temporary file system: %m", etc_machine_id);
226 log_error("%s is not on a temporary file system.", etc_machine_id);
232 /* Store current mount namespace */
233 r = namespace_open(0, NULL, &initial_mntns_fd, NULL, NULL);
235 return log_error_errno(r, "Can't fetch current mount namespace: %m");
237 /* Switch to a new mount namespace, isolate ourself and unmount etc_machine_id in our new namespace */
238 if (unshare(CLONE_NEWNS) < 0)
239 return log_error_errno(errno, "Failed to enter new namespace: %m");
241 if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) < 0)
242 return log_error_errno(errno, "Couldn't make-rslave / mountpoint in our private namespace: %m");
244 if (umount(etc_machine_id) < 0)
245 return log_error_errno(errno, "Failed to unmount transient %s file in our private namespace: %m", etc_machine_id);
247 /* Update a persistent version of etc_machine_id */
248 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
250 return log_error_errno(errno, "Cannot open for writing %s. This is mandatory to get a persistent machine-id: %m", etc_machine_id);
252 r = write_machine_id(fd, id);
254 return log_error_errno(r, "Cannot write %s: %m", etc_machine_id);
258 /* Return to initial namespace and proceed a lazy tmpfs unmount */
259 r = namespace_enter(-1, initial_mntns_fd, -1, -1);
261 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);
263 if (umount2(etc_machine_id, MNT_DETACH) < 0)
264 return log_warning_errno(errno, "Failed to unmount transient %s file: %m.\nWe keep that mount until next reboot.", etc_machine_id);
269 int machine_id_setup(const char *root) {
270 const char *etc_machine_id, *run_machine_id;
271 _cleanup_close_ int fd = -1;
272 bool writable = true;
274 char id[34]; /* 32 + \n + \0 */
278 etc_machine_id = "/etc/machine-id";
279 run_machine_id = "/run/machine-id";
283 x = strjoina(root, "/etc/machine-id");
284 etc_machine_id = path_kill_slashes(x);
286 x = strjoina(root, "/run/machine-id");
287 run_machine_id = path_kill_slashes(x);
290 RUN_WITH_UMASK(0000) {
291 /* We create this 0444, to indicate that this isn't really
292 * something you should ever modify. Of course, since the file
293 * will be owned by root it doesn't matter much, but maybe
296 mkdir_parents(etc_machine_id, 0755);
297 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
299 int old_errno = errno;
301 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
303 if (old_errno == EROFS && errno == ENOENT)
304 log_error("System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
305 "Booting up is supported only when:\n"
306 "1) /etc/machine-id exists and is populated.\n"
307 "2) /etc/machine-id exists and is empty.\n"
308 "3) /etc/machine-id is missing and /etc is writable.\n");
310 log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
318 if (fstat(fd, &st) < 0)
319 return log_error_errno(errno, "fstat() failed: %m");
321 if (S_ISREG(st.st_mode) && get_valid_machine_id(fd, id) == 0)
324 /* Hmm, so, the id currently stored is not useful, then let's
327 r = generate(id, root);
331 if (S_ISREG(st.st_mode) && writable)
332 if (write_machine_id(fd, id) == 0)
337 /* Hmm, we couldn't write it? So let's write it to
338 * /run/machine-id as a replacement */
340 RUN_WITH_UMASK(0022) {
341 r = write_string_file(run_machine_id, id);
344 log_error_errno(r, "Cannot write %s: %m", run_machine_id);
345 unlink(run_machine_id);
349 /* And now, let's mount it over */
350 r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
352 log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
353 unlink_noerrno(run_machine_id);
357 log_info("Installed transient %s file.", etc_machine_id);
359 /* Mark the mount read-only */
360 if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
361 log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);