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/>.
28 #include <sys/mount.h>
30 #include "systemd/sd-id128.h"
32 #include "machine-id-setup.h"
39 #include "path-util.h"
41 static int shorten_uuid(char destination[34], const char source[36]) {
44 for (i = 0, j = 0; i < 36 && j < 32; i++) {
47 t = unhexchar(source[i]);
51 destination[j++] = hexchar(t);
54 if (i == 36 && j == 32) {
55 destination[32] = '\n';
63 static int generate(char id[34], const char *root) {
69 const char *vm_id, *dbus_machine_id;
74 dbus_machine_id = "/var/lib/dbus/machine-id";
76 dbus_machine_id = strappenda(root, "/var/lib/dbus/machine-id");
78 /* First, try reading the D-Bus machine id, unless it is a symlink */
79 fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
81 k = loop_read(fd, id, 33, false);
84 if (k == 33 && id[32] == '\n') {
87 if (id128_is_valid(id)) {
91 log_info("Initializing machine ID from D-Bus machine ID.");
98 /* If that didn't work, see if we are running in a container,
99 * and a machine ID was passed in via $container_uuid the way
100 * libvirt/LXC does it */
101 r = detect_container(NULL);
103 _cleanup_free_ char *e = NULL;
105 r = getenv_for_pid(1, "container_uuid", &e);
107 if (strlen(e) >= 36) {
108 r = shorten_uuid(id, e);
110 log_info("Initializing machine ID from container UUID.");
117 /* If we are not running in a container, see if we are
118 * running in qemu/kvm and a machine ID was passed in
119 * via -uuid on the qemu/kvm command line */
121 r = detect_vm(&vm_id);
122 if (r > 0 && streq(vm_id, "kvm")) {
125 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
127 k = loop_read(fd, uuid, 36, false);
131 r = shorten_uuid(id, uuid);
133 log_info("Initializing machine ID from KVM UUID.");
142 /* If that didn't work, generate a random machine id */
143 r = sd_id128_randomize(&buf);
145 log_error("Failed to open /dev/urandom: %s", strerror(-r));
149 for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
150 q[0] = hexchar(*p >> 4);
151 q[1] = hexchar(*p & 15);
157 log_info("Initializing machine ID from random generator.");
162 int machine_id_setup(const char *root) {
163 const char *etc_machine_id, *run_machine_id;
164 _cleanup_close_ int fd = -1;
165 bool writable = true;
167 char id[34]; /* 32 + \n + \0 */
171 etc_machine_id = "/etc/machine-id";
172 run_machine_id = "/run/machine-id";
174 etc_machine_id = strappenda(root, "/etc/machine-id");
175 path_kill_slashes((char*) etc_machine_id);
177 run_machine_id = strappenda(root, "/run/machine-id");
178 path_kill_slashes((char*) run_machine_id);
181 RUN_WITH_UMASK(0000) {
182 /* We create this 0444, to indicate that this isn't really
183 * something you should ever modify. Of course, since the file
184 * will be owned by root it doesn't matter much, but maybe
187 mkdir_parents(etc_machine_id, 0755);
188 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
190 int old_errno = errno;
192 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
194 if (old_errno == EROFS && errno == ENOENT)
195 log_error("System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
196 "Booting up is supported only when:\n"
197 "1) /etc/machine-id exists and is populated.\n"
198 "2) /etc/machine-id exists and is empty.\n"
199 "3) /etc/machine-id is missing and /etc is writable.\n");
201 log_error("Cannot open %s: %m", etc_machine_id);
209 if (fstat(fd, &st) < 0) {
210 log_error("fstat() failed: %m");
214 if (S_ISREG(st.st_mode))
215 if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') {
218 if (id128_is_valid(id))
222 /* Hmm, so, the id currently stored is not useful, then let's
225 r = generate(id, root);
229 if (S_ISREG(st.st_mode) && writable) {
230 lseek(fd, 0, SEEK_SET);
232 if (loop_write(fd, id, 33, false) == 33)
238 /* Hmm, we couldn't write it? So let's write it to
239 * /run/machine-id as a replacement */
241 RUN_WITH_UMASK(0022) {
242 r = write_string_file(run_machine_id, id);
245 log_error("Cannot write %s: %s", run_machine_id, strerror(-r));
246 unlink(run_machine_id);
250 /* And now, let's mount it over */
251 r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
253 log_error("Failed to mount %s: %m", etc_machine_id);
254 unlink_noerrno(run_machine_id);
258 log_info("Installed transient %s file.", etc_machine_id);
260 /* Mark the mount read-only */
261 if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
262 log_warning("Failed to make transient %s read-only: %m", etc_machine_id);