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) {
70 _cleanup_free_ char *dbus_machine_id = NULL;
74 if (asprintf(&dbus_machine_id, "%s/var/lib/dbus/machine-id", root) < 0)
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.");
96 /* If that didn't work, see if we are running in a container,
97 * and a machine ID was passed in via $container_uuid the way
98 * libvirt/LXC does it */
99 r = detect_container(NULL);
101 _cleanup_free_ char *e = NULL;
103 r = getenv_for_pid(1, "container_uuid", &e);
105 if (strlen(e) >= 36) {
106 r = shorten_uuid(id, e);
108 log_info("Initializing machine ID from container UUID.");
115 /* If we are not running in a container, see if we are
116 * running in qemu/kvm and a machine ID was passed in
117 * via -uuid on the qemu/kvm command line */
119 r = detect_vm(&vm_id);
120 if (r > 0 && streq(vm_id, "kvm")) {
123 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
125 k = loop_read(fd, uuid, 36, false);
129 r = shorten_uuid(id, uuid);
131 log_info("Initializing machine ID from KVM UUID.");
139 /* If that didn't work, generate a random machine id */
140 r = sd_id128_randomize(&buf);
142 log_error("Failed to open /dev/urandom: %s", strerror(-r));
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 int machine_id_setup(const char *root) {
160 _cleanup_close_ int fd = -1;
162 bool writable = false;
164 char id[34]; /* 32 + \n + \0 */
165 char *etc_machine_id, *run_machine_id;
167 etc_machine_id = strappenda(root, "/etc/machine-id");
168 path_kill_slashes(etc_machine_id);
170 run_machine_id = strappenda(root, "/run/machine-id");
171 path_kill_slashes(run_machine_id);
173 RUN_WITH_UMASK(0000) {
174 /* We create this 0444, to indicate that this isn't really
175 * something you should ever modify. Of course, since the file
176 * will be owned by root it doesn't matter much, but maybe
179 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
183 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
185 log_error("Cannot open %s: %m", etc_machine_id);
193 if (fstat(fd, &st) < 0) {
194 log_error("fstat() failed: %m");
198 if (S_ISREG(st.st_mode))
199 if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') {
202 if (id128_is_valid(id))
206 /* Hmm, so, the id currently stored is not useful, then let's
209 r = generate(id, root);
213 if (S_ISREG(st.st_mode) && writable) {
214 lseek(fd, 0, SEEK_SET);
216 if (loop_write(fd, id, 33, false) == 33)
222 /* Hmm, we couldn't write it? So let's write it to
223 * /run/machine-id as a replacement */
225 RUN_WITH_UMASK(0022) {
226 r = write_string_file(run_machine_id, id);
229 log_error("Cannot write %s: %s", run_machine_id, strerror(-r));
230 unlink(run_machine_id);
234 /* And now, let's mount it over */
235 r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
237 log_error("Failed to mount %s: %m", etc_machine_id);
238 unlink_noerrno(run_machine_id);
242 log_info("Installed transient %s file.", etc_machine_id);
244 /* Mark the mount read-only */
245 if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
246 log_warning("Failed to make transient %s read-only: %m", etc_machine_id);