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"
40 static int shorten_uuid(char destination[36], const char *source) {
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]) {
72 /* First, try reading the D-Bus machine id, unless it is a symlink */
73 fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
76 k = loop_read(fd, id, 32, false);
77 close_nointr_nofail(fd);
83 log_info("Initializing machine ID from D-Bus machine ID.");
88 /* If that didn't work, see if we are running in qemu/kvm and a
89 * machine ID was passed in via -uuid on the qemu/kvm command
92 r = detect_vm(&vm_id);
93 if (r > 0 && streq(vm_id, "kvm")) {
96 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
98 k = loop_read(fd, uuid, 36, false);
99 close_nointr_nofail(fd);
102 r = shorten_uuid(id, uuid);
104 log_info("Initializing machine ID from KVM UUID.");
111 /* If that didn't work either, see if we are running in a
112 * container, and a machine ID was passed in via
113 * $container_uuid the way libvirt/LXC does it */
114 r = detect_container(NULL);
118 r = getenv_for_pid(1, "container_uuid", &e);
120 if (strlen(e) >= 36) {
121 r = shorten_uuid(id, e);
123 log_info("Initializing machine ID from container UUID.");
133 /* If that didn't work, generate a random machine id */
134 r = sd_id128_randomize(&buf);
136 log_error("Failed to open /dev/urandom: %s", strerror(-r));
140 for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
141 q[0] = hexchar(*p >> 4);
142 q[1] = hexchar(*p & 15);
148 log_info("Initializing machine ID from random generator.");
153 int machine_id_setup(void) {
157 char id[34]; /* 32 + \n + \0 */
162 /* We create this 0444, to indicate that this isn't really
163 * something you should ever modify. Of course, since the file
164 * will be owned by root it doesn't matter much, but maybe
167 fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
171 fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
174 log_error("Cannot open /etc/machine-id: %m");
183 if (fstat(fd, &st) < 0) {
184 log_error("fstat() failed: %m");
189 if (S_ISREG(st.st_mode)) {
190 if (loop_read(fd, id, 32, false) >= 32) {
196 /* Hmm, so, the id currently stored is not useful, then let's
203 if (S_ISREG(st.st_mode) && writable) {
204 lseek(fd, 0, SEEK_SET);
206 if (loop_write(fd, id, 33, false) == 33) {
212 close_nointr_nofail(fd);
215 /* Hmm, we couldn't write it? So let's write it to
216 * /run/machine-id as a replacement */
219 r = write_one_line_file("/run/machine-id", id);
223 log_error("Cannot write /run/machine-id: %s", strerror(-r));
225 unlink("/run/machine-id");
229 /* And now, let's mount it over */
230 r = mount("/run/machine-id", "/etc/machine-id", NULL, MS_BIND, NULL) < 0 ? -errno : 0;
232 unlink("/run/machine-id");
233 log_error("Failed to mount /etc/machine-id: %s", strerror(-r));
235 log_info("Installed transient /etc/machine-id file.");
237 /* Mark the mount read-only */
238 mount(NULL, "/etc/machine-id", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL);
244 close_nointr_nofail(fd);