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 General Public License as published by
10 the Free Software Foundation; either version 2 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 General Public License for more details.
18 You should have received a copy of the GNU 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"
38 static int shorten_uuid(char destination[36], const char *source) {
41 for (i = 0, j = 0; i < 36 && j < 32; i++) {
44 t = unhexchar(source[i]);
48 destination[j++] = hexchar(t);
51 if (i == 36 && j == 32) {
52 destination[32] = '\n';
60 static int generate(char id[34]) {
70 /* First, try reading the D-Bus machine id, unless it is a symlink */
71 fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
74 k = loop_read(fd, id, 32, false);
75 close_nointr_nofail(fd);
81 log_info("Initializing machine ID from D-Bus machine ID.");
86 /* If that didn't work, see if we are running in qemu/kvm and a
87 * machine ID was passed in via -uuid on the qemu/kvm command
90 r = detect_vm(&vm_id);
91 if (r > 0 && streq(vm_id, "kvm")) {
94 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
96 k = loop_read(fd, uuid, 36, false);
97 close_nointr_nofail(fd);
100 r = shorten_uuid(id, uuid);
102 log_info("Initializing machine ID from KVM UUID");
109 /* If that didn't work either, see if we are running in a
110 * container, and a machine ID was passed in via
111 * $container_uuid the way libvirt/LXC does it */
113 r = detect_container(NULL);
117 f = fopen("/proc/1/environ", "re");
125 for (i = 0; i < sizeof(line)-1; i++) {
129 if (_unlikely_(c == EOF)) {
139 if (startswith(line, "container_uuid=") &&
140 strlen(line + 15) >= 36) {
141 r = shorten_uuid(id, line + 15);
143 log_info("Initializing machine ID from container UUID");
154 /* If that didn't work, generate a random machine id */
155 r = sd_id128_randomize(&buf);
157 log_error("Failed to open /dev/urandom: %s", strerror(-r));
161 for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
162 q[0] = hexchar(*p >> 4);
163 q[1] = hexchar(*p & 15);
169 log_info("Initializing machine ID from random generator.");
174 int machine_id_setup(void) {
178 char id[34]; /* 32 + \n + \0 */
183 /* We create this 0444, to indicate that this isn't really
184 * something you should ever modify. Of course, since the file
185 * will be owned by root it doesn't matter much, but maybe
188 fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
192 fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
195 log_error("Cannot open /etc/machine-id: %m");
204 if (fstat(fd, &st) < 0) {
205 log_error("fstat() failed: %m");
210 if (S_ISREG(st.st_mode)) {
211 if (loop_read(fd, id, 32, false) >= 32) {
217 /* Hmm, so, the id currently stored is not useful, then let's
224 if (S_ISREG(st.st_mode) && writable) {
225 lseek(fd, 0, SEEK_SET);
227 if (loop_write(fd, id, 33, false) == 33) {
233 close_nointr_nofail(fd);
236 /* Hmm, we couldn't write it? So let's write it to
237 * /run/systemd/machine-id as a replacement */
239 mkdir_p("/run/systemd", 0755);
242 r = write_one_line_file("/run/systemd/machine-id", id);
246 log_error("Cannot write /run/systemd/machine-id: %s", strerror(-r));
248 unlink("/run/systemd/machine-id");
252 /* And now, let's mount it over */
253 r = mount("/run/systemd/machine-id", "/etc/machine-id", "bind", MS_BIND|MS_RDONLY, NULL) < 0 ? -errno : 0;
254 unlink("/run/systemd/machine-id");
257 log_error("Failed to mount /etc/machine-id: %s", strerror(-r));
259 log_info("Installed transient /etc/machine-id file.");
264 close_nointr_nofail(fd);