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);
75 k = loop_read(fd, id, 33, false);
76 close_nointr_nofail(fd);
78 if (k == 33 && id[32] == '\n') {
81 if (id128_is_valid(id)) {
85 log_info("Initializing machine ID from D-Bus machine ID.");
91 /* If that didn't work, see if we are running in qemu/kvm and a
92 * machine ID was passed in via -uuid on the qemu/kvm command
95 r = detect_vm(&vm_id);
96 if (r > 0 && streq(vm_id, "kvm")) {
99 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
101 k = loop_read(fd, uuid, 36, false);
102 close_nointr_nofail(fd);
105 r = shorten_uuid(id, uuid);
107 log_info("Initializing machine ID from KVM UUID.");
114 /* If that didn't work either, see if we are running in a
115 * container, and a machine ID was passed in via
116 * $container_uuid the way libvirt/LXC does it */
117 r = detect_container(NULL);
119 _cleanup_free_ char *e = NULL;
121 r = getenv_for_pid(1, "container_uuid", &e);
123 if (strlen(e) >= 36) {
124 r = shorten_uuid(id, e);
126 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) {
154 _cleanup_close_ int fd = -1;
156 bool writable = false;
158 char id[34]; /* 32 + \n + \0 */
160 RUN_WITH_UMASK(0000) {
161 /* We create this 0444, to indicate that this isn't really
162 * something you should ever modify. Of course, since the file
163 * will be owned by root it doesn't matter much, but maybe
166 fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
170 fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
172 log_error("Cannot open /etc/machine-id: %m");
180 if (fstat(fd, &st) < 0) {
181 log_error("fstat() failed: %m");
185 if (S_ISREG(st.st_mode))
186 if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') {
189 if (id128_is_valid(id))
193 /* Hmm, so, the id currently stored is not useful, then let's
200 if (S_ISREG(st.st_mode) && writable) {
201 lseek(fd, 0, SEEK_SET);
203 if (loop_write(fd, id, 33, false) == 33)
207 close_nointr_nofail(fd);
210 /* Hmm, we couldn't write it? So let's write it to
211 * /run/machine-id as a replacement */
213 RUN_WITH_UMASK(0022) {
214 r = write_string_file("/run/machine-id", id);
217 log_error("Cannot write /run/machine-id: %s", strerror(-r));
218 unlink("/run/machine-id");
222 /* And now, let's mount it over */
223 r = mount("/run/machine-id", "/etc/machine-id", NULL, MS_BIND, NULL);
225 log_error("Failed to mount /etc/machine-id: %m");
226 unlink_noerrno("/run/machine-id");
230 log_info("Installed transient /etc/machine-id file.");
232 /* Mark the mount read-only */
233 if (mount(NULL, "/etc/machine-id", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
234 log_warning("Failed to make transient /etc/machine-id read-only: %m");