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 "machine-id-setup.h"
35 static void make_v4_uuid(unsigned char *id) {
36 /* Stolen from generate_random_uuid() of drivers/char/random.c
37 * in the kernel sources */
39 /* Set UUID version to 4 --- truly random generation */
40 id[6] = (id[6] & 0x0F) | 0x40;
42 /* Set the UUID variant to DCE */
43 id[8] = (id[8] & 0x3F) | 0x80;
46 static int generate(char id[34]) {
48 unsigned char buf[16], *p;
54 /* First, try reading the D-Bus machine id, unless it is a symlink */
55 fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
58 k = loop_read(fd, id, 33, false);
59 close_nointr_nofail(fd);
65 log_info("Initializing machine ID from D-Bus machine ID.");
70 /* If that didn't work, generate a random machine id */
71 fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
73 log_error("Failed to open /dev/urandom: %m");
77 k = loop_read(fd, buf, sizeof(buf), false);
78 close_nointr_nofail(fd);
80 if (k != sizeof(buf)) {
81 log_error("Failed to read /dev/urandom: %s", strerror(k < 0 ? -k : EIO));
82 return k < 0 ? (int) k : -EIO;
85 /* Turn this into a valid v4 UUID, to be nice. Note that we
86 * only guarantee this for newly generated UUIDs, not for
87 * pre-existing ones.*/
90 for (p = buf, q = id; p < buf + sizeof(buf); p++, q += 2) {
91 q[0] = hexchar(*p >> 4);
92 q[1] = hexchar(*p & 15);
98 log_info("Initializing machine ID from random generator.");
103 int machine_id_setup(void) {
107 char id[34]; /* 32 + \n + \0 */
112 /* We create this 0444, to indicate that this isn't really
113 * something you should ever modify. Of course, since the file
114 * will be owned by root it doesn't matter much, but maybe
117 fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
121 fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
124 log_error("Cannot open /etc/machine-id: %m");
133 if (fstat(fd, &st) < 0) {
134 log_error("fstat() failed: %m");
139 if (S_ISREG(st.st_mode)) {
140 if (loop_read(fd, id, 32, false) >= 32) {
146 /* Hmm, so, the id currently stored is not useful, then let's
153 if (S_ISREG(st.st_mode) && writable) {
154 lseek(fd, 0, SEEK_SET);
156 if (loop_write(fd, id, 33, false) == 33) {
162 close_nointr_nofail(fd);
165 /* Hmm, we couldn't write it? So let's write it to
166 * /run/systemd/machine-id as a replacement */
168 mkdir_p("/run/systemd", 0755);
171 r = write_one_line_file("/run/systemd/machine-id", id);
175 log_error("Cannot write /run/systemd/machine-id: %s", strerror(-r));
177 unlink("/run/systemd/machine-id");
181 /* And now, let's mount it over */
182 r = mount("/run/systemd/machine-id", "/etc/machine-id", "bind", MS_BIND|MS_RDONLY, NULL) < 0 ? -errno : 0;
183 unlink("/run/systemd/machine-id");
186 log_error("Failed to mount /etc/machine-id: %s", strerror(-r));
188 log_info("Installed transient /etc/machine-id file.");
193 close_nointr_nofail(fd);