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 int generate(char id[34]) {
43 /* First, try reading the D-Bus machine id, unless it is a symlink */
44 if ((fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW)) >= 0) {
46 k = loop_read(fd, id, 33, false);
47 close_nointr_nofail(fd);
53 log_info("Initializing machine ID from D-Bus machine ID.");
58 /* If that didn't work, generate a random machine id */
59 if ((fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
60 log_error("Failed to open /dev/urandom: %m");
64 k = loop_read(fd, buf, sizeof(buf), false);
65 close_nointr_nofail(fd);
67 if (k != sizeof(buf)) {
68 log_error("Failed to read /dev/urandom: %s", strerror(k < 0 ? -k : EIO));
69 return k < 0 ? (int) k : -EIO;
72 for (p = buf, q = id; p < buf + sizeof(buf); p++, q += 2) {
73 q[0] = hexchar(*p >> 4);
74 q[1] = hexchar(*p & 15);
80 log_info("Initializing machine ID from random generator.");
85 int machine_id_setup(void) {
89 char id[34]; /* 32 + \n + \0 */
94 /* We create this 0444, to indicate that this isn't really
95 * something you should ever modify. Of course, since the file
96 * will be owned by root it doesn't matter much, but maybe
99 if ((fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444)) >= 0)
102 if ((fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
104 log_error("Cannot open /etc/machine-id: %m");
113 if (fstat(fd, &st) < 0) {
114 log_error("fstat() failed: %m");
119 if (S_ISREG(st.st_mode)) {
120 if (loop_read(fd, id, 32, false) >= 32) {
126 /* Hmm, so, the id currently stored is not useful, then let's
129 if ((r = generate(id)) < 0)
132 if (S_ISREG(st.st_mode) && writable) {
133 lseek(fd, 0, SEEK_SET);
135 if (loop_write(fd, id, 33, false) == 33) {
141 close_nointr_nofail(fd);
144 /* Hmm, we couldn't write it? So let's write it to
145 * /run/systemd/machine-id as a replacement */
147 mkdir_p("/run/systemd", 0755);
149 if ((r = write_one_line_file("/run/systemd/machine-id", id)) < 0) {
150 log_error("Cannot write /run/systemd/machine-id: %s", strerror(-r));
152 unlink("/run/systemd/machine-id");
156 /* And now, let's mount it over */
157 r = mount("/run/systemd/machine-id", "/etc/machine-id", "bind", MS_BIND|MS_RDONLY, NULL) < 0 ? -errno : 0;
158 unlink("/run/systemd/machine-id");
161 log_error("Failed to mount /etc/machine-id: %s", strerror(-r));
163 log_info("Installed transient /etc/machine-id file.");
168 close_nointr_nofail(fd);