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"
39 #include "path-util.h"
41 static int shorten_uuid(char destination[36], const char *source) {
44 for (i = 0, j = 0; i < 36 && j < 32; i++) {
47 t = unhexchar(source[i]);
51 destination[j++] = hexchar(t);
54 if (i == 36 && j == 32) {
55 destination[32] = '\n';
63 static int generate(char id[34], const char *root) {
70 _cleanup_free_ char *dbus_machine_id = NULL;
74 if (asprintf(&dbus_machine_id, "%s/var/lib/dbus/machine-id", root) < 0)
77 /* First, try reading the D-Bus machine id, unless it is a symlink */
78 fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
80 k = loop_read(fd, id, 33, false);
83 if (k == 33 && id[32] == '\n') {
86 if (id128_is_valid(id)) {
90 log_info("Initializing machine ID from D-Bus machine ID.");
96 /* If that didn't work, see if we are running in qemu/kvm and a
97 * machine ID was passed in via -uuid on the qemu/kvm command
100 r = detect_vm(&vm_id);
101 if (r > 0 && streq(vm_id, "kvm")) {
104 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
106 k = loop_read(fd, uuid, 36, false);
110 r = shorten_uuid(id, uuid);
112 log_info("Initializing machine ID from KVM UUID.");
119 /* If that didn't work either, see if we are running in a
120 * container, and a machine ID was passed in via
121 * $container_uuid the way libvirt/LXC does it */
122 r = detect_container(NULL);
124 _cleanup_free_ char *e = NULL;
126 r = getenv_for_pid(1, "container_uuid", &e);
128 if (strlen(e) >= 36) {
129 r = shorten_uuid(id, e);
131 log_info("Initializing machine ID from container UUID.");
138 /* If that didn't work, generate a random machine id */
139 r = sd_id128_randomize(&buf);
141 log_error("Failed to open /dev/urandom: %s", strerror(-r));
145 for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
146 q[0] = hexchar(*p >> 4);
147 q[1] = hexchar(*p & 15);
153 log_info("Initializing machine ID from random generator.");
158 int machine_id_setup(const char *root) {
159 _cleanup_close_ int fd = -1;
161 bool writable = false;
163 char id[34]; /* 32 + \n + \0 */
164 char *etc_machine_id, *run_machine_id;
166 etc_machine_id = strappenda(root, "/etc/machine-id");
167 path_kill_slashes(etc_machine_id);
169 run_machine_id = strappenda(root, "/run/machine-id");
170 path_kill_slashes(run_machine_id);
172 RUN_WITH_UMASK(0000) {
173 /* We create this 0444, to indicate that this isn't really
174 * something you should ever modify. Of course, since the file
175 * will be owned by root it doesn't matter much, but maybe
178 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
182 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
184 log_error("Cannot open %s: %m", etc_machine_id);
192 if (fstat(fd, &st) < 0) {
193 log_error("fstat() failed: %m");
197 if (S_ISREG(st.st_mode))
198 if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') {
201 if (id128_is_valid(id))
205 /* Hmm, so, the id currently stored is not useful, then let's
208 r = generate(id, root);
212 if (S_ISREG(st.st_mode) && writable) {
213 lseek(fd, 0, SEEK_SET);
215 if (loop_write(fd, id, 33, false) == 33)
221 /* Hmm, we couldn't write it? So let's write it to
222 * /run/machine-id as a replacement */
224 RUN_WITH_UMASK(0022) {
225 r = write_string_file(run_machine_id, id);
228 log_error("Cannot write %s: %s", run_machine_id, strerror(-r));
229 unlink(run_machine_id);
233 /* And now, let's mount it over */
234 r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
236 log_error("Failed to mount %s: %m", etc_machine_id);
237 unlink_noerrno(run_machine_id);
241 log_info("Installed transient %s file.", etc_machine_id);
243 /* Mark the mount read-only */
244 if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
245 log_warning("Failed to make transient %s read-only: %m", etc_machine_id);