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[34], const char source[36]) {
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 a container,
97 * and a machine ID was passed in via $container_uuid the way
98 * libvirt/LXC does it */
99 r = detect_container(NULL);
101 _cleanup_free_ char *e = NULL;
103 r = getenv_for_pid(1, "container_uuid", &e);
105 if (strlen(e) >= 36) {
106 r = shorten_uuid(id, e);
108 log_info("Initializing machine ID from container UUID.");
115 /* If we are not running in a container, see if we are
116 * running in qemu/kvm and a machine ID was passed in
117 * via -uuid on the qemu/kvm command line */
119 r = detect_vm(&vm_id);
120 if (r > 0 && streq(vm_id, "kvm")) {
123 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
125 k = loop_read(fd, uuid, 36, false);
129 r = shorten_uuid(id, uuid);
131 log_info("Initializing machine ID from KVM UUID.");
139 /* If that didn't work, generate a random machine id */
140 r = sd_id128_randomize(&buf);
142 log_error("Failed to open /dev/urandom: %s", strerror(-r));
146 for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
147 q[0] = hexchar(*p >> 4);
148 q[1] = hexchar(*p & 15);
154 log_info("Initializing machine ID from random generator.");
159 int machine_id_setup(const char *root) {
160 const char *etc_machine_id, *run_machine_id;
161 _cleanup_close_ int fd = -1;
162 bool writable = false;
164 char id[34]; /* 32 + \n + \0 */
168 etc_machine_id = "/etc/machine-id";
169 run_machine_id = "/run/machine-id";
171 etc_machine_id = strappenda(root, "/etc/machine-id");
172 path_kill_slashes((char*) etc_machine_id);
174 run_machine_id = strappenda(root, "/run/machine-id");
175 path_kill_slashes((char*) run_machine_id);
178 RUN_WITH_UMASK(0000) {
179 /* We create this 0444, to indicate that this isn't really
180 * something you should ever modify. Of course, since the file
181 * will be owned by root it doesn't matter much, but maybe
184 mkdir_parents(etc_machine_id, 0755);
185 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
189 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
191 log_error("Cannot open %s: %m", etc_machine_id);
199 if (fstat(fd, &st) < 0) {
200 log_error("fstat() failed: %m");
204 if (S_ISREG(st.st_mode))
205 if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') {
208 if (id128_is_valid(id))
212 /* Hmm, so, the id currently stored is not useful, then let's
215 r = generate(id, root);
219 if (S_ISREG(st.st_mode) && writable) {
220 lseek(fd, 0, SEEK_SET);
222 if (loop_write(fd, id, 33, false) == 33)
228 /* Hmm, we couldn't write it? So let's write it to
229 * /run/machine-id as a replacement */
231 RUN_WITH_UMASK(0022) {
232 r = write_string_file(run_machine_id, id);
235 log_error("Cannot write %s: %s", run_machine_id, strerror(-r));
236 unlink(run_machine_id);
240 /* And now, let's mount it over */
241 r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
243 log_error("Failed to mount %s: %m", etc_machine_id);
244 unlink_noerrno(run_machine_id);
248 log_info("Installed transient %s file.", etc_machine_id);
250 /* Mark the mount read-only */
251 if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
252 log_warning("Failed to make transient %s read-only: %m", etc_machine_id);