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) {
69 const char *vm_id, *dbus_machine_id;
74 dbus_machine_id = "/var/lib/dbus/machine-id";
76 dbus_machine_id = strappenda(root, "/var/lib/dbus/machine-id");
78 /* First, try reading the D-Bus machine id, unless it is a symlink */
79 fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
81 k = loop_read(fd, id, 33, false);
84 if (k == 33 && id[32] == '\n') {
87 if (id128_is_valid(id)) {
91 log_info("Initializing machine ID from D-Bus machine ID.");
98 /* If that didn't work, see if we are running in a container,
99 * and a machine ID was passed in via $container_uuid the way
100 * libvirt/LXC does it */
101 r = detect_container(NULL);
103 _cleanup_free_ char *e = NULL;
105 r = getenv_for_pid(1, "container_uuid", &e);
107 if (strlen(e) >= 36) {
108 r = shorten_uuid(id, e);
110 log_info("Initializing machine ID from container UUID.");
117 /* If we are not running in a container, see if we are
118 * running in qemu/kvm and a machine ID was passed in
119 * via -uuid on the qemu/kvm command line */
121 r = detect_vm(&vm_id);
122 if (r > 0 && streq(vm_id, "kvm")) {
125 fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
127 k = loop_read(fd, uuid, 36, false);
131 r = shorten_uuid(id, uuid);
133 log_info("Initializing machine ID from KVM UUID.");
142 /* If that didn't work, generate a random machine id */
143 r = sd_id128_randomize(&buf);
145 return log_error_errno(r, "Failed to open /dev/urandom: %m");
147 for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
148 q[0] = hexchar(*p >> 4);
149 q[1] = hexchar(*p & 15);
155 log_info("Initializing machine ID from random generator.");
160 int machine_id_setup(const char *root) {
161 const char *etc_machine_id, *run_machine_id;
162 _cleanup_close_ int fd = -1;
163 bool writable = true;
165 char id[34]; /* 32 + \n + \0 */
169 etc_machine_id = "/etc/machine-id";
170 run_machine_id = "/run/machine-id";
172 etc_machine_id = strappenda(root, "/etc/machine-id");
173 path_kill_slashes((char*) etc_machine_id);
175 run_machine_id = strappenda(root, "/run/machine-id");
176 path_kill_slashes((char*) run_machine_id);
179 RUN_WITH_UMASK(0000) {
180 /* We create this 0444, to indicate that this isn't really
181 * something you should ever modify. Of course, since the file
182 * will be owned by root it doesn't matter much, but maybe
185 mkdir_parents(etc_machine_id, 0755);
186 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
188 int old_errno = errno;
190 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
192 if (old_errno == EROFS && errno == ENOENT)
193 log_error("System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
194 "Booting up is supported only when:\n"
195 "1) /etc/machine-id exists and is populated.\n"
196 "2) /etc/machine-id exists and is empty.\n"
197 "3) /etc/machine-id is missing and /etc is writable.\n");
199 log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
207 if (fstat(fd, &st) < 0)
208 return log_error_errno(errno, "fstat() failed: %m");
210 if (S_ISREG(st.st_mode))
211 if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') {
214 if (id128_is_valid(id))
218 /* Hmm, so, the id currently stored is not useful, then let's
221 r = generate(id, root);
225 if (S_ISREG(st.st_mode) && writable) {
226 lseek(fd, 0, SEEK_SET);
228 if (loop_write(fd, id, 33, false) == 33)
234 /* Hmm, we couldn't write it? So let's write it to
235 * /run/machine-id as a replacement */
237 RUN_WITH_UMASK(0022) {
238 r = write_string_file(run_machine_id, id);
241 log_error_errno(r, "Cannot write %s: %m", run_machine_id);
242 unlink(run_machine_id);
246 /* And now, let's mount it over */
247 r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
249 log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
250 unlink_noerrno(run_machine_id);
254 log_info("Installed transient %s file.", etc_machine_id);
256 /* Mark the mount read-only */
257 if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
258 log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);