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 static int get_valid_machine_id(int fd, char id[34]) {
161 char id_to_validate[34];
166 if (loop_read(fd, id_to_validate, 33, false) == 33 && id_to_validate[32] == '\n') {
167 id_to_validate[32] = 0;
169 if (id128_is_valid(id_to_validate)) {
170 memcpy(id, id_to_validate, 32);
180 static int write_machine_id(int fd, char id[34]) {
183 lseek(fd, 0, SEEK_SET);
185 if (loop_write(fd, id, 33, false) == 33)
191 int machine_id_setup(const char *root) {
192 const char *etc_machine_id, *run_machine_id;
193 _cleanup_close_ int fd = -1;
194 bool writable = true;
196 char id[34]; /* 32 + \n + \0 */
200 etc_machine_id = "/etc/machine-id";
201 run_machine_id = "/run/machine-id";
203 etc_machine_id = strappenda(root, "/etc/machine-id");
204 path_kill_slashes((char*) etc_machine_id);
206 run_machine_id = strappenda(root, "/run/machine-id");
207 path_kill_slashes((char*) run_machine_id);
210 RUN_WITH_UMASK(0000) {
211 /* We create this 0444, to indicate that this isn't really
212 * something you should ever modify. Of course, since the file
213 * will be owned by root it doesn't matter much, but maybe
216 mkdir_parents(etc_machine_id, 0755);
217 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
219 int old_errno = errno;
221 fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
223 if (old_errno == EROFS && errno == ENOENT)
224 log_error("System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
225 "Booting up is supported only when:\n"
226 "1) /etc/machine-id exists and is populated.\n"
227 "2) /etc/machine-id exists and is empty.\n"
228 "3) /etc/machine-id is missing and /etc is writable.\n");
230 log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
238 if (fstat(fd, &st) < 0)
239 return log_error_errno(errno, "fstat() failed: %m");
241 if (S_ISREG(st.st_mode) && get_valid_machine_id(fd, id) == 0)
244 /* Hmm, so, the id currently stored is not useful, then let's
247 r = generate(id, root);
251 if (S_ISREG(st.st_mode) && writable) {
252 if (write_machine_id(fd, id) == 0)
258 /* Hmm, we couldn't write it? So let's write it to
259 * /run/machine-id as a replacement */
261 RUN_WITH_UMASK(0022) {
262 r = write_string_file(run_machine_id, id);
265 log_error_errno(r, "Cannot write %s: %m", run_machine_id);
266 unlink(run_machine_id);
270 /* And now, let's mount it over */
271 r = mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);
273 log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
274 unlink_noerrno(run_machine_id);
278 log_info("Installed transient %s file.", etc_machine_id);
280 /* Mark the mount read-only */
281 if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
282 log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);