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git.ipfire.org Git - thirdparty/systemd.git/blob - src/core/machine-id-setup.c
1 /* SPDX-License-Identifier: LGPL-2.1+ */
3 This file is part of systemd.
5 Copyright 2010 Lennart Poettering
7 systemd is free software; you can redistribute it and/or modify it
8 under the terms of the GNU Lesser General Public License as published by
9 the Free Software Foundation; either version 2.1 of the License, or
10 (at your option) any later version.
12 systemd is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public License
18 along with systemd; If not, see <http://www.gnu.org/licenses/>.
23 #include <sys/mount.h>
28 #include "alloc-util.h"
31 #include "id128-util.h"
33 #include "machine-id-setup.h"
36 #include "mount-util.h"
37 #include "path-util.h"
38 #include "process-util.h"
39 #include "stat-util.h"
40 #include "string-util.h"
41 #include "umask-util.h"
45 static int generate_machine_id ( const char * root
, sd_id128_t
* ret
) {
46 const char * dbus_machine_id
;
47 _cleanup_close_
int fd
= - 1 ;
52 /* First, try reading the D-Bus machine id, unless it is a symlink */
53 dbus_machine_id
= prefix_roota ( root
, "/var/lib/dbus/machine-id" );
54 fd
= open ( dbus_machine_id
, O_RDONLY
| O_CLOEXEC
| O_NOCTTY
| O_NOFOLLOW
);
56 if ( id128_read_fd ( fd
, ID128_PLAIN
, ret
) >= 0 ) {
57 log_info ( "Initializing machine ID from D-Bus machine ID." );
65 /* If that didn't work, see if we are running in a container,
66 * and a machine ID was passed in via $container_uuid the way
67 * libvirt/LXC does it */
69 if ( detect_container () > 0 ) {
70 _cleanup_free_
char * e
= NULL
;
72 if ( getenv_for_pid ( 1 , "container_uuid" , & e
) > 0 &&
73 sd_id128_from_string ( e
, ret
) >= 0 ) {
74 log_info ( "Initializing machine ID from container UUID." );
78 } else if ( detect_vm () == VIRTUALIZATION_KVM
) {
80 /* If we are not running in a container, see if we are
81 * running in qemu/kvm and a machine ID was passed in
82 * via -uuid on the qemu/kvm command line */
84 if ( id128_read ( "/sys/class/dmi/id/product_uuid" , ID128_UUID
, ret
) >= 0 ) {
85 log_info ( "Initializing machine ID from KVM UUID." );
91 /* If that didn't work, generate a random machine id */
92 r
= sd_id128_randomize ( ret
);
94 return log_error_errno ( r
, "Failed to generate randomized : %m" );
96 log_info ( "Initializing machine ID from random generator." );
100 int machine_id_setup ( const char * root
, sd_id128_t machine_id
, sd_id128_t
* ret
) {
101 const char * etc_machine_id
, * run_machine_id
;
102 _cleanup_close_
int fd
= - 1 ;
106 etc_machine_id
= prefix_roota ( root
, "/etc/machine-id" );
108 RUN_WITH_UMASK ( 0000 ) {
109 /* We create this 0444, to indicate that this isn't really
110 * something you should ever modify. Of course, since the file
111 * will be owned by root it doesn't matter much, but maybe
114 ( void ) mkdir_parents ( etc_machine_id
, 0755 );
115 fd
= open ( etc_machine_id
, O_RDWR
| O_CREAT
| O_CLOEXEC
| O_NOCTTY
, 0444 );
117 int old_errno
= errno
;
119 fd
= open ( etc_machine_id
, O_RDONLY
| O_CLOEXEC
| O_NOCTTY
);
121 if ( old_errno
== EROFS
&& errno
== ENOENT
)
122 log_error_errno ( errno
,
123 "System cannot boot: Missing /etc/machine-id and /etc is mounted read-only. \n "
124 "Booting up is supported only when: \n "
125 "1) /etc/machine-id exists and is populated. \n "
126 "2) /etc/machine-id exists and is empty. \n "
127 "3) /etc/machine-id is missing and /etc is writable. \n " );
129 log_error_errno ( errno
, "Cannot open %s: %m" , etc_machine_id
);
139 /* A we got a valid machine ID argument, that's what counts */
140 if ( sd_id128_is_null ( machine_id
)) {
142 /* Try to read any existing machine ID */
143 if ( id128_read_fd ( fd
, ID128_PLAIN
, ret
) >= 0 )
146 /* Hmm, so, the id currently stored is not useful, then let's generate one */
147 r
= generate_machine_id ( root
, & machine_id
);
153 if ( lseek ( fd
, 0 , SEEK_SET
) == ( off_t
) - 1 )
154 return log_error_errno ( errno
, "Failed to seek %s: %m" , etc_machine_id
);
156 if ( ftruncate ( fd
, 0 ) < 0 )
157 return log_error_errno ( errno
, "Failed to truncate %s: %m" , etc_machine_id
);
159 if ( id128_write_fd ( fd
, ID128_PLAIN
, machine_id
, true ) >= 0 )
165 /* Hmm, we couldn't write it? So let's write it to /run/machine-id as a replacement */
167 run_machine_id
= prefix_roota ( root
, "/run/machine-id" );
170 r
= id128_write ( run_machine_id
, ID128_PLAIN
, machine_id
, false );
172 ( void ) unlink ( run_machine_id
);
173 return log_error_errno ( r
, "Cannot write %s: %m" , run_machine_id
);
176 /* And now, let's mount it over */
177 if ( mount ( run_machine_id
, etc_machine_id
, NULL
, MS_BIND
, NULL
) < 0 ) {
178 ( void ) unlink_noerrno ( run_machine_id
);
179 return log_error_errno ( errno
, "Failed to mount %s: %m" , etc_machine_id
);
182 log_info ( "Installed transient %s file." , etc_machine_id
);
184 /* Mark the mount read-only */
185 if ( mount ( NULL
, etc_machine_id
, NULL
, MS_BIND
| MS_RDONLY
| MS_REMOUNT
, NULL
) < 0 )
186 log_warning_errno ( errno
, "Failed to make transient %s read-only, ignoring: %m" , etc_machine_id
);
195 int machine_id_commit ( const char * root
) {
196 _cleanup_close_
int fd
= - 1 , initial_mntns_fd
= - 1 ;
197 const char * etc_machine_id
;
201 /* Replaces a tmpfs bind mount of /etc/machine-id by a proper file, atomically. For this, the umount is removed
202 * in a mount namespace, a new file is created at the right place. Afterwards the mount is also removed in the
203 * original mount namespace, thus revealing the file that was just created. */
205 etc_machine_id
= prefix_roota ( root
, "/etc/machine-id" );
207 r
= path_is_mount_point ( etc_machine_id
, NULL
, 0 );
209 return log_error_errno ( r
, "Failed to determine whether %s is a mount point: %m" , etc_machine_id
);
211 log_debug ( "%s is not a mount point. Nothing to do." , etc_machine_id
);
215 /* Read existing machine-id */
216 fd
= open ( etc_machine_id
, O_RDONLY
| O_CLOEXEC
| O_NOCTTY
);
218 return log_error_errno ( errno
, "Cannot open %s: %m" , etc_machine_id
);
220 r
= fd_is_temporary_fs ( fd
);
222 return log_error_errno ( r
, "Failed to determine whether %s is on a temporary file system: %m" , etc_machine_id
);
224 log_error ( "%s is not on a temporary file system." , etc_machine_id
);
228 r
= id128_read_fd ( fd
, ID128_PLAIN
, & id
);
230 return log_error_errno ( r
, "We didn't find a valid machine ID in %s." , etc_machine_id
);
234 /* Store current mount namespace */
235 r
= namespace_open ( 0 , NULL
, & initial_mntns_fd
, NULL
, NULL
, NULL
);
237 return log_error_errno ( r
, "Can't fetch current mount namespace: %m" );
239 /* Switch to a new mount namespace, isolate ourself and unmount etc_machine_id in our new namespace */
240 if ( unshare ( CLONE_NEWNS
) < 0 )
241 return log_error_errno ( errno
, "Failed to enter new namespace: %m" );
243 if ( mount ( NULL
, "/" , NULL
, MS_SLAVE
| MS_REC
, NULL
) < 0 )
244 return log_error_errno ( errno
, "Couldn't make-rslave / mountpoint in our private namespace: %m" );
246 if ( umount ( etc_machine_id
) < 0 )
247 return log_error_errno ( errno
, "Failed to unmount transient %s file in our private namespace: %m" , etc_machine_id
);
249 /* Update a persistent version of etc_machine_id */
250 r
= id128_write ( etc_machine_id
, ID128_PLAIN
, id
, true );
252 return log_error_errno ( r
, "Cannot write %s. This is mandatory to get a persistent machine ID: %m" , etc_machine_id
);
254 /* Return to initial namespace and proceed a lazy tmpfs unmount */
255 r
= namespace_enter (- 1 , initial_mntns_fd
, - 1 , - 1 , - 1 );
257 return log_warning_errno ( r
, "Failed to switch back to initial mount namespace: %m. \n We'll keep transient %s file until next reboot." , etc_machine_id
);
259 if ( umount2 ( etc_machine_id
, MNT_DETACH
) < 0 )
260 return log_warning_errno ( errno
, "Failed to unmount transient %s file: %m. \n We keep that mount until next reboot." , etc_machine_id
);