[thirdparty/systemd.git] / src / core / machine-id-setup.c

/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <stdio.h>
#include <string.h>
#include <sys/mount.h>
#include <unistd.h>

#include "sd-id128.h"

#include "alloc-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "hexdecoct.h"
#include "io-util.h"
#include "log.h"
#include "machine-id-setup.h"
#include "macro.h"
#include "mkdir.h"
#include "mount-util.h"
#include "path-util.h"
#include "process-util.h"
#include "stat-util.h"
#include "string-util.h"
#include "umask-util.h"
#include "util.h"
#include "virt.h"

static int shorten_uuid(char destination[34], const char source[36]) {
        unsigned i, j;

        assert(destination);
        assert(source);

        /* Converts a UUID into a machine ID, by lowercasing it and
         * removing dashes. Validates everything. */

        for (i = 0, j = 0; i < 36 && j < 32; i++) {
                int t;

                t = unhexchar(source[i]);
                if (t < 0)
                        continue;

                destination[j++] = hexchar(t);
        }

        if (i != 36 || j != 32)
                return -EINVAL;

        destination[32] = '\n';
        destination[33] = 0;
        return 0;
}

static int read_machine_id(int fd, char id[34]) {
        char id_to_validate[34];
        int r;

        assert(fd >= 0);
        assert(id);

        /* Reads a machine ID from a file, validates it, and returns
         * it. The returned ID ends in a newline. */

        r = loop_read_exact(fd, id_to_validate, 33, false);
        if (r < 0)
                return r;

        if (id_to_validate[32] != '\n')
                return -EINVAL;

        id_to_validate[32] = 0;

        if (!id128_is_valid(id_to_validate))
                return -EINVAL;

        memcpy(id, id_to_validate, 32);
        id[32] = '\n';
        id[33] = 0;
        return 0;
}

static int write_machine_id(int fd, char id[34]) {
        assert(fd >= 0);
        assert(id);

        if (lseek(fd, 0, SEEK_SET) < 0)
                return -errno;

        return loop_write(fd, id, 33, false);
}

static int generate_machine_id(char id[34], const char *root) {
        int fd, r;
        unsigned char *p;
        sd_id128_t buf;
        char  *q;
        const char *dbus_machine_id;

        assert(id);

        if (isempty(root))
                dbus_machine_id = "/var/lib/dbus/machine-id";
        else
                dbus_machine_id = strjoina(root, "/var/lib/dbus/machine-id");

        /* First, try reading the D-Bus machine id, unless it is a symlink */
        fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
        if (fd >= 0) {
                r = read_machine_id(fd, id);
                safe_close(fd);

                if (r >= 0) {
                        log_info("Initializing machine ID from D-Bus machine ID.");
                        return 0;
                }
        }

        if (isempty(root)) {
                /* If that didn't work, see if we are running in a container,
                 * and a machine ID was passed in via $container_uuid the way
                 * libvirt/LXC does it */

                if (detect_container() > 0) {
                        _cleanup_free_ char *e = NULL;

                        r = getenv_for_pid(1, "container_uuid", &e);
                        if (r > 0) {
                                r = shorten_uuid(id, e);
                                if (r >= 0) {
                                        log_info("Initializing machine ID from container UUID.");
                                        return 0;
                                }
                        }

                } else if (detect_vm() == VIRTUALIZATION_KVM) {

                        /* If we are not running in a container, see if we are
                         * running in qemu/kvm and a machine ID was passed in
                         * via -uuid on the qemu/kvm command line */

                        char uuid[36];

                        fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
                        if (fd >= 0) {
                                r = loop_read_exact(fd, uuid, 36, false);
                                safe_close(fd);

                                if (r >= 0) {
                                        r = shorten_uuid(id, uuid);
                                        if (r >= 0) {
                                                log_info("Initializing machine ID from KVM UUID.");
                                                return 0;
                                        }
                                }
                        }
                }
        }

        /* If that didn't work, generate a random machine id */
        r = sd_id128_randomize(&buf);
        if (r < 0)
                return log_error_errno(r, "Failed to open /dev/urandom: %m");

        for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
                q[0] = hexchar(*p >> 4);
                q[1] = hexchar(*p & 15);
        }

        id[32] = '\n';
        id[33] = 0;

        log_info("Initializing machine ID from random generator.");

        return 0;
}

int machine_id_setup(const char *root) {
        const char *etc_machine_id, *run_machine_id;
        _cleanup_close_ int fd = -1;
        bool writable = true;
        char id[34]; /* 32 + \n + \0 */
        int r;

        if (isempty(root))  {
                etc_machine_id = "/etc/machine-id";
                run_machine_id = "/run/machine-id";
        } else {
                char *x;

                x = strjoina(root, "/etc/machine-id");
                etc_machine_id = path_kill_slashes(x);

                x = strjoina(root, "/run/machine-id");
                run_machine_id = path_kill_slashes(x);
        }

        RUN_WITH_UMASK(0000) {
                /* We create this 0444, to indicate that this isn't really
                 * something you should ever modify. Of course, since the file
                 * will be owned by root it doesn't matter much, but maybe
                 * people look. */

                mkdir_parents(etc_machine_id, 0755);
                fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
                if (fd < 0) {
                        int old_errno = errno;

                        fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
                        if (fd < 0) {
                                if (old_errno == EROFS && errno == ENOENT)
                                        log_error_errno(errno,
                                                  "System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
                                                  "Booting up is supported only when:\n"
                                                  "1) /etc/machine-id exists and is populated.\n"
                                                  "2) /etc/machine-id exists and is empty.\n"
                                                  "3) /etc/machine-id is missing and /etc is writable.\n");
                                else
                                        log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);

                                return -errno;
                        }

                        writable = false;
                }
        }

        if (read_machine_id(fd, id) >= 0)
                return 0;

        /* Hmm, so, the id currently stored is not useful, then let's
         * generate one */

        r = generate_machine_id(id, root);
        if (r < 0)
                return r;

        if (writable)
                if (write_machine_id(fd, id) >= 0)
                        return 0;

        fd = safe_close(fd);

        /* Hmm, we couldn't write it? So let's write it to
         * /run/machine-id as a replacement */

        RUN_WITH_UMASK(0022) {
                r = write_string_file(run_machine_id, id, WRITE_STRING_FILE_CREATE);
        }
        if (r < 0) {
                (void) unlink(run_machine_id);
                return log_error_errno(r, "Cannot write %s: %m", run_machine_id);
        }

        /* And now, let's mount it over */
        if (mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL) < 0) {
                (void) unlink_noerrno(run_machine_id);
                return log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
        }

        log_info("Installed transient %s file.", etc_machine_id);

        /* Mark the mount read-only */
        if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
                log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);

        return 0;
}

int machine_id_commit(const char *root) {
        _cleanup_close_ int fd = -1, initial_mntns_fd = -1;
        const char *etc_machine_id;
        char id[34]; /* 32 + \n + \0 */
        int r;

        if (isempty(root))
                etc_machine_id = "/etc/machine-id";
        else {
                char *x;

                x = strjoina(root, "/etc/machine-id");
                etc_machine_id = path_kill_slashes(x);
        }

        r = path_is_mount_point(etc_machine_id, 0);
        if (r < 0)
                return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", etc_machine_id);
        if (r == 0) {
                log_debug("%s is is not a mount point. Nothing to do.", etc_machine_id);
                return 0;
        }

        /* Read existing machine-id */
        fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
        if (fd < 0)
                return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);

        r = read_machine_id(fd, id);
        if (r < 0)
                return log_error_errno(r, "We didn't find a valid machine ID in %s.", etc_machine_id);

        r = fd_is_temporary_fs(fd);
        if (r < 0)
                return log_error_errno(r, "Failed to determine whether %s is on a temporary file system: %m", etc_machine_id);
        if (r == 0) {
                log_error("%s is not on a temporary file system.", etc_machine_id);
                return -EROFS;
        }

        fd = safe_close(fd);

        /* Store current mount namespace */
        r = namespace_open(0, NULL, &initial_mntns_fd, NULL, NULL, NULL);
        if (r < 0)
                return log_error_errno(r, "Can't fetch current mount namespace: %m");

        /* Switch to a new mount namespace, isolate ourself and unmount etc_machine_id in our new namespace */
        if (unshare(CLONE_NEWNS) < 0)
                return log_error_errno(errno, "Failed to enter new namespace: %m");

        if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) < 0)
                return log_error_errno(errno, "Couldn't make-rslave / mountpoint in our private namespace: %m");

        if (umount(etc_machine_id) < 0)
                return log_error_errno(errno, "Failed to unmount transient %s file in our private namespace: %m", etc_machine_id);

        /* Update a persistent version of etc_machine_id */
        fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
        if (fd < 0)
                return log_error_errno(errno, "Cannot open for writing %s. This is mandatory to get a persistent machine-id: %m", etc_machine_id);

        r = write_machine_id(fd, id);
        if (r < 0)
                return log_error_errno(r, "Cannot write %s: %m", etc_machine_id);

        fd = safe_close(fd);

        /* Return to initial namespace and proceed a lazy tmpfs unmount */
        r = namespace_enter(-1, initial_mntns_fd, -1, -1, -1);
        if (r < 0)
                return log_warning_errno(r, "Failed to switch back to initial mount namespace: %m.\nWe'll keep transient %s file until next reboot.", etc_machine_id);

        if (umount2(etc_machine_id, MNT_DETACH) < 0)
                return log_warning_errno(errno, "Failed to unmount transient %s file: %m.\nWe keep that mount until next reboot.", etc_machine_id);

        return 0;
}
Commit	Line	Data
d7ccca2e LP	1	/-- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil --/
	2
	3	/***
	4	This file is part of systemd.
	5
	6	Copyright 2010 Lennart Poettering
	7
	8	systemd is free software; you can redistribute it and/or modify it
5430f7f2 LP	9	under the terms of the GNU Lesser General Public License as published by
5430f7f2 LP	10	the Free Software Foundation; either version 2.1 of the License, or
d7ccca2e LP	11	(at your option) any later version.
	12
	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
5430f7f2	16	Lesser General Public License for more details.
d7ccca2e	17
5430f7f2	18	You should have received a copy of the GNU Lesser General Public License
d7ccca2e LP	19	along with systemd; If not, see <http://www.gnu.org/licenses/>.
	20	***/
	21
d7ccca2e	22	#include <errno.h>
d7ccca2e	23	#include <fcntl.h>
618234a5 LP	24	#include <sched.h>
	25	#include <stdio.h>
	26	#include <string.h>
d7ccca2e	27	#include <sys/mount.h>
618234a5	28	#include <unistd.h>
d7ccca2e	29
618234a5	30	#include "sd-id128.h"
81527be1	31
b5efdb8a	32	#include "alloc-util.h"
3ffd4af2	33	#include "fd-util.h"
618234a5	34	#include "fileio.h"
f4f15635	35	#include "fs-util.h"
4349cd7c	36	#include "hexdecoct.h"
c004493c	37	#include "io-util.h"
618234a5	38	#include "log.h"
3ffd4af2	39	#include "machine-id-setup.h"
d7ccca2e	40	#include "macro.h"
49e942b2	41	#include "mkdir.h"
4349cd7c	42	#include "mount-util.h"
fe970a8a	43	#include "path-util.h"
0b452006	44	#include "process-util.h"
8fcde012	45	#include "stat-util.h"
07630cea	46	#include "string-util.h"
affb60b1	47	#include "umask-util.h"
618234a5 LP	48	#include "util.h"
618234a5 LP	49	#include "virt.h"
8d41a963	50
34f750b7	51	static int shorten_uuid(char destination[34], const char source[36]) {
09b967ea LP	52	unsigned i, j;
09b967ea LP	53
c6ac7e4b LP	54	assert(destination);
	55	assert(source);
	56
	57	/* Converts a UUID into a machine ID, by lowercasing it and
	58	* removing dashes. Validates everything. */
	59
09b967ea LP	60	for (i = 0, j = 0; i < 36 && j < 32; i++) {
	61	int t;
	62
	63	t = unhexchar(source[i]);
	64	if (t < 0)
	65	continue;
	66
	67	destination[j++] = hexchar(t);
	68	}
	69
c6ac7e4b LP	70	if (i != 36 \|\| j != 32)
	71	return -EINVAL;
	72
	73	destination[32] = '\n';
	74	destination[33] = 0;
	75	return 0;
	76	}
	77
	78	static int read_machine_id(int fd, char id[34]) {
	79	char id_to_validate[34];
	80	int r;
	81
	82	assert(fd >= 0);
	83	assert(id);
	84
	85	/* Reads a machine ID from a file, validates it, and returns
	86	* it. The returned ID ends in a newline. */
	87
	88	r = loop_read_exact(fd, id_to_validate, 33, false);
	89	if (r < 0)
	90	return r;
	91
	92	if (id_to_validate[32] != '\n')
	93	return -EINVAL;
	94
	95	id_to_validate[32] = 0;
	96
	97	if (!id128_is_valid(id_to_validate))
	98	return -EINVAL;
	99
	100	memcpy(id, id_to_validate, 32);
	101	id[32] = '\n';
	102	id[33] = 0;
	103	return 0;
	104	}
09b967ea	105
c6ac7e4b LP	106	static int write_machine_id(int fd, char id[34]) {
	107	assert(fd >= 0);
	108	assert(id);
	109
	110	if (lseek(fd, 0, SEEK_SET) < 0)
	111	return -errno;
	112
	113	return loop_write(fd, id, 33, false);
09b967ea LP	114	}
09b967ea LP	115
c6ac7e4b	116	static int generate_machine_id(char id[34], const char *root) {
87d2c1ff LP	117	int fd, r;
	118	unsigned char *p;
	119	sd_id128_t buf;
5dd6d0f8	120	char *q;
75f86906	121	const char *dbus_machine_id;
d7ccca2e LP	122
	123	assert(id);
	124
5dd6d0f8 LP	125	if (isempty(root))
	126	dbus_machine_id = "/var/lib/dbus/machine-id";
	127	else
63c372cb	128	dbus_machine_id = strjoina(root, "/var/lib/dbus/machine-id");
92f2f92e	129
d7ccca2e	130	/* First, try reading the D-Bus machine id, unless it is a symlink */
92f2f92e	131	fd = open(dbus_machine_id, O_RDONLY\|O_CLOEXEC\|O_NOCTTY\|O_NOFOLLOW);
8d41a963	132	if (fd >= 0) {
c6ac7e4b	133	r = read_machine_id(fd, id);
03e334a1	134	safe_close(fd);
d7ccca2e	135
c6ac7e4b LP	136	if (r >= 0) {
	137	log_info("Initializing machine ID from D-Bus machine ID.");
	138	return 0;
d7ccca2e LP	139	}
	140	}
	141
5dd6d0f8 LP	142	if (isempty(root)) {
	143	/* If that didn't work, see if we are running in a container,
	144	* and a machine ID was passed in via $container_uuid the way
	145	* libvirt/LXC does it */
75f86906 LP	146
75f86906 LP	147	if (detect_container() > 0) {
5dd6d0f8	148	_cleanup_free_ char *e = NULL;
0b36bbc4	149
5dd6d0f8 LP	150	r = getenv_for_pid(1, "container_uuid", &e);
5dd6d0f8 LP	151	if (r > 0) {
c6ac7e4b LP	152	r = shorten_uuid(id, e);
	153	if (r >= 0) {
	154	log_info("Initializing machine ID from container UUID.");
	155	return 0;
0b36bbc4 LP	156	}
0b36bbc4 LP	157	}
5dd6d0f8	158
75f86906 LP	159	} else if (detect_vm() == VIRTUALIZATION_KVM) {
75f86906 LP	160
5dd6d0f8 LP	161	/* If we are not running in a container, see if we are
	162	* running in qemu/kvm and a machine ID was passed in
	163	* via -uuid on the qemu/kvm command line */
	164
75f86906	165	char uuid[36];
5dd6d0f8	166
75f86906 LP	167	fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY\|O_CLOEXEC\|O_NOCTTY\|O_NOFOLLOW);
	168	if (fd >= 0) {
	169	r = loop_read_exact(fd, uuid, 36, false);
	170	safe_close(fd);
5dd6d0f8	171
75f86906 LP	172	if (r >= 0) {
75f86906 LP	173	r = shorten_uuid(id, uuid);
a6dcc7e5	174	if (r >= 0) {
75f86906 LP	175	log_info("Initializing machine ID from KVM UUID.");
75f86906 LP	176	return 0;
5dd6d0f8 LP	177	}
	178	}
	179	}
0b36bbc4	180	}
d4eb120a LP	181	}
d4eb120a LP	182
d7ccca2e	183	/* If that didn't work, generate a random machine id */
87d2c1ff	184	r = sd_id128_randomize(&buf);
23bbb0de MS	185	if (r < 0)
23bbb0de MS	186	return log_error_errno(r, "Failed to open /dev/urandom: %m");
d7ccca2e	187
87d2c1ff	188	for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
d7ccca2e LP	189	q[0] = hexchar(*p >> 4);
	190	q[1] = hexchar(*p & 15);
	191	}
	192
	193	id[32] = '\n';
	194	id[33] = 0;
	195
	196	log_info("Initializing machine ID from random generator.");
	197
	198	return 0;
	199	}
	200
c6ac7e4b LP	201	int machine_id_setup(const char *root) {
	202	const char etc_machine_id, run_machine_id;
	203	_cleanup_close_ int fd = -1;
	204	bool writable = true;
	205	char id[34]; /* 32 + \n + \0 */
	206	int r;
9496e375	207
c6ac7e4b LP	208	if (isempty(root)) {
	209	etc_machine_id = "/etc/machine-id";
	210	run_machine_id = "/run/machine-id";
	211	} else {
	212	char *x;
9496e375	213
c6ac7e4b LP	214	x = strjoina(root, "/etc/machine-id");
c6ac7e4b LP	215	etc_machine_id = path_kill_slashes(x);
9496e375	216
c6ac7e4b LP	217	x = strjoina(root, "/run/machine-id");
c6ac7e4b LP	218	run_machine_id = path_kill_slashes(x);
9496e375 DR	219	}
9496e375 DR	220
c6ac7e4b LP	221	RUN_WITH_UMASK(0000) {
	222	/* We create this 0444, to indicate that this isn't really
	223	* something you should ever modify. Of course, since the file
	224	* will be owned by root it doesn't matter much, but maybe
	225	* people look. */
9496e375	226
c6ac7e4b LP	227	mkdir_parents(etc_machine_id, 0755);
	228	fd = open(etc_machine_id, O_RDWR\|O_CREAT\|O_CLOEXEC\|O_NOCTTY, 0444);
	229	if (fd < 0) {
	230	int old_errno = errno;
	231
	232	fd = open(etc_machine_id, O_RDONLY\|O_CLOEXEC\|O_NOCTTY);
	233	if (fd < 0) {
	234	if (old_errno == EROFS && errno == ENOENT)
	235	log_error_errno(errno,
	236	"System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
	237	"Booting up is supported only when:\n"
	238	"1) /etc/machine-id exists and is populated.\n"
	239	"2) /etc/machine-id exists and is empty.\n"
	240	"3) /etc/machine-id is missing and /etc is writable.\n");
	241	else
	242	log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
	243
	244	return -errno;
	245	}
9496e375	246
c6ac7e4b LP	247	writable = false;
	248	}
	249	}
	250
	251	if (read_machine_id(fd, id) >= 0)
9496e375 DR	252	return 0;
9496e375 DR	253
c6ac7e4b LP	254	/* Hmm, so, the id currently stored is not useful, then let's
	255	* generate one */
	256
	257	r = generate_machine_id(id, root);
	258	if (r < 0)
	259	return r;
	260
	261	if (writable)
	262	if (write_machine_id(fd, id) >= 0)
	263	return 0;
	264
	265	fd = safe_close(fd);
	266
	267	/* Hmm, we couldn't write it? So let's write it to
	268	* /run/machine-id as a replacement */
	269
	270	RUN_WITH_UMASK(0022) {
4c1fc3e4	271	r = write_string_file(run_machine_id, id, WRITE_STRING_FILE_CREATE);
c6ac7e4b LP	272	}
	273	if (r < 0) {
	274	(void) unlink(run_machine_id);
	275	return log_error_errno(r, "Cannot write %s: %m", run_machine_id);
	276	}
	277
	278	/* And now, let's mount it over */
	279	if (mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL) < 0) {
	280	(void) unlink_noerrno(run_machine_id);
	281	return log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
	282	}
	283
	284	log_info("Installed transient %s file.", etc_machine_id);
	285
	286	/* Mark the mount read-only */
	287	if (mount(NULL, etc_machine_id, NULL, MS_BIND\|MS_RDONLY\|MS_REMOUNT, NULL) < 0)
	288	log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);
	289
	290	return 0;
9496e375 DR	291	}
9496e375 DR	292
979ef53a DR	293	int machine_id_commit(const char *root) {
	294	_cleanup_close_ int fd = -1, initial_mntns_fd = -1;
	295	const char *etc_machine_id;
	296	char id[34]; /* 32 + \n + \0 */
	297	int r;
	298
	299	if (isempty(root))
	300	etc_machine_id = "/etc/machine-id";
	301	else {
	302	char *x;
	303
63c372cb	304	x = strjoina(root, "/etc/machine-id");
979ef53a DR	305	etc_machine_id = path_kill_slashes(x);
	306	}
	307
e26d6ce5	308	r = path_is_mount_point(etc_machine_id, 0);
979ef53a	309	if (r < 0)
f131770b	310	return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", etc_machine_id);
979ef53a DR	311	if (r == 0) {
	312	log_debug("%s is is not a mount point. Nothing to do.", etc_machine_id);
	313	return 0;
	314	}
	315
	316	/* Read existing machine-id */
	317	fd = open(etc_machine_id, O_RDONLY\|O_CLOEXEC\|O_NOCTTY);
	318	if (fd < 0)
	319	return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
	320
c6ac7e4b	321	r = read_machine_id(fd, id);
979ef53a DR	322	if (r < 0)
	323	return log_error_errno(r, "We didn't find a valid machine ID in %s.", etc_machine_id);
	324
c6878637	325	r = fd_is_temporary_fs(fd);
979ef53a DR	326	if (r < 0)
	327	return log_error_errno(r, "Failed to determine whether %s is on a temporary file system: %m", etc_machine_id);
	328	if (r == 0) {
	329	log_error("%s is not on a temporary file system.", etc_machine_id);
	330	return -EROFS;
	331	}
	332
	333	fd = safe_close(fd);
	334
	335	/* Store current mount namespace */
671c3419	336	r = namespace_open(0, NULL, &initial_mntns_fd, NULL, NULL, NULL);
979ef53a DR	337	if (r < 0)
	338	return log_error_errno(r, "Can't fetch current mount namespace: %m");
	339
	340	/* Switch to a new mount namespace, isolate ourself and unmount etc_machine_id in our new namespace */
	341	if (unshare(CLONE_NEWNS) < 0)
	342	return log_error_errno(errno, "Failed to enter new namespace: %m");
	343
	344	if (mount(NULL, "/", NULL, MS_SLAVE \| MS_REC, NULL) < 0)
	345	return log_error_errno(errno, "Couldn't make-rslave / mountpoint in our private namespace: %m");
	346
	347	if (umount(etc_machine_id) < 0)
	348	return log_error_errno(errno, "Failed to unmount transient %s file in our private namespace: %m", etc_machine_id);
	349
	350	/* Update a persistent version of etc_machine_id */
	351	fd = open(etc_machine_id, O_RDWR\|O_CREAT\|O_CLOEXEC\|O_NOCTTY, 0444);
	352	if (fd < 0)
	353	return log_error_errno(errno, "Cannot open for writing %s. This is mandatory to get a persistent machine-id: %m", etc_machine_id);
	354
	355	r = write_machine_id(fd, id);
	356	if (r < 0)
	357	return log_error_errno(r, "Cannot write %s: %m", etc_machine_id);
	358
	359	fd = safe_close(fd);
	360
	361	/* Return to initial namespace and proceed a lazy tmpfs unmount */
671c3419	362	r = namespace_enter(-1, initial_mntns_fd, -1, -1, -1);
979ef53a DR	363	if (r < 0)
	364	return log_warning_errno(r, "Failed to switch back to initial mount namespace: %m.\nWe'll keep transient %s file until next reboot.", etc_machine_id);
	365
	366	if (umount2(etc_machine_id, MNT_DETACH) < 0)
	367	return log_warning_errno(errno, "Failed to unmount transient %s file: %m.\nWe keep that mount until next reboot.", etc_machine_id);
	368
	369	return 0;
	370	}