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