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machine-id-setup: acquire machine ID from /run/machine-id if possible

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If machine ID is previously stored at /run/machine-id, then let's reuse
it. This is important on switching root and /etc/machine-id was previously
a mount point.

Fixes #32908.
This commit is contained in:
Yu Watanabe 2024-05-19 09:14:27 +09:00
parent ba540e9f1c
commit 16718dcf78
1 changed files with 24 additions and 13 deletions
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27
src/shared/machine-id-setup.c
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@ -48,13 +48,22 @@ static int acquire_machine_id_from_credential(sd_id128_t *ret) {
return 0;
}
static int generate_machine_id(const char *root, sd_id128_t *ret) {
static int acquire_machine_id(const char *root, sd_id128_t *ret) {
_cleanup_close_ int fd = -EBADF;
int r;
assert(ret);
/* First, try reading the D-Bus machine id, unless it is a symlink */
/* First, try reading the machine ID from /run/machine-id, which may not be mounted on
* /etc/machine-id yet. This is important on switching root, Otherwise, machine ID may be changed
* after the transition. */
if (empty_or_root(root) && running_in_chroot() <= 0 &&
id128_read("/run/machine-id", ID128_FORMAT_PLAIN, ret) >= 0) {
log_info("Reusing machine ID stored in /run/machine-id.");
return 1; /* Indicate that the machine ID is reused. */
}
/* Then, try reading the D-Bus machine id, unless it is a symlink */
fd = chase_and_open("/var/lib/dbus/machine-id", root, CHASE_PREFIX_ROOT | CHASE_NOFOLLOW, O_RDONLY|O_CLOEXEC|O_NOCTTY, NULL);
if (fd >= 0 && id128_read_fd(fd, ID128_FORMAT_PLAIN | ID128_REFUSE_NULL, ret) >= 0) {
log_info("Initializing machine ID from D-Bus machine ID.");
@ -63,9 +72,8 @@ static int generate_machine_id(const char *root, sd_id128_t *ret) {
if (empty_or_root(root) && running_in_chroot() <= 0) {
/* Let's use a system credential for the machine ID if we can */
r = acquire_machine_id_from_credential(ret);
if (r >= 0)
return r;
if (acquire_machine_id_from_credential(ret) >= 0)
return 0;
/* 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
@ -105,7 +113,7 @@ static int generate_machine_id(const char *root, sd_id128_t *ret) {
int machine_id_setup(const char *root, bool force_transient, sd_id128_t machine_id, sd_id128_t *ret) {
const char *etc_machine_id, *run_machine_id;
_cleanup_close_ int fd = -EBADF;
bool writable;
bool writable, write_run_machine_id = true;
int r;
etc_machine_id = prefix_roota(root, "/etc/machine-id");
@ -146,10 +154,11 @@ int machine_id_setup(const char *root, bool force_transient, sd_id128_t machine_
if (id128_read_fd(fd, ID128_FORMAT_PLAIN, &machine_id) >= 0)
goto finish;
/* Hmm, so, the id currently stored is not useful, then let's generate one */
r = generate_machine_id(root, &machine_id);
/* Hmm, so, the id currently stored is not useful, then let's acquire one. */
r = acquire_machine_id(root, &machine_id);
if (r < 0)
return r;
write_run_machine_id = !r;
}
if (writable) {
@ -187,12 +196,14 @@ int machine_id_setup(const char *root, bool force_transient, sd_id128_t machine_
run_machine_id = prefix_roota(root, "/run/machine-id");
if (write_run_machine_id) {
WITH_UMASK(0022)
r = id128_write(run_machine_id, ID128_FORMAT_PLAIN, machine_id);
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 */
r = mount_follow_verbose(LOG_ERR, run_machine_id, etc_machine_id, NULL, MS_BIND, NULL);