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nspawn: rework /etc/machine-id handling

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With this change we'll no longer write to /etc/machine-id from nspawn, as that
breaks the --volatile= operation, as it ensures the image is never considered
in "first boot", since that's bound to the pre-existance of /etc/machine-id.

The new logic works like this:

- If /etc/machine-id already exists in the container, it is read by nspawn and
  exposed in "machinectl status" and friends.

- If the file doesn't exist yet, but --uuid= is passed on the nspawn cmdline,
  this UUID is passed in $container_uuid to PID 1, and PID 1 is then expected
  to persist this to /etc/machine-id for future boots (which systemd already
  does).

- If the file doesn#t exist yet, and no --uuid= is passed a random UUID is
  generated and passed via $container_uuid.

The result is that /etc/machine-id is never initialized by nspawn itself, thus
unbreaking the volatile mode. However still the machine ID configured in the
machine always matches nspawn's and thus machined's idea of it.

Fixes: #3611
This commit is contained in:
Lennart Poettering 2016-07-21 18:53:40 +02:00
parent 2a6736ddd0
commit 317feb4d9f
2 changed files with 30 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Makefile.am
View File

@ -3075,9 +3075,7 @@ systemd_nspawn_SOURCES = \
src/core/mount-setup.c \
src/core/mount-setup.h \
src/core/loopback-setup.c \
src/core/loopback-setup.h \
src/core/machine-id-setup.c \
src/core/machine-id-setup.h
src/core/loopback-setup.h
nodist_systemd_nspawn_SOURCES = \
src/nspawn/nspawn-gperf.c

55
src/nspawn/nspawn.c
View File

@ -64,7 +64,6 @@
#include "id128-util.h"
#include "log.h"
#include "loopback-setup.h"
#include "machine-id-setup.h"
#include "machine-image.h"
#include "macro.h"
#include "missing.h"
@ -595,9 +594,12 @@ static int parse_argv(int argc, char *argv[]) {
case ARG_UUID:
r = sd_id128_from_string(optarg, &arg_uuid);
if (r < 0) {
log_error("Invalid UUID: %s", optarg);
return r;
if (r < 0)
return log_error_errno(r, "Invalid UUID: %s", optarg);
if (sd_id128_is_null(arg_uuid)) {
log_error("Machine UUID may not be all zeroes.");
return -EINVAL;
}
arg_settings_mask |= SETTING_MACHINE_ID;
@ -2219,37 +2221,38 @@ static int mount_device(const char *what, const char *where, const char *directo
#endif
}
static int machine_id_read(const char *directory, sd_id128_t *ret) {
static int setup_machine_id(const char *directory) {
const char *etc_machine_id;
sd_id128_t id;
int r;
/* If the UUID in the container is already set, then that's what counts, and we use. If it isn't set, and the
* caller passed --uuid=, then we'll pass it in the $container_uuid env var to PID 1 of the container. The
* assumption is that PID 1 will then write it to /etc/machine-id to make it persistent. If --uuid= is not
* passed we generate a random UUID, and pass it via $container_uuid. In effect this means that /etc/machine-id
* in the container and our idea of the container UUID will always be in sync (at least if PID 1 in the
* container behaves nicely). */
etc_machine_id = prefix_roota(directory, "/etc/machine-id");
r = id128_read(etc_machine_id, ID128_PLAIN, &id);
if (r < 0)
return r;
if (r < 0) {
if (!IN_SET(r, -ENOENT, -ENOMEDIUM)) /* If the file is missing or empty, we don't mind */
return log_error_errno(r, "Failed to read machine ID from container image: %m");
if (sd_id128_is_null(id))
return -EINVAL;
if (sd_id128_is_null(arg_uuid)) {
r = sd_id128_randomize(&arg_uuid);
if (r < 0)
return log_error_errno(r, "Failed to acquire randomized machine UUID: %m");
}
} else {
if (sd_id128_is_null(id)) {
log_error("Machine ID in container image is zero, refusing.");
return -EINVAL;
}
*ret = id;
return 0;
}
static int setup_machine_id(const char *directory) {
int r;
/* Try to set up the machine ID, if it isn't set up yet. Use a transient one, if necessary. Use the the UUID we
* were configured for if possible for initialization. */
r = machine_id_setup(directory, arg_uuid);
if (r < 0)
return log_error_errno(r, "Failed to setup machine ID: %m");
/* Read back what was actually set. */
r = machine_id_read(directory, &arg_uuid);
if (r < 0)
return log_error_errno(r, "Failed to read machine ID: %m");
arg_uuid = id;
}
return 0;
}