systemd-machine-id-commit.service — Commit a transient machine ID to disk
systemd-machine-id-commit.service
systemd-machine-id-commit.service is an
early boot service responsible for committing transient
/etc/machine-id files to a writable disk file
system. See
machine-id(5)
for more information about machine IDs.
This service is started after
local-fs.target in case
/etc/machine-id is a mount point of its own
(usually from a memory file system such as
"tmpfs") and /etc is writable. The service will
invoke systemd-machine-id-setup --commit, which
writes the current transient machine ID to disk and unmount the
/etc/machine-id file in a race-free manner to
ensure that file is always valid and accessible for other
processes. See
systemd-machine-id-setup(1)
for details.
The main use case of this service are systems where
/etc/machine-id is read-only and initially
not initialized. In this case, the system manager will generate a
transient machine ID file on a memory file system, and mount it
over /etc/machine-id, during the early boot
phase. This service is then invoked in a later boot phase, as soon
as /etc/ has been remounted writable and the
ID may thus be committed to disk to make it permanent.