systemd-machine-id-commit.service

systemd
systemd-machine-id-commit.service 8
systemd-machine-id-commit.service Commit a transient machine ID to disk

`systemd-machine-id-commit.service`

## Description

`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.

## See Also

systemd 1, systemd-machine-id-setup 1, machine-id 5, systemd-firstboot 1