Index · Directives · Python · libudev · gudev systemd 220

## Name

systemd-machine-id-commit.service — Commit transient machine-id to disk

## Synopsis

`systemd-machine-id-commit.service`

`/usr/lib/systemd/systemd-machine-id-commit`

## Description

`systemd-machine-id-commit.service` is a service responsible for committing any transient `/etc/machine-id` file to a writable file system. See machine-id(5) for more information about this file.

This service is started shortly after `local-fs.target` if `/etc/machine-id` is an independent mount point (probably a tmpfs one) and /etc is writable. systemd-machine-id-commit will then write current machine ID to disk and unmount the transient `/etc/machine-id` file in a race-free manner to ensure that file is always valid for other processes.

Note that the traditional way to initialize the machine ID in `/etc/machine-id` is to use systemd-machine-id-setup by system installer tools. You can also use systemd-firstboot(1) to initialize the machine ID on mounted (but not booted) system images. The main use case for that service is `/etc/machine-id` being an empty file at boot and initrd chaining to systemd giving it a read only file system that will be turned read-write later during the boot process.

There is no consequence if that service fails other than a newer machine-id will be generated during next system boot.

## See Also

systemd(1), systemd-machine-id-commit(1), systemd-machine-id-setup(1), machine-id(5), systemd-firstboot(1)