Allow for overriding all other machine-ids which may be present on
the system using a kernel command line systemd.machine_id or
--machine-id= option.
This is especially useful for network booted systems where the
machine-id needs to be static, or for containers where a specific
machine-id is wanted.
If /etc was read only at boot time with an empty /etc/machine-id, the latter
will be mounted as a tmpfs and get reset at each boot. If the system becomes rw
later, this functionality enables to commit in a race-free manner the
transient machine-id to disk.
This makes it possible to initialize the /etc/machine-id file on an
arbitrary filesystem hierarchy. This helps systems that wish to run
this at image creation time in a subdirectory, or from initramfs before
pivot-root is called.
[tomegun: converted to using _cleanup_free_ macros]
#pragma once has been "un-deprecated" in gcc since 3.3, and is widely supported
in other compilers.
I've been using and maintaining (rebasing) this patch for a while now, as
it annoyed me to see #ifndef fooblahfoo, etc all over the place,
almost arrogant about the annoyance of having to define all these names to
perform a commen but neccicary functionality, when a completely superior
alternative exists.
I havn't sent it till now, cause its kindof a style change, and it is bad
voodoo to mess with style that has been established by more established
editors. So feel free to lambast me as a crazy bafoon.
v2 - preserve externally used headers
Lennart Poettering
Daniel Mack
Nils Carlson
Didier Roche
Greg KH
Shawn Landden