What's this /run directory doing on my system and where does it come from?

[Peter Jones]

On 03/30/2011 07:54 AM, Lennart Poettering wrote:
> Heya,
> 
> I just uploaded a new version of systemd into F15, which establishes a
> directory /run in the root directory. Most likely you'll sooner or later
> stumble over it, so here's an explanation what this is and why this is.
> 
> It's a fairly minor technical change, though presumably people consider
> this a bigger political change, so I guess this deserves an
> explanation:
> 
> For quite a while programs involved with early boot used to place
> runtime data in /dev under numerous hidden dot directories. /dev/.udev
> was the first one, but over time this grew to at least /dev/.mdadm,
> /dev/.systemd, /dev/.mount, dracut, initscripts and more tools. (Other
> distros have even more) The reason they used directories there is that
> /dev was known to be a tmpfs and available from the first instant the
> machine was booted. /var/run otoh is only available very late at
> boot, since /var might reside on a separate file system.

Just for some perspective, before /dev/.udev we had /dev/.dhclient-leases
and before even that we had /initrd for quite some time.

There's nothing new under the sun.

-- 
        Peter