DynamicUsers and read-only /var

[walters@xxxxxxxxxx (Colin Walters)]

On Wed, May 16, 2018, at 10:56 AM, Simon McVittie wrote:
> 
> Projects like libostree and rpm-ostree might have some useful concepts
> or code for managing immutable, read-only rootfs or /usr deployments,
> since that's what they do: in an ostree-based OS, /usr is an
> atomically-updated immutable tree, directories like /var and /home are
> locally-maintained, and /etc is a three-way merge between the old
> /usr/etc, the new /usr/etc and the local /etc.

Yep, the libostree manual suggests converting contents in /var to systemd
tmpfiles snippets:

https://ostree.readthedocs.io/en/latest/manual/adapting-existing/

And that's in fact what rpm-ostree does: 

https://github.com/projectatomic/rpm-ostree/blob/bff3a54e1ee67398bd7a2cfdc359326689479954/src/libpriv/rpmostree-postprocess.c#L556