[arch-general] Stateless Arch

[Tom Gundersen]

On Mon, Jul 9, 2012 at 10:10 AM, Damjan <gdamjan at gmail.com> wrote:
> Has anyone done any research on stateless ArchLinux instances.
>
> A stateless Arch would be one where the root filesystem is mounted read-only
> and nothing changes there. Thus it can mounted over network (using NFS, NBD
> and similar) by several, diskless, PCs at the same time.
>
> I plan to have per user HOME directories on a server (again NFS or similar),
> and users credentials in LDAP.
>
> /var/run beeing a link to a tmpfs /run, and by using systemd-journal without
> /var/log/journal (it will store logs in memory) a lot of things avoid
> hitting the disk already.
>
> I'd use connman for handling the net connection and it seems to require a
> writable /var/lib/connman/
>
>
> Anyone with any experience with this?

I have been working towards initscripts allowing this, and various
upstreams (such as util-linux) should also support this setup. That
said, I have not actually tested this to any great extent, so don't
know how well it will work (feedback very welcome!).

What should work (but might not!): /etc and /usr (and /lib, /sbin,
/bin) should be able to be mounted read-only. I expect you'll have to
figure out how to deal with /etc/resolv.conf, I wonder if
NetworkManager has learnt how to deal with this gracefully since I
last checked...

What will not work: as Rodrigo said, you'll still need /var to be
mounted read-write, the point of /var is for applications to be able
to write to it. Moreover, /var must be unique to each installation,
and cannot be shared (you can put it on an NFS share though, just make
sure you have one for each machine). Moreover, even if /etc/ is
mounted read-only, you probably want one per machine. You might get
away with sharing it, but then all your hostnames will be the same for
instance. Importantly: you don't want /etc/machine-id to be shared by
different machines (as it needs to be unique). If you do decide to
share /etc, you can replace /etc/machine-id by an empty file and
systemd will create a random one at every boot (in /run) and use that
instead, so you should be fine in this respect.

HTH,

Tom