Re: partman, growlight, discoverable partitions, and fun

[Wouter Verhelst <wouter@debian.org>]

On Tue, Sep 28, 2021 at 06:19:28AM -0400, nick black wrote:
> Wouter Verhelst left as an exercise for the reader:
> > One thing that partman does is "support plug-ins", to allow for
> > configuring block devices before being able to partition them, where
> > needed. This can be useful for iSCSI, multipath, or (the one I care most
> > about) NBD. I wrote a "partman-nbd" a few years back to do just that:
> > https://salsa.debian.org/installer-team/partman-nbd
> 
> Thanks a lot for pointing this out, Wouter -- this is *exactly*
> the kind of feedback I was hoping for! I allow loopback devices
> to be set up, but not in any reboot-crossing manner, and I have
> no NBD nor iSCSI functionality.
> 
>  https://github.com/dankamongmen/growlight/issues/150

NBD is fairly easy to set up (well, it is for me, but then I'm biased).
For the server side, you install nbd-server, you create a (probably
sparse) large file somewhere, and then edit /etc/nbd-server/config to
point to that. For the client side, you install nbd-client and read "man
5 nbdtab" if you want to persist things, or you read "man 8 nbd-client"
if you just want to connect now and not care about reboot.

iSCSI works very differently and is way more complex, but I remember
from when I last played with it (which is a while ago, so the details
are hazy) that it's not possible to set up in a non-persistent manner
(i.e., all iSCSI connections survive reboot unless explicitly deleted,
although obviously partman-iscsi has to do some dark magic to ensure the
configuration is migrated from the d-i environment to the live system).

There's also ATA-over-Ethernet, Fibrechannel-over-ethernet, multipath,
and a whole slew of other things, if you want to configure this from
growlight.

That said though, I would personally recommend against doing that. From
where I'm standing, it seems to be out of scope for growlight? If you're
replacing partman in d-i, you'd still need to add *some* d-i
integration, and I'd imagine that integration is where this type of
device configuration would go. As far as running growlight outside of
d-i goes, there I'd think you'd just tell the user to configure the
device before starting growlight (or you'd give them the ability to
re-scan for new devices after they'd set up the device in a (different)
terminal), and then that'll be all? Otherwise you'll end up with a
neverending story of "oh here's another type of device that needs to be
added", and I don't think that's a great rabbit hole to go down.

I could be wrong though, haven't looked at growlight in much detail, and
in the end it's your call, not mine :-D

-- 
     w@uter.{be,co.za}
wouter@{grep.be,fosdem.org,debian.org}