Introduce lxc.storage.<storage-driver>.* type configuration for container storage

[Harvie]

Hello i am trying to use ZFS or BtrFS with LXC and i've sucesfully set up ZFS like this:

lxc.lxcpath = /var/lib/lxc
lxc.bdev.zfs.root = tank/containers

But i have to call lxc-create with "-B zfs" each time and that sux. It's not going to change very often and when i let someone to manage the server and they forget about this they can just create dir without creating ZFS by omiting the "-B zfs" by accident.

Is there some place to set this? If not please add ability to set it like "lxc.backingstore=zfs" in lxc.conf.

Also please make the "best" backing store the new default (as it should use ZFS or BTRFS automaticaly when available).

[brauner]

Hm, I'm very much against configuration key inflation so I'm not very supportive of this idea. @stgraber and @hallyn may however disagree. In any case, if they agree with you and you want this option we welcome patches. :)

[hallyn]

Well as it is we have lxc.bdev.lvm.vg and lxc.bdev.zfs.root in lxc.system.conf.

lxc..backingstore= doesn't sound bad to me, assuming hooking it into the container creation doesn't become too invasive.

[stgraber]

+1 on @hallyn's comment. We have the other bdev bits in there already and having to always pass -B is a bit counter-intuitive, so I'd be fine with adding an option.

[ek9]

+1, the -B btrfs has been typed too many times in this terminal.

[hallyn]

So to summarize - patches welcome :)

[anevenchanniy]

We are already have bdevtype inside LXC code, so lxc.bdev.type=[lvm,btrfs,zfs etc]
looks like more preferable, as for me.
https://github.com/lxc/lxc/blob/master/src/lxc/tools/lxc_create.c#L73

[hallyn]

@anevenchanniy - I agree about lxc.bdev.type. While bdev is not as descriptive as 'backingstore', I think avoiding different option names for the config file than the command line options is worthwhile.

[brauner]

@hallyn, @stgraber, since I'm currently working on rewriting the storage backends for LXC as well. I would pick this idea up. But I would introduce the following namespaces keys:

lxc.storage.<storage driver>.*

For example

lxc.storage.zfs.pool
lxc.storage.btrfs.pool
lxc.storage.zfs.clone_copy
lxc.storage.ceph.osd.pool_name

etc. This nicely aligns with LXD and will make the API way nicer. Hooking it into the current container creation shouldn't be too difficult from an API perspective. In fact, it should make container creation and copy way easier.

[hallyn]

Quoting Christian Brauner (notifications@github.com):

@hallyn, @stgraber, since I'm currently working on rewriting the storage backends for LXC as well. I would pick this idea up. But I would introduce the following namespaces keys: lxc.storage.<storage driver>.* For example lxc.storage.zfs.pool lxc.storage.btrfs.pool lxc.storage.zfs.clone_copy lxc.storage.ceph.osd.pool_name etc. This nicely aligns with `LXD` and will make the API way nicer. Hooking it into the current container creation shouldn't be too difficult from an API perspective. In fact, it should make container creation and copy way easier.

wfm