Support Logical Volume (LV) as Target

[globalcitizen]

Rough thinking at present is:

• Best to leave LV creation out of scope (VG validation, size specification, availability checking, filesystem selection and create-time filesystem options, etc.)
• LV is mounted temporarily if required (normal mount is expected to correctly detect the filesystem type)
• Root filesystem cache is copied there instead of the subdir

[EvaSDK]

You most likely want to handle brtfs volumes as well for btrfs aficionados :)
If you are a zfs fan, this is mostly something to handle as well and should be similarly done.
Last but not least, one thing that current lxc-create does not handle is lvm thin volume or whatever is the feature again to create a minimal image to bootstrap your new volume with copy-on-write internally which should speed things up a fair bit.

[globalcitizen]

OK, so...

• Arbitrary filesystem support is desirable.
• I can see autodetection of installed filesystems with /proc/filesystems ...
• I worry that some of them and advanced users will require create-time options that will cause the naive approach of mkfs.${FILESYSTEM} /dev/target to fail
• Thinking of creating mkfs.${FILESYSTEM} as a default command line, prompting the user to confirm (ie. they can add custom options, have a script handle free space calculations, quotas, advanced creation logic, etc.)
• Any recommended defaults that differ from mkfs.${FILESYSTEM} could be rolled in to lxc-gentoo for filesystems on which that is always a bad idea

Snapshot and thin provisioning support segmented to issue #42.