[pkg-cryptsetup-devel] Bug#902449: cryptsetup-initramfs: auto-detection of zfs pool(s)

[Guilhem Moulin]

On Thu, 05 Jul 2018 at 11:05:08 +0200, Michal Humpula wrote:
>> Since ZFS doesn't expose a block device one would need another
>> documented way to resolve /sys/fs/zfs/$FS.  Hopefully ‘tank/my/fs’ is
>> unique and can't be aliased to something else, can it?
> 
>> Do the slash characters in ‘tank/my/fs’ hint at a hierarchy, or is it a
>> flat string?
> 
> It's unique and designates the ZFS specific fs instance which is hierarchical. 
> First level is the zpool name. As far as I know btrfs has something similar 
> with subvolumes. Below is an example of zfs list
> 
> NAME                       USED  AVAIL  REFER  MOUNTPOINT
> tank                      2,45T   189G   120K  /tank
> tank/backup               75,8G   189G   136K  /tank/backup
> tank/data                 1,91T   189G  1,83T  /tank/data
> tank/home                  122G   189G  42,2G  /home
> tank/root                  148G   189G  13,9G  /

If it's like btrfs subvolumes the zpool (‘tank’) denotes the FS itself,
while the subhierarchy denotes different views of it.

I guess ‘tank’, ‘tank/backup’, ‘tank/data’ etc. need to have the same
set of features enabled, and that the same underlying devices?  In that,
case, I think FS="tank" would be better than FS="tank/my/fs".
Conveniently this also trims the hierarchy :-)

-- 
Guilhem.
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