Re: finding root filesystem of a subvolume?

[Hugo Mills <hugo@carfax.org.uk>]

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On Tue, Aug 22, 2017 at 02:23:50PM +0200, Ulli Horlacher wrote:
> How do I find the root filesystem of a subvolume?
> Example:
> 
> root@fex:~# df -T 
> Filesystem     Type  1K-blocks      Used Available Use% Mounted on
> -              -    1073740800 104244552 967773976  10% /local/.backup/home

   I've never seen the "- -" output from df before. Is this a bind
mount or something?

> root@fex:~# btrfs subvolume show /local/.backup/home
> /local/.backup/home
>         Name:                   home
>         uuid:                   f86a2db0-6a82-124f-9a71-1cd4c20fd6fb
>         Parent uuid:            ba4d388f-44bf-7b46-b2b8-00e2a9a87181
>         Creation time:          2017-08-10 22:19:15
>         Object ID:              383
>         Generation (Gen):       148
>         Gen at creation:        148
>         Parent:                 5
>         Top Level:              5
>         Flags:                  readonly
>         Snapshot(s):
> 
> 
> I know, the root filesystem is /local, but who can I show it by command?

   Probably in /proc/self/mountinfo -- that should give you the full
set of applied mount options, plus the original source for the mount
(which will be a block device for most filesystem mounts, a path for
bind mounts, or something FS-specific for network filesystems).

   Hugo.

-- 
Hugo Mills             | And what rough beast, its hour come round at last /
hugo@... carfax.org.uk | slouches towards Bethlehem, to be born?
http://carfax.org.uk/  |
PGP: E2AB1DE4          |                         W.B. Yeats, The Second Coming

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