Re: How do I specify a btrfs subvolume?

[raingloom]

On Sun, 14 Mar 2021 20:33:06 -0500
Nathan Dehnel <ncdehnel@gmail.com> wrote:

> This is extremely confusing:
> https://guix.gnu.org/manual/en/html_node/Btrfs-file-system.html
> 
> I made my best attempt at creating and mounting a subvolume at
> /media/offsite-backup:
> 
>   (file-systems
>     (cons* (file-system
>              (mount-point "/")
>              (device
>                (uuid "b2e0f449-0583-46fd-8c23-ad2e6cd661a1"
>                      'btrfs))
>              (type "btrfs"))
>            (file-system
>              (mount-point "/media/offsite-backup")
>              (device
>                (uuid "b2e0f449-0583-46fd-8c23-ad2e6cd661a1"
>                      'btrfs))
>              (type "btrfs")
>              (options "subvol=offsite-backup,compress=zlib:9"))
> 
> It gives this error:
> 
> building
> /gnu/store/mrs1qbg619qk4n2lv8k377arclgzwqjq-install-bootloader.scm.drv...
> guix system: bootloader successfully installed on '/dev/sda' guix
> system: warning: exception caught while executing 'start' on service
> 'file-system-/media/offsite-backup': In procedure mount: mount
> "/dev/sda2" on "///media/offsite-backup": No such file or directory
> guix system: warning: some services could not be upgraded
> 
> But /media/offsite-backup exists.
> 

I'm looking at
https://wiki.archlinux.org/index.php/Btrfs#Mounting_subvolumes
and it seems like you either need a numberic ID or an absolute path,
not a relative one.
On my machine `findmnt` returns `subvol=/`.