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#1 2019-05-31 20:12:06

garbageof
Member
Registered: 2019-05-31
Posts: 3

[solved] Can't mount btrfs subvolume with user_subvol_rm_allowed?

Hi there,

this is my first forum post, i can't find any "welcome new users" 3ad.

I use arch on my vps with lxd and i like it a lot but i have a little problem with the mount options "user_subvol_rm_allowed" (https://btrfs.wiki.kernel.org/index.php … NT_OPTIONS), i wasn't able to mount with this options (very usefully with docker on nesting container)

this is my test:

mounting manually:

 mount -t btrfs -o rw,noatime,compress=lzo,user_subvol_rm_allowed,subvolid=262,subvol=/@lxdstuff,subvol=@lxdstuff /DATA/lxd 

result: no option

 mount|grep lxd
/dev/mapper/archlinux on /DATA/backup/lxd type btrfs (rw,noatime,compress=lzo,ssd,space_cache,subvolid=320,subvol=/@DATA/backup/lxd)
/dev/mapper/archlinux on /DATA/lxd type btrfs (rw,noatime,compress=lzo,ssd,space_cache,subvolid=262,subvol=/@lxdstuff) 

fstab:

# <file system> <dir> <type> <options> <dump> <pass>
LABEL=vps     	/         	btrfs     	rw,noatime,compress=lzo,ssd,space_cache,subvolid=257,subvol=/@,subvol=@	0 0

LABEL=vps     	/home     	btrfs     	rw,noatime,compress=lzo,ssd,space_cache,subvolid=258,subvol=/@home,subvol=@home0 0

LABEL=vps     	/.snapshots	btrfs     	rw,noatime,compress=lzo,ssd,space_cache,subvolid=259,subvol=/@snapshots,subvol=@snapshots	0 0

LABEL=vps     	/DATA     	btrfs     	rw,noatime,compress=lzo,user_subvol_rm_allowed,ssd,space_cache,subvolid=261,subvol=/@DATA,subvol=@DATA	0 0

LABEL=vps     	/var/cache/pacman/pkg	btrfs     	rw,noatime,compress=lzo,ssd,space_cache,subvolid=260,subvol=/@pacmancache,subvol=@pacmancache	0 0
# lxd
LABEL=vps     	/DATA/lxd	btrfs     	rw,noatime,compress=lzo,user_subvol_rm_allowed,ssd,space_cache,subvolid=262,subvol=/@lxdstuff,subvol=@lxdstuff 	0 0
# lxdbackup
LABEL=vps     	/DATA/backup/lxd	btrfs     	rw,noatime,compress=lzo,ssd,space_cache,subvolid=320,subvol=/@DATA/backup/lxd,subvol=@DATA/backup/lxd 0 0 

same result, why the options is ignored?
kernel = 5.1.5-arch1-2-ARCH

many thanks

Last edited by garbageof (2019-06-01 13:35:08)

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#2 2019-06-01 12:15:16

garbageof
Member
Registered: 2019-05-31
Posts: 3

Re: [solved] Can't mount btrfs subvolume with user_subvol_rm_allowed?

Today i tried with linux-lts and linux-zen, same result

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#3 2019-06-01 13:10:02

Ropid
Member
Registered: 2015-03-09
Posts: 1,069

Re: [solved] Can't mount btrfs subvolume with user_subvol_rm_allowed?

As an experiment, try adding the mount option in your fstab entry for "/". Then restart and check how things look like in the output of "mount".

The idea would be to check if this mount option can maybe exist only once for the whole btrfs filesystem. There are other btrfs mount options where I noticed this behavior. For those mount options it then doesn't matter what you do in your fstab for different subvolumes, instead all subvolumes will inherit the option from the first subvolume you mount.

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#4 2019-06-01 13:34:35

garbageof
Member
Registered: 2019-05-31
Posts: 3

Re: [solved] Can't mount btrfs subvolume with user_subvol_rm_allowed?

Ropid wrote:

As an experiment, try adding the mount option in your fstab entry for "/". Then restart and check how things look like in the output of "mount".

The idea would be to check if this mount option can maybe exist only once for the whole btrfs filesystem. There are other btrfs mount options where I noticed this behavior. For those mount options it then doesn't matter what you do in your fstab for different subvolumes, instead all subvolumes will inherit the option from the first subvolume you mount.

Thanks Ropid, worked like a charm smile

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