Can't Make a Subvolume in Home Folder?

[PhysicistSarah]

I'm trying to make a subvolume in my home folder but I keep getting an error saying that it is not a btrfs filesystem. This is strange because @home exists, so clearly, the disk is btrfs.

[FONT=monospace][COLOR=#54FF54][B]sarah@ConvergentRefuge[/B][/COLOR]:[COLOR=#5454FF][B]~[/B][/COLOR]$ btrfs subvolume create ARC 
ERROR: not a btrfs filesystem: . 
[COLOR=#54FF54][B]sarah@ConvergentRefuge[/B][/COLOR]:[COLOR=#5454FF][B]~[/B][/COLOR]$ sudo btrfs subvolume list / 
ID 257 gen 405646 top level 5 path @ 
ID 258 gen 405646 top level 5 path @home

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[jlittle]

Well, in principle, just because the @home subvolume exists does not preclude your home directory being somewhere else, and your prompt saying "~" could be lying. What do these say:

$ pwd
$ sudo blkid
$ findmnt -s

I ran your command in my home directory successfully. Odd that one can create a subvolume without sudo.

[oshunluvr]

My home is in it's own subvolume and:

stuart@Precision7730:/etc/NetworkManager$ cd /home
stuart@Precision7730:/home$ cd stuart
stuart@Precision7730:~$ btrfs su cr ARC
Create subvolume './ARC'
stuart@Precision7730:~$

No sudo or anything special required. The only difference that sticks out is I have the root volume mounted. Try mounting your root filesystem somewhere (I use /mnt/subvols) and try again.

[oshunluvr]

Interestingly, sudo not required to create it but WAS required to delete it.

[kubicle]

Interestingly, sudo not required to create it but WAS required to delete it.

"man mount" (btrfs mount options):

user_subvol_rm_allowed
Allow subvolumes to be deleted by a non-root user. Use with caution.

[oshunluvr]

Interesting tidbit - learn something new every day. Still, I hadn't mounted it so the mount option wouldn't apply if I understand your post correctly.

[kubicle]

Interesting tidbit - learn something new every day. Still, I hadn't mounted it so the mount option wouldn't apply if I understand your post correctly.

The mount option refers to the parent filesystem, not the subvolume you're gonna delete, if your subvolumes reside under @home, for example, then if @home is mounted with the mount option (you can remount it with it, or define the option in fstab), the subvolumes can be removed as a user...but use with caution, as advised in the man page.

$ btrfs subvolume create test
Create subvolume './test'

$ btrfs subvolume delete test
Delete subvolume (no-commit): '/home/user/test'
ERROR: cannot delete '/home/user/test': Operation not permitted

$ sudo mount -o  remount,rw,relatime,ssd,space_cache,subvolid=257,subvol=/@home,user_subvol_rm_allowed   /home

$ btrfs subvolume delete test
Delete subvolume (no-commit): '/home/user/test'

[oshunluvr]

Ah, makes sense. Thanks for the explanation. It does sound like a dangerous thing to use unwisely. Still, it seems illogical that a user can create a subvolume in their userspace but can't delete it.

[PhysicistSarah]

Here is mine. The pwd is clearly /home/sarah and the /home folder is a btrfs filesystem, so...?

[FONT=monospace][COLOR=#54FF54][B]sarah@ConvergentRefuge[/B][/COLOR]:[COLOR=#5454FF][B]~[/B][/COLOR]$ pwd
/home/sarah
[COLOR=#54FF54][B]sarah@ConvergentRefuge[/B][/COLOR]:[COLOR=#5454FF][B]~[/B][/COLOR]$ sudo blkid
[sudo] password for sarah:  
/dev/sda1: UUID="C7BD-3586" TYPE="vfat" PARTLABEL="EFI System Partition" PARTUUID="9b0d847b-7f50-4ad4-b99e-5562481e05a5"
/dev/sda2: UUID="029c3c88-8edb-4da0-a741-5d912950e2e1" UUID_SUB="4ad04613-a9e6-49d5-a935-2cb939a5ccee" TYPE="btrfs" PARTUUID=
"fc56426c-8241-4db6-9661-24c17f161a18"
/dev/sda3: UUID="79F8D858044BC8BB" TYPE="ntfs" PARTLABEL="Windows" PARTUUID="c16c1189-efcf-4dc1-a23c-289c5773ed42"
/dev/sda4: UUID="183C4E233C4DFC6E" TYPE="ntfs" PARTUUID="0d356e7f-73d9-49bb-88e7-d2d9512552e5"
/dev/sdc1: LABEL="ELYSIUM" UUID="0f834b1e-78a4-4b8b-9528-3b6c3f5ae37b" UUID_SUB="a84c1c8f-8484-404d-b420-777c6b1f0da9" TYPE="
btrfs" PARTLABEL="ELYSIUM" PARTUUID="9cc2500a-68ea-4a2e-ba3d-17464271170d"
/dev/sde1: UUID="2018-07-25-03-28-48-00" LABEL="Kubuntu 18.04.1 LTS amd64" TYPE="iso9660" PTUUID="418c5dc0" PTTYPE="dos" PART
UUID="418c5dc0-01"
/dev/sde2: SEC_TYPE="msdos" UUID="0D5F-1DB6" TYPE="vfat" PARTUUID="418c5dc0-02"
/dev/sdb1: PARTLABEL="Basic data partition" PARTUUID="419dcac7-a187-468d-bf56-d12ef942f963"
/dev/sdd1: PARTUUID="e8c5b11a-01"
[COLOR=#54FF54][B]sarah@ConvergentRefuge[/B][/COLOR]:[COLOR=#5454FF][B]~[/B][/COLOR]$ findmnt -s
TARGET    SOURCE                                    FSTYPE OPTIONS
/         UUID=029c3c88-8edb-4da0-a741-5d912950e2e1 btrfs  defaults,subvol=@
/home     UUID=029c3c88-8edb-4da0-a741-5d912950e2e1 btrfs  defaults,subvol=@home
none      UUID=45f9fe6b-ae81-47c7-bbd7-f9ca4ac66060 swap   sw
/boot/efi UUID=C7BD-3586                            vfat   defaults
/media/sarah/ELYSIUM
        UUID=0f834b1e-78a4-4b8b-9528-3b6c3f5ae37b btrfs  rw,noatime,space_cache,compress=zstd,autodefrag,subvol=EternalFields
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[jlittle]

Thank you for taking the trouble. I don't understand, if those results are in the same session as the failing subvolume create. I keep thinking there must be something screwy somewhere, like an alias, confusing us.

I wonder why you'd want to create a subvolume in your home directory, and why you haven't used sudo. I'm accustomed to always prefacing btrfs commands with sudo; even subvolume list needs sudo.

[oshunluvr]

All reasons aside, this still should be doable. Curious what this shows us:

cat /etc/mtab |grep home

and have you tried creating the subvolume using sudo? Could be some odd permissions issue, but that's not really logical.

[PhysicistSarah]

All reasons aside, this still should be doable. Curious what this shows us:

cat /etc/mtab |grep home

and have you tried creating the subvolume using sudo? Could be some odd permissions issue, but that's not really logical.

Sorry, I was on vacation in Florida before the start of the new school semester. This might not be worth persuing, but I ran the Konsole command anyway:

[FONT=monospace][COLOR=#54FF54][B]sarah@ConvergentRefuge[/B][/COLOR][COLOR=#000000]:[/COLOR][COLOR=#5454FF][B]~/Desktop/Indexing/Indexing Temp[/B][/COLOR][COLOR=#000000]$ cat /etc/mtab |grep home[/COLOR]
/dev/sda2 /[COLOR=#FF5454][B]home[/B][/COLOR][COLOR=#000000] btrfs rw,relatime,space_cache,subvolid=258,subvol=/@[/COLOR][COLOR=#FF5454][B]home[/B][/COLOR][COLOR=#000000] 0 0[/COLOR]
/[COLOR=#FF5454][B]home[/B][/COLOR][COLOR=#000000]/sarah/.Private /[/COLOR][COLOR=#FF5454][B]home[/B][/COLOR][COLOR=#000000]/sarah ecryptfs rw,nosuid,nodev,relatime,ecryptfs_fnek_sig=737970d8c7398e7e,ecryptfs_sig=c5bbfda1f773a1a8,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_un[/COLOR]
link_sigs 0 0
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