[EN] Why is my btrfs disk not mounting?

[Lanzi]

I took the parameters from an ubuntu pgae, but my drive is not mounted autimatically.
If I do it manually it is mounting!

fstab

UUID=4cb0f615-664f-4911-a0a8-3800dddexxxx    /home/h/disk3        btrfs        defaults,subvol=@    0   1

blkid

/dev/sda1: LABEL="disk3" UUID="11cdeb6d-81c1-4767-ae6f-1d26881cxxxx" UUID_SUB="4cb0f615-664f-4911-a0a8-3800dddexxxx" TYPE="btrfs"

[dibl]

Hi Lanzi.  Is that an entire hdd, or only a partition?  I have a 2-drive btrfs filesystem, here is the /etc/fstab line to automatically mount it:

Code: [Select]

UUID=9025bea6-b615-470a-8759-df1b13f63b52     /mnt/DATA            btrfs        device=/dev/sdd,device=/dev/sde,compress=lzo,space_cache,inode_cache   0    0



I wonder if the UUID in /etc/fstab should be the first UUID in your blkid output?

[Lanzi]

an entire disk!

[dibl]

Try using the first UUID in the /etc/fstab mount line -- the one that goes "11cdeb6d-81c1-4767-ae6f-1d26881cxxxx"

[Lanzi]

Ah, sorry, now I see.
I copied the wrong line.
I already tested boths uuids with fstab and unfortunatly I copied only the second.

I tested both UUID, also the frist and the result is the same -> no automount!

SO, I suppose its a problem with the options.

[dibl]

I'm not sure -- your setup looks like others used in examples that I can find around the web.  But clearly you need to mount the btrfs "root" -- the main filesystem itself, which is defined by the first UUID that you have.  I have not made use of subvolumes -- that must be where the trouble is.

[timc]

Well, if his btrfs is defined on an entire disk, then his root is a subvolume. I don't do that (whole disk), but I do have several subvolumes mounted at bootup. I do not think that, in and of itself, is a problem.

Tim

[Lanzi]

Hi guys,
sorry for the delay. had a lot to do this week.

I changed my parameters in fstab to dibls:

compress=lzo,space_cache,inode_cache
and now it works.

I really don't understand what was wrong with the old ones.

So, thanks a lot to everybody involved!


One more question: dibl: what defines your parameter
"device=/dev/sdd,device=/dev/sde"  ?

[dibl]

One more question: dibl: what defines your parameter
"device=/dev/sdd,device=/dev/sde"  ?

When you make a single BTRFS filesystem on multiple disks, that is how you mount it -- you have to use the device IDs in the mount line in /etc/fstab.

[Lanzi]

ah, okay...
I will read about it. Sounds interesting to determine device to discs!

[dibl]

I like the added security of striped data (RAID 0) and mirrored metadata (RAID 1) on a pair of drives.  I do back up my data regularly, but theoretically I can recover from a single drive failure without needing to restore a backup.   (But I hope I never have to test the theory!)