Ubunutu scanning for a btrfs fs it will never find

Ubunutu scanning for a btrfs fs it will never find

[Antonio Rodulfo]

Dear fellows,

After upgrading one of my laptops from XUbuntu 12.04 to 12.10, I started to
see a "Scanning for Btrfs filesystems" message after the initial grub menu
and before the system issues its startup sequence of messages.

The first time I saw the message, my laptop completely stopped after
issuing some error message, claiming it wasn't able to start any system. I
restarted the system and opted for a former startup option, which worked
fine; restarted the system and opted for a WXP startup (I happen to need
this monster installed too), which worked fine; to my surprise, the next
restart with the newest kernel & version of XUbuntu worked fine as well.

The system hangs now there for several seconds (15, maybe?) and keeps going
with no further reference to btrfs.

I don't have any btrfs in my laptop nor plan to have it. Since it has
already showed fatal errors, I'd like to get rid of it.

I have read I could remove btrfs-tools module from my kernel and / or
blacklist it in /etc/modprobe.d

What do you recommend?

--
Kind regards,

Antonio Rodulfo
Industrial Engineer, Development Engineer and Project Consultant

Re: Ubunutu scanning for a btrfs fs it will never find

[Duncan]

Antonio Rodulfo posted on Sun, 17 Nov 2013 13:21:35 +0100 as excerpted:

> After upgrading one of my laptops from XUbuntu 12.04 to 12.10, I started
> to see a "Scanning for Btrfs filesystems" message after the initial grub
> menu and before the system issues its startup sequence of messages.

> The system hangs now there for several seconds (15, maybe?) and keeps
> going with no further reference to btrfs.
> 
> I don't have any btrfs in my laptop nor plan to have it.

> I have read I could remove btrfs-tools module from my kernel and / or
> blacklist it in /etc/modprobe.d
> 
> What do you recommend?

I'm not really familiar with xubuntu (or indeed, ubuntu at all), but an 
educated guess based on your description is that 12.10 has a btrfs 
option, possibly even the default, if installed "clean", thus the 
scanning for btrfs (which from your description is coming from the pre-
packaged initramfs/initrd before root is even mounted).

Since you upgraded and apparently kept the existing partitioning and 
filesystems without btrfs, you don't have any btrfs for it to find, so 
all it does is delay your boot.

Yes, it should be possible to turn off that scan, but because it appears 
to be coming from the pre-built initr* that's shipped by the distro with 
the assumption that new installs will likely have btrfs, turning it off 
may be a bit complex, possibly involving an initr* rebuild, tho it's also 
possible the distro has an alternative initr* available without that 
scan, exactly because of situations like yours, and all you need to do is 
install that alternative.

However, that's a distro-specific issue, so chances are you'll need to 
post the question to your distro's lists or forums (unless someone here 
by simple chance happens to have distro-specific knowledge of (x)ubuntu 
and can post an answer).  I don't know whether that'd be xubuntu 
specifically, or the general ubuntu forums/lists, but that's where I'd 
suggest you post the question if nobody chances to have a good answer for 
you here.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

Re: Ubunutu scanning for a btrfs fs it will never find

[Chris Murphy]

Antonio Rodulfo posted on Sun, 17 Nov 2013 13:21:35 +0100 as excerpted:

> After upgrading one of my laptops from XUbuntu 12.04 to 12.10, I started
> to see a "Scanning for Btrfs filesystems" message after the initial grub
> menu and before the system issues its startup sequence of messages.

> The system hangs now there for several seconds (15, maybe?) and keeps
> going with no further reference to btrfs.

If none of your physical disks has ever had Btrfs on it, I'd say it's a bug and should be reported.

If the disk ever once had a Btrfs volume, then it might be a stale Btrfs superblock has been found and whatever is scanning found it's broken and is looking for others, and then times out. But I'd still say this should be rather fast, that it isn't also indicates a bug.


> I have read I could remove btrfs-tools module from my kernel and / or
> blacklist it in /etc/modprobe.d

OK if this is easiest for you fine, but I still think there's at least one bug somewhere and you shouldn't have to do this.


Chris Murphy