Ext3 users - Nov 2015 - Re: recovering corrupt file system

Any recommendations for tools to diagnose and recover problems on an ext4 file
system?

In particular:
root@jessie01:~# mount -o ro /dev/markov02/root /mnt/markov02
mount: wrong fs type, bad option, bad superblock on /dev/mapper/markov02-root,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.
and e2fsck says
root@jessie01:~# e2fsck /dev/markov02/root
e2fsck 1.42.12 (29-Aug-2014)
/dev/markov02/root: recovering journal
Superblock needs_recovery flag is clear, but journal has data.

markov02/root is an LVM volume, built on partitions from 2 disks in a virtual
machine.  The initial symptom was that the VM the disks were in originally would
only get as far as busybox when it started.  However, I think the filesystem was
OK even after that, since it was visible in busybox and in another VM.  I think
virt-manager might have overwritten on of the disks because I left
"allocate entire disk now" checked when I moved one of the disks
between machines.

I'm making copies of the virtual disks now.
Ross Boylan

I guess some of the trouble was that the virtual disk was mounted read-only at
the VM level.  When I mounted read/write I was able to do fsck, which gave
messages about replaying the logs and a couple messages about changing the inode
counts (sorry, don't have the exact words).  Then I ran fsck -f, which
didn't report any problems.  Then I mounted it, and everything seems OK.

I'm still interested in the general question about how to diagnose and
recover from file system errors, since I have another virtual machine that was
backed by a failing real disk.
________________________________________
From: Boylan, Ross
Sent: Wednesday, November 18, 2015 4:35 PM
To: Ext3-users@redhat.com
Subject: recovering corrupt file system

Any recommendations for tools to diagnose and recover problems on an ext4 file
system?

In particular:
root@jessie01:~# mount -o ro /dev/markov02/root /mnt/markov02
mount: wrong fs type, bad option, bad superblock on /dev/mapper/markov02-root,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.
and e2fsck says
root@jessie01:~# e2fsck /dev/markov02/root
e2fsck 1.42.12 (29-Aug-2014)
/dev/markov02/root: recovering journal
Superblock needs_recovery flag is clear, but journal has data.

markov02/root is an LVM volume, built on partitions from 2 disks in a virtual
machine.  The initial symptom was that the VM the disks were in originally would
only get as far as busybox when it started.  However, I think the filesystem was
OK even after that, since it was visible in busybox and in another VM.  I think
virt-manager might have overwritten on of the disks because I left
"allocate entire disk now" checked when I moved one of the disks
between machines.

I'm making copies of the virtual disks now.
Ross Boylan

well, the next place to go, if fsck isn't enough would be to to try
debugfs(1)
man debugfs.

On Wed, Nov 18, 2015 at 8:39 PM, Boylan, Ross <Ross.Boylan@ucsf.edu>
wrote:
> I guess some of the trouble was that the virtual disk was mounted
> read-only at the VM level.  When I mounted read/write I was able to do
> fsck, which gave messages about replaying the logs and a couple messages
> about changing the inode counts (sorry, don't have the exact words). 
Then
> I ran fsck -f, which didn't report any problems.  Then I mounted it,
and
> everything seems OK.
>
> I'm still interested in the general question about how to diagnose and
> recover from file system errors, since I have another virtual machine that
> was backed by a failing real disk.
> ________________________________________
> From: Boylan, Ross
> Sent: Wednesday, November 18, 2015 4:35 PM
> To: Ext3-users@redhat.com
> Subject: recovering corrupt file system
>
> Any recommendations for tools to diagnose and recover problems on an ext4
> file system?
>
> In particular:
> root@jessie01:~# mount -o ro /dev/markov02/root /mnt/markov02
> mount: wrong fs type, bad option, bad superblock on
> /dev/mapper/markov02-root,
>        missing codepage or helper program, or other error
>
>        In some cases useful info is found in syslog - try
>        dmesg | tail or so.
> and e2fsck says
> root@jessie01:~# e2fsck /dev/markov02/root
> e2fsck 1.42.12 (29-Aug-2014)
> /dev/markov02/root: recovering journal
> Superblock needs_recovery flag is clear, but journal has data.
>
> markov02/root is an LVM volume, built on partitions from 2 disks in a
> virtual machine.  The initial symptom was that the VM the disks were in
> originally would only get as far as busybox when it started.  However, I
> think the filesystem was OK even after that, since it was visible in
> busybox and in another VM.  I think virt-manager might have overwritten on
> of the disks because I left "allocate entire disk now" checked
when I moved
> one of the disks between machines.
>
> I'm making copies of the virtual disks now.
> Ross Boylan
>
> _______________________________________________
> Ext3-users mailing list
> Ext3-users@redhat.com
> https://www.redhat.com/mailman/listinfo/ext3-users
>


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