[SATLUG] Help with a corrupted file system

Alan Lesmerises alesmerises at satx.rr.com
Wed Jul 29 00:49:55 CDT 2015


I'm hoping someone on the list can provide me with some guidance or 
other suggestions that will help me recover data from a corrupted file 
system.  I have some of the data backed up, but I never expected to need 
to back-up an entire partition.

I have a laptop at work running CentOS 7, configured as a LAMP server 
development platform.  When installing CentOS, I accepted the default 
settings, including the use of LVM with XFS.  On the 500GB hard drive, 
that worked out to 50MB (I think) for /boot, 50GB for /, and the rest 
for /home.

About a week and a half ago, the laptop froze-up, and I had to perform a 
hard reboot.  When it tried to come back up -- nothing. It seems that 
the root partition was pooched, and it would not boot.

I started up the CentOS recovery shell (off the install DVD), and tried 
from there to run a number of diagnostics and repair tools, but it seems 
that the XFS log file was unreadable and xfs_repair couldn't do 
anything.  Everything I found said to mount the messed-up partition so 
the log file could be read and the metadata could be read and changes 
applied to the affected files (presumably to re-build things to where 
they should have been after the last reboot), but that partition won't 
mount.

In order to not screw up any data on the hard drive itself, I made an 
image of the root partition and used that to try to recover my data.

When I try using xfs_repair, it says something like 'the log file is not 
empty; try to mount the partition' so the repairs can be made, but of 
course it won't mount.  The only other option I have is running it with 
the -L option (which clears the log file), but then the entire file 
system comes out as garbage -- the file names are unintelligible, and 
the contents of the files are total junk.

There is only one piece of software that I saw anyone suggest for data 
recovery in this situation called "UFS Explorer", since it seems to be 
able to read even a corrupted XFS partition.

So, here are my questions:

1. Does anyone have any experience with this "UFS Explorer" software?
2. Are there any other software or tools (preferably FOSS) that would 
have similar capabilities?
3. This experience seems to indicate that the Journaling aspect of XFS 
(and the fact that file changes are not immediately written to those 
files) is a bit of a vulnerability, especially for a non-server 
application that might have a higher probability of experiencing 
lock-ups, etc.  Would you agree (yes or no), and why?  In other words, 
should I not use it again when I rebuild my laptop's hard drive (to 
avoid this in the future)?

Any inputs will be welcome.

p.s. -- I apologize if I used the wrong terms for some of these -- I'm 
going from memory of what I did a few days ago.  Hopefully you'll still 
understand what I'm talking about!

Al Lesmerises



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