Defindit Docs and Howto Home

This page last modified: Jun 27 2007
title:Checking logical volumns with e2fsck and hints for smartd
description:How to make a logical volume active and check for bad blocks with fsck (e2fsck), how to run smartd, how to find alternate superblocks.

Table of contents
How to find the backup superblocks
How to fsck (check) a LVM (logical volume)
Hints for using smartd
Alternate vgchange

How to find the backup superblocks

Sometimes when you try to fsck a volume, you get the "bad superblock"
message. You need to try an alternate superblock. To get a list of possible 

dumpe2fs /dev/hda1 | less

I think you are looking for "Backup superblock". 

How to fsck (check) a LVM (logical volume)

You can't fsck a mounted volume, and that applies to LVMs. You have to
boot from some other media, and *not* mount your hard disk
partitions. Additionally, LVMs have to be changed to an active state.

Get the first CD of your install set or your rescue CD. Insert and at
the prompt for which mode to boot enter:

linux rescue

(this applies to Fedora; other distros have alternate "rescue" mode commands")

When asked if the software should search for Linux (Fedora?)
distributions and mount them, answer "No" (skip). 

Your rescue mode should give you a Linux prompt in single user mode.

At the shell prompt, run "lvm"

At the lvm prompt, enter:

vgchange -a y

It should respond that it has activated logical volumes and print the
volumn names (devices, paths).

Quit from lvm (quit).

e2fsck can check for bad blocks, and simultaneously add any bad blocks
to its badblocks table with the -c option. I suggest you also use -v
so that you can see the status of this very slow operation.

e2fsck -cv /dev/VolGroup00/LogVol00

Hints for using smartd

I suggest that you preempt hard drive failures by running the smart
daemon and occasionally checking its status. This is simplified by
running Webmin.

The smartd config file is /etc/smartd.conf and somewhere towards the
top of the file add a line for each physical hard drive. These two
lines are for a normal IDE drive, and a SATA drive:

/dev/hda -a
/dev/sda -a -d ata

The smartd script is /etc/init.d/smartd and it takes the usual
start/stop commands. You can enable smartd on boot by using chkconfig
(or by using the boot configuration section of Webmin).

The command line tool to check the drive status is smartctl. 

smartctl -a /dev/hda 
smartctl -d ata -a /dev/sda

The -a will give you a synopsis of the drive's health. Read or
write errors are bad.

Webmin makes all this easy, and you don't have to remember the commands.

Alternate vgchange

There is a web page that suggests

vgscan | vgchange -a y

However, this doesn't work with Fedora. There are no stand alone
utilities "vgscan" or "vgchange".