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data corruption

Q. I'd like to share iSCSI storage with our 3 node web server cluster. How can multiple systems access a single iSCSI LUN under Linux operating system? Can I connect multiple servers to a single iSCSI LUN?
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Q. Can I run fsck or e2fsck command when Linux file system is mounted? Do you advice to run fsck on a live file system? I am using Cent OS.

A. No. Do not run fsck on a live or mounted file system. fsck is used to check and optionally repair one or more Linux file systems. Running fsck on a mounted filesystem can usually result in disk / data corruption. So please do not do it. You have two choices
(a) Take down system to single user mode and unmout system

(b) Boot from the installation CD into rescue mode

(a) Take down system to single user mode and unmout system

Following are steps :
=> Use init (process control initialization ) command to change runlevel 1 (singe user mode)
=> Use umount command to unmount /home file system
=> Run fsck using fsck command

Let us say you would like to run fsck on /home (/dev/sda3):

# init 1
# umount /home
# umount /dev/sda

# fsck /homeOR
# fsck /dev/sda3OR
# e2fsck -y /dev/sda3

(b) Boot from the installation CD into rescue mode

If you are using Cent OS/Fedora Core/RHEL linux, boot from first CD and at boot prompt type linux rescue nomount:
boot: linux rescue nomount

Now make new node for disk and partition 3:
# mknod /dev/sda
# mknod /dev/sda3
# fsck /dev/sda3

OR
# e2fsck -y /dev/sda3

Don't forget to reboot the system:
# exit;exit
# reboot