File System in Linux

File system is a formated partition on a hard disk

It contains 2 things

• User Data : Most of the space is used by user`s data

• Metadata : Metadata describes the structure of the file system. Most common metadata structure are superblock, inode and directories

Superblock

superblock, which contains information about file system such as:

• File system type

• Size

• Status

• Information about other metadata structures

Due to filesystem failure:

• File system will refuse to mount

• Entire system get hangs

• Even if filesystem mount operation result into success, users may notice strange behavior when mounted such as system reboot, gibberish characters in directory listings etc

To repair file system

e2fsck -f /dev/sda3

Where,

• -f : Force checking even if the file system seems clean.

If super block is not found

dumpe2fs /dev/sda3|grep -i superblock

To repair file system by alternative-superblock use command as follows:
# e2fsck -f -b 8193 /dev/sda3

However it is highly recommended that you make backup before you run fsck command on system, use dd command to create a backup (provided that you have spare space under /disk2)


# dd if=/dev/sda2 of=/disk2/backup-sda2.img