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Linux Raw File system Management

Pretend we have added a new disk to our computer.

The operating system has detected this new disk as device /dev/xvdf.

The following documents the steps we need to take to use this new space.

Partition the device

You may cut the device into separate logical disks.

In my case I want to use the whole disk

sudo fdisk /dev/xvdf
# choose needed settings

Format the partition with a filesystem

We want to use ext4 so we do

sudo mkfs.ext4 /dev/xvdf

 mke2fs 1.42 (29-Nov-2011)
 Filesystem label=
 OS type: Linux
 Block size=4096 (log=2)
 Fragment size=4096 (log=2)
 Stride=0 blocks, Stripe width=0 blocks
 6553600 inodes, 26214400 blocks
 1310720 blocks (5.00%) reserved for the super user
 First data block=0
 Maximum filesystem blocks=4294967296
 800 block groups
 32768 blocks per group, 32768 fragments per group
 8192 inodes per group
 Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624, 11239424, 20480000, 23887872

 Allocating group tables: done
 Writing inode tables: done
 Creating journal (32768 blocks): done
 Writing superblocks and filesystem accounting information: done

Mount and test the new filesystem

sudo mount /dev/xvdf1 /mnt
touch /mnt/testfile
ls /mnt
sudo umount /mnt
ls /mnt
sudo mount /dev/xvdf1 /mnt

Automatically mount partition at system boot

Add an entry into /etc/fstab for new partition.

/dev/xvdf1   /mnt        ext4   defaults        0 0

Remount read-only or read-write

Sometimes live disks and rescue modes mount your partitions for you. In my case the rescue was mounting root partition as read-only, and I needed to remove an entry in /etc/fstab. This command will remount a partition with rw:

mount -o remount,rw /dev/mapper/VolGroup00-LogVol0 /

This allowed me to edit /etc/fstab, remove the bad entry and reboot. The server came back online. We still need to figure out what happened to the disk, try to recover it.

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