Managing Partions With RHEL 6

Introduction

Most Linux distrobution, which is also the case with RHEL 6, uses the MBR (Master Boot Record) partitioning format. The MBR is designed to hold up to maximum 4 primary partition. If more is needed, you must use one primary as extended partition. And do not forget to let the extended partition use all remaining disk space. After creating an extended partition, you can create logical partition on the extended partiti

Graphical Tool

In a desktop RHEL, there is the graphical tool for managing our partition - palimpsest.

$ yum install gnome-disk-utility

A never GUI tool that is maybe better is parted. The good thing with this tool is that it also can resize and copy partitions.

$ yum install parted

Command Line

At the command line, you have the fdisk tool. When using the fdisk tool always use the following options:

• -c Switch off DOS-compatible mode.
• -u When listing partition tables, give sizes in sectors instead of cylinders.

Lets get started with fdisk and create a new primary partition.

$ fdisk -cu /dev/sda

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): p

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders, total 488397168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x7f3d8c0f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048   205826047   102400000   8e  Linux LVM

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 3
First sector (205826048-488397167, default 205826048): 
Using default value 205826048
Last sector, +sectors or +size{K,M,G} (205826048-488397167, default 488397167): +500M

Command (m for help): p

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders, total 488397168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x7f3d8c0f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048   205826047   102400000   8e  Linux LVM
/dev/sda3       205826048   206850047      512000   83  Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

$ reboot

After reboot you can check your new primary partition.

$ fdisk -cul /dev/sda

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders, total 488397168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x7f3d8c0f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048   205826047   102400000   8e  Linux LVM
/dev/sda3       205826048   206850047      512000   83  Linux

Now lets create an ext4 file system on the new primary partition.

$ mkfs -t ext4 /dev/sda3

And mount it.

$ mkdir /extra
$ mount /dev/sda3 /extra

If you want RHEL to automatically mount your new partition at boot, you need to add that to /etc/fstab. And the recommended way to identify the partition is with it's UUID.

$ blkid /dev/sda3

$ vi /etc/fstab

UUID=b2b97c2f-f0cb-4b41-b297-7f7d36d2efd0 /extra                   ext4    defaults        1 2

And finally save and reboot.