Chapter 13. Partitions

Note

For an overview of the advantages and disadvantages to using partitions on block devices, see the following KBase article: https://access.redhat.com/solutions/163853.
With the parted utility, you can:
  • View the existing partition table.
  • Change the size of existing partitions.
  • Add partitions from free space or additional hard drives.
The parted package is installed by default on Red Hat Enterprise Linux 7. To start parted, log in as root and enter the following command: 
# parted /dev/sda
Replace /dev/sda with the device name for the drive to configure.

Manipulating Partitions on Devices in Use

For a device to not be in use, none of the partitions on the device can be mounted, and no swap space on the device can be enabled.
If you want to remove or resize a partition, the device on which that partition resides must not be in use.
It is possible to create a new partition on a device that is in use, but this is not recommended.

Modifying the Partition Table

Modifying the partition table while another partition on the same disk is in use is generally not recommended because the kernel is not able to reread the partition table. As a consequence, changes are not applied to a running system. In the described situation, reboot the system, or use the following command to make the system register new or modified partitions: 
# partx --update --nr partition-number disk
The easiest way to modify disks that are currently in use is:
  1. Boot the system in rescue mode if the partitions on the disk are impossible to unmount, for example in the case of a system disk.
  2. When prompted to mount the file system, select Skip.
If the drive does not contain any partitions in use, that is there are no system processes that use or lock the file system from being unmounted, you can unmount the partitions with the umount command and turn off all the swap space on the hard drive with the swapoff command.
To see commonly used parted commands, see Table 13.1, “parted Commands”.

Important

Do not use the parted utility to create file systems. Use the mkfs tool instead.

Table 13.1. parted Commands

Command Description
help Display list of available commands
mklabel label Create a disk label for the partition table
mkpart part-type [fs-type] start-mb end-mb Make a partition without creating a new file system
name minor-num name Name the partition for Mac and PC98 disklabels only
print Display the partition table
quit Quit parted
rescue start-mb end-mb Rescue a lost partition from start-mb to end-mb
rm minor-num Remove the partition
select device Select a different device to configure
set minor-num flag state Set the flag on a partition; state is either on or off
toggle [NUMBER [FLAG] Toggle the state of FLAG on partition NUMBER
unit UNIT Set the default unit to UNIT

13.1. Viewing the Partition Table

To view the partition table:
  1. Start parted.
  2. Use the following command to view the partition table: 
    (parted) print
A table similar to the following one appears:

Example 13.1. Partition Table

Model: ATA ST3160812AS (scsi)
Disk /dev/sda: 160GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End    Size    Type      File system  Flags
 1      32.3kB  107MB  107MB   primary   ext3         boot
 2      107MB   105GB  105GB   primary   ext3
 3      105GB   107GB  2147MB  primary   linux-swap
 4      107GB   160GB  52.9GB  extended		      root
 5      107GB   133GB  26.2GB  logical   ext3
 6      133GB   133GB  107MB   logical   ext3
 7      133GB   160GB  26.6GB  logical                lvm
Following is the description of the partition table:
  • Model: ATA ST3160812AS (scsi): explains the disk type, manufacturer, model number, and interface.
  • Disk /dev/sda: 160GB: displays the file path to the block device and the storage capacity.
  • Partition Table: msdos: displays the disk label type.
  • In the partition table, Number is the partition number. For example, the partition with minor number 1 corresponds to /dev/sda1. The Start and End values are in megabytes. Valid Types are metadata, free, primary, extended, or logical. The File system is the file system type. The Flags column lists the flags set for the partition. Available flags are boot, root, swap, hidden, raid, lvm, or lba.
The File system in the partition table can be any of the following:
  • ext2
  • ext3
  • fat16
  • fat32
  • hfs
  • jfs
  • linux-swap
  • ntfs
  • reiserfs
  • hp-ufs
  • sun-ufs
  • xfs
If a File system of a device shows no value, this means that its file system type is unknown.

Note

To select a different device without having to restart parted, use the following command and replace /dev/sda with the device you want to select: 
(parted) select /dev/sda
It allows you to view or configure the partition table of a device.