Chapter 4. Partitions

The utility parted allows users to:

View the existing partition table
Change the size of existing partitions
Add partitions from free space or additional hard drives

By default, the parted package is included when installing Red Hat Enterprise Linux. To start parted, log in as root and type the command parted /dev/sda at a shell prompt (where /dev/sda is the device name for the drive you want to configure).

If you want to remove or resize a partition, the device on which that partition resides must not be in use. Creating a new partition on a device which is in use—while possible—is not recommended.

For a device to not be in use, none of the partitions on the device can be mounted, and any swap space on the device must not be enabled.

As well, the partition table should not be modified while it is in use because the kernel may not properly recognize the changes. If the partition table does not match the actual state of the mounted partitions, information could be written to the wrong partition, resulting in lost and overwritten data.

The easiest way to achieve this it to boot your system in rescue mode. When prompted to mount the file system, select Skip.

Alternately, if the drive does not contain any partitions in use (system processes that use or lock the file system from being unmounted), you can unmount them with the umount command and turn off all the swap space on the hard drive with the swapoff command.

Table 4.1, “parted commands” contains a list of commonly used parted commands. The sections that follow explain some of these commands and arguments in more detail.

Table 4.1. `parted` commands

Command	Description
`check minor-num`	Perform a simple check of the file system
`cp from to`	Copy file system from one partition to another; `from` and `to` are the minor numbers of the partitions
`help`	Display list of available commands
`mklabel label`	Create a disk label for the partition table
`mkfs minor-num file-system-type`	Create a file system of type `file-system-type`
`mkpart part-type fs-type start-mb end-mb`	Make a partition without creating a new file system
`mkpartfs part-type fs-type start-mb end-mb`	Make a partition and create the specified file system
`move minor-num start-mb end-mb`	Move the partition
`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`
`resize minor-num start-mb end-mb`	Resize the 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`

4.1. Viewing the Partition Table

After starting parted, use the command print to view the partition table. A table similar to the following appears:

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

The first line contains the disk type, manufacturer, model number and interface, and the second line displays the disk label type. The remaining output below the fourth line shows the partition table.

In the partition table, the Minor 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 Type are metadata, free, primary, extended, or logical. The Filesystem is the file system type, which can be any of the following:

ext2
ext3
fat16
fat32
hfs
jfs
linux-swap
ntfs
reiserfs
hp-ufs
sun-ufs
xfs

If a Filesystem of a device shows no value, this means that its file system type is unknown.

The Flags column lists the flags set for the partition. Available flags are boot, root, swap, hidden, raid, lvm, or lba.

Tip

To select a different device without having to restart parted, use the select command followed by the device name (for example, /dev/sda). Doing so allows you to view or configure the partition table of a device.