Introduction to different methods........
Many users need to view the existing partition table, change the
size of the partitions, remove partitions, or add partitions from
free space or additional hard drives. The utility parted allows users to perform these tasks. This
chapter discusses how to use parted to
perform file system tasks.
If you want to view the system's disk space usage or monitor the
disk space usage, refer to Section 40.3 File
Systems.
You must have the parted package
installed to use the parted utility. To
start parted, at a shell prompt as root,
type the command parted /dev/sda, where /dev/sda is the device name for the drive you
want to configure. The (parted) prompt is
displayed. Type help to view a list of
available commands.
If you want to create, remove, or resize a partition, the device
cannot be in use (partitions cannot be mounted, and swap space
cannot be enabled). The partition table should not be modified
while in use because the kernel may not properly recognize the
changes. Data could be overwritten by writing to the wrong
partition because the partition table and partitions mounted do not
match. The easiest way to achieve this it to boot your system in
rescue mode. Refer to Chapter 5
Basic System Recovery for instructions on booting into
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
12-1 contains a list of commonly used parted commands. The sections that follow explain
some of them in more detail.
| 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 |
Table 12-1. parted commands
After starting parted, type the
following command to view the partition table:
A table similar to the following appears:
Disk geometry for /dev/sda: 0.000-8678.789 megabytes
Disk label type: msdos
Minor Start End Type Filesystem Flags
1 0.031 101.975 primary ext3 boot
2 101.975 5098.754 primary ext3
3 5098.755 6361.677 primary linux-swap
4 6361.677 8675.727 extended
5 6361.708 7357.895 logical ext3
Disk geometry for /dev/hda: 0.000-9765.492 megabytes
Disk label type: msdos
Minor Start End Type Filesystem Flags
1 0.031 101.975 primary ext3 boot
2 101.975 611.850 primary linux-swap
3 611.851 760.891 primary ext3
4 760.891 9758.232 extended lba
5 760.922 9758.232 logical ext3
|
The first line displays the size of the disk, the second line
displays the disk label type, and the remaining output 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. The Type is one of
primary, extended, or logical. The Filesystem is the file system type, which can be one
of ext2, ext3, fat16, fat32, hfs, jfs, linux-swap, ntfs, reiserfs,
hp-ufs, sun-ufs, or xfs. The Flags column
lists the flags set for the partition. Available flags are boot,
root, swap, hidden, raid, lvm, or lba.
In this example, minor number 1 refers to the /boot/ file system, minor number 2 refers to the
root file system (/), minor number 3
refers to the swap, and minor number 5 refers to the /home/ file system.
 |
Tip |
| |
To select a different device without having to restart
parted, use the select command followed by the device name such as
/dev/sda. Then, you can view its
partition table or configure it.
|
 |
Warning |
| |
Do not attempt to create a partition on a device that is in
use.
|
Before creating a partition, boot into rescue mode (or unmount
any partitions on the device and turn off any swap space on the
device).
Start parted, where /dev/sda is the device on which to create the
partition:
View the current partition table to determine if there is enough
free space:
If there is not enough free space, you can resize an existing
partition. Refer to Section
12.1.4 Resizing a Partition for details.
From the partition table, determine the start and end points of
the new partition and what partition type it should be. You can
only have four primary partitions (with no extended partition) on a
device. If you need more than four partitions, you can have three
primary partitions, one extended partition, and multiple logical
partitions within the extended. For an overview of disk partitions,
refer to the appendix An Introduction to Disk
Partitions in the Red Hat Enterprise Linux
Installation Guide.
For example, to create a primary partition with an ext3 file
system from 1024 megabytes until 2048 megabytes on a hard drive
type the following command:
mkpart primary ext3 1024 2048
|
|
Tip |
| |
If you use the mkpartfs command
instead, the file system is created after the partition is created.
However, parted does not support creating
an ext3 file system. Thus, if you wish to create an ext3 file
system, use mkpart and create the file
system with the mkfs command as described
later. mkpartfs works for file system type
linux-swap.
|
The changes start taking place as soon as you press [Enter], so review the command before executing to
it.
After creating the partition, use the print command to confirm that it is in the partition
table with the correct partition type, file system type, and size.
Also remember the minor number of the new partition so that you can
label it. You should also view the output of
to make sure the kernel recognizes the new partition.
The partition still does not have a file system. Create the file
system:
/sbin/mkfs -t ext3 /dev/sda6
|
|
Warning |
| |
Formatting the partition permanently destroys any data that
currently exists on the partition.
|
Next, give the partition a label. For example, if the new
partition is /dev/sda6 and you want to
label it /work:
By default, the installation program uses the mount point of the
partition as the label to make sure the label is unique. You can
use any label you want.
As root, create the mount point:
As root, edit the /etc/fstab file to
include the new partition. The new line should look similar to the
following:
LABEL=/work /work ext3 defaults 1 2
|
The first column should contain LABEL= followed by the label you gave the
partition. The second column should contain the mount point for the
new partition, and the next column should be the file system type
(for example, ext3 or swap). If you need more information about the
format, read the man page with the command man
fstab.
If the fourth column is the word defaults, the partition is mounted at boot
time. To mount the partition without rebooting, as root, type the
command:
|
Warning |
| |
Do not attempt to remove a partition on a device that is in
use.
|
Before removing a partition, boot into rescue mode (or unmount
any partitions on the device and turn off any swap space on the
device).
Start parted, where /dev/sda is the device on which to remove the
partition:
View the current partition table to determine the minor number
of the partition to remove:
Remove the partition with the command rm. For example, to remove the partition with minor
number 3:
The changes start taking place as soon as you press [Enter], so review the command before committing to
it.
After removing the partition, use the print command to confirm that it is removed from the
partition table. You should also view the output of
to make sure the kernel knows the partition is removed.
The last step is to remove it from the /etc/fstab file. Find the line that declares the
removed partition, and remove it from the file.
|
Warning |
| |
Do not attempt to resize a partition on a device that is in
use.
|
Before resizing a partition, boot into rescue mode (or unmount
any partitions on the device and turn off any swap space on the
device).
Start parted, where /dev/sda is the device on which to resize the
partition:
View the current partition table to determine the minor number
of the partition to resize as well as the start and end points for
the partition:
|
Warning |
| |
The used space of the partition to resize must not be larger
than the new size.
|
To resize the partition, use the resize
command followed by the minor number for the partition, the
starting place in megabytes, and the end place in megabytes. For
example:
After resizing the partition, use the print command to confirm that the partition has been
resized correctly, is the correct partition type, and is the
correct file system type.
After rebooting the system into normal mode, use the command
df to make sure the partition was mounted
and is recognized with the new size.
