Difference between revisions of "Fdisk"

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(Fix broken link to gdisk package (now points to gptfdisk, it's replacement))
(Added Wikipedia link to "curses".)
 
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This article covers {{man|8|fdisk}} and its related {{man|8|sfdisk}} utility.
 
This article covers {{man|8|fdisk}} and its related {{man|8|sfdisk}} utility.
  
{{Note|1=''fdisk'' supports [[GPT]] since {{Pkg|util-linux}} 2.23. [https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/?id=766d5156c43b784700d28d1c1141008b2bf35ed7] Alternatively, {{Pkg|gptfdisk}}}} may be used; see [[gdisk]] for more information.}}
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{{Note|1=''fdisk'' supports [[GPT]] since {{Pkg|util-linux}} 2.23. [https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/?id=766d5156c43b784700d28d1c1141008b2bf35ed7] Alternatively, {{Pkg|gptfdisk}} may be used; see [[gdisk]] for more information.}}
  
{{Tip|For basic partitioning functionality with a text user interface, {{man|8|cfdisk}} can be used.}}
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{{Tip|For basic partitioning functionality with a [[Wikipedia:curses (programming library)|curses]]-based user interface, {{man|8|cfdisk}} can be used.}}
  
 
== Installation ==
 
== Installation ==
  
To use ''fdisk'' and its associated utilities, the {{pkg|util-linux}} package, which is part of the {{grp|base}} group is required.
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To use ''fdisk'' and its associated utilities, the {{pkg|util-linux}} package, which is part of the {{grp|base}} group, is required.
  
 
== List partitions ==
 
== List partitions ==
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Write the table to disk and exit via the {{ic|w}} command.
 
Write the table to disk and exit via the {{ic|w}} command.
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== Moving partitions ==
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{{Warning|Partitions can only be moved while offline. Because moving a partition requires the whole partition to be rewritten on disk, it is a slow and potentially hazardous operation. Backups are strongly recommended! According to the ''sfdisk'' man page, "this operation is risky and not atomic."}}
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In order to move a partition, you need to have free space available where the partition will be moved. If necessary, you can make room by shrinking your partitions and the filesystems on them. See [[Parted#Shrinking partitions]]. To relocate a partition:
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# echo '+''sectors'',' | sfdisk --move-data ''device'' -N ''number''
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Where {{ic|''sectors''}} is the number of sectors to move the partition (the {{ic|''+''}} indicates moving it forward), {{ic|''device''}} is the device that holds the partition, and {{ic|''number''}} is the partition number. Note that if you add a new partition in the middle or at the beginning of your disk, you will likely want to renumber the partitions. See [[#Sort partitions]] or the "extra functionality" mode of ''fdisk''.
  
 
== Tips and tricks ==
 
== Tips and tricks ==

Latest revision as of 18:17, 4 June 2019

util-linux fdisk is a dialogue-driven command-line utility that creates and manipulates partition tables and partitions on a hard disk. Hard disks are divided into partitions and this division is described in the partition table.

This article covers fdisk(8) and its related sfdisk(8) utility.

Note: fdisk supports GPT since util-linux 2.23. [1] Alternatively, gptfdisk may be used; see gdisk for more information.
Tip: For basic partitioning functionality with a curses-based user interface, cfdisk(8) can be used.

Installation

To use fdisk and its associated utilities, the util-linux package, which is part of the base group, is required.

List partitions

To list partition tables and partitions on a device, you can run the following, where device is a name like /dev/sda:

# fdisk -l /dev/sda
Note: If the device is not specified, fdisk will list all partitions in /proc/partitions.

Backup and restore partition table

Before making changes to a hard disk, you may want to backup the partition table and partition scheme of the drive. You can also use a backup to copy the same partition layout to numerous drives.

For both GPT and MBR you can use sfdisk to save the partition layout of your device to a file with the -d/--dump option. Run the following command for device /dev/sda:

# sfdisk -d /dev/sda > sda.dump

The file should look something like this for a single ext4 partition that is 1 GiB in size:

sda.dump
label: gpt
label-id: AAAAAAAA-BBBB-CCCC-DDDD-EEEEEEEEEEEE
device: /dev/sda
unit: sectors
first-lba: 34
last-lba: 1048576

/dev/sda1 : start=2048, size=1048576, type=0FC63DAF-8483-4772-8E79-3D69D8477DE4, uuid=BBF1CD36-9262-463E-A4FB-81E32C12BDE7

To later restore this layout you can run:

# sfdisk /dev/sda < sda.dump

Create a partition table and partitions

The first step to partitioning a disk is making a partition table. After that, the actual partitions are created according to the desired partition scheme. See the partition table article to help decide whether to use MBR or GPT.

Before beginning, you may wish to backup your current partition table and scheme.

Recent versions of fdisk have abandoned the deprecated system of using cylinders as the default display unit, as well as MS-DOS compatibility by default. fdisk automatically aligns all partitions to 2048 sectors, or 1 MiB, which should work for all EBS sizes that are known to be used by SSD manufacturers. This means that the default settings will give you proper alignment.

Start fdisk against your drive as root. In this example we are using /dev/sda:

# fdisk /dev/sda

This opens the fdisk dialogue where you can type in commands.

Create new table

Warning: If you create a new partition table on a disk with data on it, it will erase all the data on the disk. Make sure this is what you want to do.

To create a new partition table and clear all current partition data type o at the prompt for a MBR partition table or g for a GUID Partition Table (GPT). Skip this step if the table you require has already been created.

Create partitions

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: Place each step into a subsection. (Discuss in Talk:Fdisk#)

Create a new partition with the n command. You enter a partition type, partition number, starting sector, and an ending sector.

When prompted, specify the partition type, type p to create a primary partition or e to create an extended one. There may be up to four primary partitions.

The first sector must be specified in absolute terms using sector numbers. The last sector can be specified using the absolute position in sectors or using the + symbol to specify a position relative to the start sector measured in sectors, kibibytes (K), mebibytes (M), gibibytes (G), tebibytes (T), or pebibytes (P); for instance, setting +2G as the last sector will specify a point 2GiB after the start sector. Pressing the Enter key with no input specifies the default value, which is the start of the largest available block for the start sector and the end of the same block for the end sector.

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: Suggest using Discoverable Partitions. (Discuss in Talk:Fdisk#)

Select the partition's type id. The default, Linux filesystem, should be fine for most use. Press l to show the codes list. You can make the partition bootable by typing a.

Tip:
  • When partitioning it is always a good idea to follow the default values for first and last partition sectors. Additionally, specify partition sizes with the +<size>{M,G,...} notation. Such partitions are always aligned according to the device properties.
  • On a disk with a MBR partition table leave at least 33 512-byte sectors (16.5 KiB) of free unpartitioned space at the end of the disk to allow converting between MBR and GPT.
  • EFI system partition requires type EFI System.
  • GRUB requires a BIOS boot partition with type BIOS boot when installing GRUB to a disk.
  • It is recommended to use Linux swap for any swap partitions, since systemd will automount it.

See the respective articles for considerations concerning the size and location of these partitions.

Repeat this procedure until you have the partitions you desire.

Write changes to disk

Write the table to disk and exit via the w command.

Moving partitions

Warning: Partitions can only be moved while offline. Because moving a partition requires the whole partition to be rewritten on disk, it is a slow and potentially hazardous operation. Backups are strongly recommended! According to the sfdisk man page, "this operation is risky and not atomic."

In order to move a partition, you need to have free space available where the partition will be moved. If necessary, you can make room by shrinking your partitions and the filesystems on them. See Parted#Shrinking partitions. To relocate a partition:

# echo '+sectors,' | sfdisk --move-data device -N number

Where sectors is the number of sectors to move the partition (the + indicates moving it forward), device is the device that holds the partition, and number is the partition number. Note that if you add a new partition in the middle or at the beginning of your disk, you will likely want to renumber the partitions. See #Sort partitions or the "extra functionality" mode of fdisk.

Tips and tricks

Sort partitions

This applies for when a new partition is created in the space between two partitions or a partition is deleted. /dev/sda is used in this example.

# sfdisk -r /dev/sda

After sorting the partitions if you are not using Persistent block device naming, it might be required to adjust the /etc/fstab and/or the /etc/crypttab configuration files.

Note: The kernel must read the new partition table for the partitions (e.g. /dev/sda1) to be usable. Reboot the system or tell the kernel to reread the partition table.

See also