Fdisk, cfdisk and sfdisk are command line partitioning utilities included by default in all Linux distributions. They provide different interfaces to the same set of functions: while they all can be used interactively, only sfdisk is script-oriented. They support DOS, GPT, SGI and SUN partition tables.
In this tutorial we learn how to manipulate partition tables using fdisk, cfdisk and sfdisk, and explore the differences between these tools.
In this tutorial you will learn:
- How to use fdisk, cfdisk and sfdisk to manipulate partition tables
- How to use sfdisk to dump and restore a partition table
- How to list MBR and GPT partition types identifiers
| Category | Requirements, Conventions or Software Version Used |
|---|---|
| System | Distribution agnostic |
| Software | fdisk/cfdisk/sfdisk |
| Other | Privileged access to your Linux system as root or via the sudo command in order to perform system-wide installation of required packages |
| Conventions | # – requires given linux-commands to be executed with root privileges either directly as a root user or by use of sudo command$ – requires given linux-commands to be executed as a regular non-privileged user |
Using fdisk
The fdisk utility has a dialog-based interface similar to that of gdisk, a tool used to work exclusively on GPT partition tables. We invoke fdisk with the device we want to partition as argument:
$ sudo fdisk /dev/vda
Being dialog-based, fdisk asks us to provide a “command”:
Welcome to fdisk (util-linux 2.38.1). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Device does not contain a recognized partition table. Created a new DOS disklabel with disk identifier 0xa8c57b85. Command (m for help):
Commands are represented by letters. As suggested in the prompt, to obtain the list of the available commands we can use m:
Command (m for help): m Help: DOS (MBR) a toggle a bootable flag b edit nested BSD disklabel c toggle the dos compatibility flag Generic d delete a partition F list free unpartitioned space l list known partition types n add a new partition p print the partition table t change a partition type v verify the partition table i print information about a partition Misc m print this menu u change display/entry units x extra functionality (experts only) Script I load disk layout from sfdisk script file O dump disk layout to sfdisk script file Save & Exit w write table to disk and exit q quit without saving changes Create a new label g create a new empty GPT partition table G create a new empty SGI (IRIX) partition table o create a new empty DOS partition table s create a new empty Sun partition table
Changes performed with fdisk are kept in memory until we explicitly decide to write them to disk, using the w command.
Fdisk usage example
Let’s see an example of how to use fdisk to create a partition table with just one partition. Nowadays, the most used partition tables are GPT and DOS. We can create both very easily with fdisk. To create a GPT partition table, for example, we use the g command:
Command (m for help): g Created a new GPT disklabel (GUID: 13A45576-AEFE-EC40-BEDB-A0E21BA01F26).
To create a partition, instead, we usen, and provide:
- The partition type (primary vs extended – only on DOS partition tables)
- The partition number
- The first sector to use for the partition
- The last sector to use for the partition (more practically, its size)
All parameters have a default value. The default partition number, for example is 1, while the default first sector used for a partition depends on whether it is the first one on the disk (in that case it is created with an offset of 2048 sectors; the first available sector is used for subsequent partitions). The partition size is expressed by using the “+” or “-” symbols and one among the “K”, “M”, “G”, “T” and “P” suffixes, respectively for: Kibibyte, Mebibyte, Gibibyte. Tebibyte and Pebibyte:
Command (m for help): n
Partition number (1-128, default 1):
First sector (2048-41943006, default 2048):
Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-41943006, default 41940991):
By default a partition is assigned the “Linux filesystem” type. This can be changed using the t command (see below).
Using cfdisk
Unlike fdisk, cfdisk provides a curses-based interface, which some may consider more user-friendly. As we did for fdisk, we invoke it passing the block device as argument:
$ sudo cfdisk /dev/vda
If the block device doesn’t contain a valid partition table, cfdisk let us select one:
We can manage partitions from the “main” interface using the appropriate entries in the bottom menu:
To change the partition type, we select it and press the t (or T) key, then choose an entry in the dedicated menu:
Using sfdisk
Unlike its companion utilities, sfdisk is script-oriented, so is typically used to perform operations without expecting the user interaction. sfdisk reads commands and instructions from the standard input. When the standard input is a terminal, it runs in interactive mode:
$ sudo sfdisk /dev/vda Welcome to sfdisk (util-linux 2.38.1). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Checking that no-one is using this disk right now ... OK Disk /dev/vda: 20 GiB, 21474836480 bytes, 41943040 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 sfdisk is going to create a new 'dos' disk label. Use 'label: ' before you define a first partition to override the default. Type 'help' to get more information. >>>
As when using fdisk and cfdisk, changes are written to disk only when explicitly requested, and “DOS” partition tables are used by default; to switch to GPT, we must execute:
>>> label: gpt
The syntax used to create a partition is pretty simple. The input format must include the following fields, separated by a comma, a space or a semicolon:
<start> <size> <type> <bootable>
The “start” parameter is the partition starting point (expressed in sectors or in one of the available formats we saw before), “size” and “type” are, respectively, the size and type of the partition. Finally, the “bootable” parameter is used to mark the partition as bootable, using the “*” symbol.
Let’s see an example. Suppose we are working on a DOS partition table, and we want to create a boot partition of 1GiB. Here is what we would write:
>>> ,1GiB,83,*
Let’s explain. First of all, we omitted to the first field, so the default starting point is used for the partition. In the second field, we wrote “1GiB”: this is the partition size. In the third field we specified the partition type: in this case we used 83, which is the DOS partition table identifier for the “Linux filesystem” type (GPT identifiers are different, as we will see). Finally, in the fourth field, we used “*”, to mark the partition as bootable. Here is the result of the command:
Created a new partition 1 of type 'Linux' and of size 1 GiB. /dev/vda1 : 2048 2099199 (1G) Linux /dev/vda2:
We can now pass information about the next partition or write the partition table to disk, using the “write” command.
sfdisk in “script” mode
As we already said, sfdisk reads instruction from the standard input, therefore, to run in non-interactive mode, we can pass instructions to it directly. We can replicate what we did in the previous example using a shell pipe:
$ echo ",1GiB,83,*" | sudo sfdisk /dev/vda
We could even use a “here string”:
$ sudo sfdisk /dev/vda <<< ",1GiB,83,*"
Notice however, that such commands always “start from scratch”, so they create a new disk label each time (deleting existing partitions), and that when in “script” mode, sfdisk writes changes to disk immediately. What if we want to add a partition to an existing table then? To accomplish such task we use the --append option. To add a partition to an existing table, and assign it all the remaining space on disk, for example, we would run:
$ echo ",," | sudo sfdisk --append /dev/vda
How to create multiple partitions at once? We can use the same technique, separating each instruction with a newline. In the example below we create a GPT partition table and two partitions with a single command:
$ echo -e "label: gpt\n,1GiB\n," | sudo sfdisk /dev/vda
More conveniently, we could use a “here document” construct, which is more readable by us silly human beings:
sudo sfdisk /dev/vda << EOF label: gpt ,1GiB , EOF
Unlike fdisk and cfdisk, sfdisk, by default, doesn’t erase the first sector of a disk when creating a new partition table. To obtain the same behavior of the other two utilities, it must be invoked with the --wipe always option.
Resizing a partition
Until now we saw how to create partitions from scratch. What about shrinking or enlarging an existing partition? Well, it’s a pretty simple operation if you think of it: all we must do is to use the same parameters we used at creation time. The only thing we need, is a way to reference a specific partition. We can do that with the -N option, passing the partition number as argument. In the previous example we created a GPT partition table with two partitions. The first one had a size of 1GiB. To shrink it to 512MiB, we would run:
$ echo ",512MiB" | sudo sfdisk -N 1 /dev/vda
The output of the command reports the old and the current situation:
Old situation: Device Start End Sectors Size Type /dev/vda1 2048 2099199 2097152 1G Linux filesystem /dev/vda2 2099200 41940991 39841792 19G Linux filesystem /dev/vda1: New situation: Disklabel type: gpt Disk identifier: B95D2ECA-1336-6949-89E8-BDC3B493F9A2 Device Start End Sectors Size Type /dev/vda1 2048 1050623 1048576 512M Linux filesystem /dev/vda2 2099200 41940991 39841792 19G Linux filesystem The partition table has been altered. Calling ioctl() to re-read partition table. Syncing disks.
That’s it: instead of specifying the amount of space to subtract or add to the partition, we directly specify its new size. Needless to say, if a filesystem exists on a partition, we need to reduce it before reducing the partition itself.
Dumping and restoring a partition table
We can use sfdisk to dump and restore the partition table of a disk. To perform such action we invoke the utility with the -d option (short for --dump). The configuration is dumped on standard output by default. We may want to redirect it to a file, instead:
$ sudo sfdisk -d /dev/vda > vda_dump.txt
To re-apply the dumped configuration to the disk, we would run:
$ sudo sfdisk /dev/vda < vda_dump.txt
To replicate the partition table on a different disk, we can pipe the output of the command directly to another instance of sfdisk:
$ sudo sfdisk -d /dev/vda | sudo sfdisk /dev/vdb
If we just want to take a look the current partition table, we can invoke sfdisk with the
-l option (--list):
$ sudo sfdisk -l /dev/vda Disk /dev/vda: 20 GiB, 21474836480 bytes, 41943040 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 Disklabel type: gpt Disk identifier: B95D2ECA-1336-6949-89E8-BDC3B493F9A2 Device Start End Sectors Size Type /dev/vda1 2048 2099199 2097152 1G Linux filesystem /dev/vda2 2099200 41940991 39841792 19G Linux filesystem
Partition types
Partition types suggest the purpose of a partition, or the filesystem contained on it. We can list available partition types in different ways, depending on the utility we are using. When using fdisk, for example, we can obtain a list of the available partition types by using l. Hexadecimal identifier are used on DOS partition tables, while GUID are used on GPT. Executing the l command on a GPT partitioned disk, we would obtain the following (truncated) output:
1 EFI System C12A7328-F81F-11D2-BA4B-00A0C93EC93B 2 MBR partition scheme 024DEE41-33E7-11D3-9D69-0008C781F39F 3 Intel Fast Flash D3BFE2DE-3DAF-11DF-BA40-E3A556D89593 4 BIOS boot 21686148-6449-6E6F-744E-656564454649 5 Sony boot partition F4019732-066E-4E12-8273-346C5641494F 6 Lenovo boot partition BFBFAFE7-A34F-448A-9A5B-6213EB736C22 7 PowerPC PReP boot 9E1A2D38-C612-4316-AA26-8B49521E5A8B 8 ONIE boot 7412F7D5-A156-4B13-81DC-867174929325 9 ONIE config D4E6E2CD-4469-46F3-B5CB-1BFF57AFC149 10 Microsoft reserved E3C9E316-0B5C-4DB8-817D-F92DF00215AE 11 Microsoft basic data EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 12 Microsoft LDM metadata 5808C8AA-7E8F-42E0-85D2-E1E90434CFB3 13 Microsoft LDM data AF9B60A0-1431-4F62-BC68-3311714A69AD 14 Windows recovery environment DE94BBA4-06D1-4D40-A16A-BFD50179D6AC 15 IBM General Parallel Fs 37AFFC90-EF7D-4E96-91C3-2D7AE055B174 16 Microsoft Storage Spaces E75CAF8F-F680-4CEE-AFA3-B001E56EFC2D 17 HP-UX data 75894C1E-3AEB-11D3-B7C1-7B03A0000000 18 HP-UX service E2A1E728-32E3-11D6-A682-7B03A0000000 19 Linux swap 0657FD6D-A4AB-43C4-84E5-0933C84B4F4F 20 Linux filesystem 0FC63DAF-8483-4772-8E79-3D69D8477DE4 [...]
On a DOS partitioned disk, the output would be the following:
00 Empty 27 Hidden NTFS Win 82 Linux swap / So c1 DRDOS/sec (FAT- 01 FAT12 39 Plan 9 83 Linux c4 DRDOS/sec (FAT- 02 XENIX root 3c PartitionMagic 84 OS/2 hidden or c6 DRDOS/sec (FAT- 03 XENIX usr 40 Venix 80286 85 Linux extended c7 Syrinx 04 FAT16 <32M 41 PPC PReP Boot 86 NTFS volume set da Non-FS data 05 Extended 42 SFS 87 NTFS volume set db CP/M / CTOS / . 06 FAT16 4d QNX4.x 88 Linux plaintext de Dell Utility 07 HPFS/NTFS/exFAT 4e QNX4.x 2nd part 8e Linux LVM df BootIt 08 AIX 4f QNX4.x 3rd part 93 Amoeba e1 DOS access 09 AIX bootable 50 OnTrack DM 94 Amoeba BBT e3 DOS R/O 0a OS/2 Boot Manag 51 OnTrack DM6 Aux 9f BSD/OS e4 SpeedStor 0b W95 FAT32 52 CP/M a0 IBM Thinkpad hi ea Linux extended 0c W95 FAT32 (LBA) 53 OnTrack DM6 Aux a5 FreeBSD eb BeOS fs 0e W95 FAT16 (LBA) 54 OnTrackDM6 a6 OpenBSD ee GPT 0f W95 Ext'd (LBA) 55 EZ-Drive a7 NeXTSTEP ef EFI (FAT-12/16/ 10 OPUS 56 Golden Bow a8 Darwin UFS f0 Linux/PA-RISC b 11 Hidden FAT12 5c Priam Edisk a9 NetBSD f1 SpeedStor 12 Compaq diagnost 61 SpeedStor ab Darwin boot f4 SpeedStor 14 Hidden FAT16 <3 63 GNU HURD or Sys af HFS / HFS+ f2 DOS secondary 16 Hidden FAT16 64 Novell Netware b7 BSDI fs f8 EBBR protective 17 Hidden HPFS/NTF 65 Novell Netware b8 BSDI swap fb VMware VMFS 18 AST SmartSleep 70 DiskSecure Mult bb Boot Wizard hid fc VMware VMKCORE 1b Hidden W95 FAT3 75 PC/IX bc Acronis FAT32 L fd Linux raid auto 1c Hidden W95 FAT3 80 Old Minix be Solaris boot fe LANstep 1e Hidden W95 FAT1 81 Minix / old Lin bf Solaris ff BBT 24 NEC DOS
To know the available types when using sfdisk, instead, we can use the
-T option, and pass the partition label type as argument to --label. For example, to obtain the list of the partition types for GPT and their GUID, we would run:
$ sfdisk -T --label gpt
A series of alias for partition types exist for convenience. They automatically assume the appropriate value depending on the partition table in use:
| PARTITION TYPE | ALIAS | MBR ID | GPT GUID |
|---|---|---|---|
| linux | L | 83 | 0FC63DAF-8483-4772-8E79-3D69D8477DE4 |
| swap | S | 82 | 0657FD6D-A4AB-43C4-84E5-0933C84B4F4F |
| extended | Ex | 05 | – |
| home | H | – | 933AC7E1-2EB4-4F13-B844-0E14E2AEF915 |
| uefi | U | EF | C12A7328-F81F-11D2-BA4B-00A0C93EC93B |
| raid | R | FD | A19D880F-05FC-4D3B-A006-743F0F84911E |
| lvm | V | 8E | E6D6D379-F507-44C2-A23C-238F2A3DF928 |
Conclusions
In this tutorial we learned how to manipulate partition tables using three similar utilities which comes preinstalled in all Linux distributions: fdisk, cfdisk and sfdisk. The first two are designed to work interactively; the third, sfdisk, is script-oriented.
