--- name: "disklabel" section: "8" platform: "freebsd" package: "base" version: "16.0-CURRENT-20261027-61c70dc16a79" release: "FreeBSD 16.0-CURRENT (2026-10-27)" platforms: ["freebsd", "openbsd", "macos"] url: "https://new.carta.tech/bsdlabel" --- # disklabel(8) read and write BSD label Part of [bsdlabel(8)](/bsdlabel/8.md). ## NAME **bsdlabel** – read and write BSD label ## SYNOPSIS **bsdlabel** \[**-A**\] *disk* \| **-f** *file* **bsdlabel** **-w** \[**-An**\] \[**-B** \[**-b** *boot*\]\] \[**-m** *machine*\] *disk* \| **-f** *file* \[*type*\] **bsdlabel** **-e** \[**-An**\] \[**-B** \[**-b** *boot*\]\] \[**-m** *machine*\] *disk* \| **-f** *file* **bsdlabel** **-R** \[**-An**\] \[**-B** \[**-b** *boot*\]\] \[**-m** *machine*\] \[**-f**\] *disk* \| **-f** *file* *protofile* ## DEPRECATION NOTICE **bsdlabel** is deprecated and is not available in FreeBSD 16.0 or later. Use [gpart(8)](/gpart/8.md) instead( with the **BSD** partitioning scheme), or install the *freebsd-bsdlabel* port or package. ## DESCRIPTION The **bsdlabel** utility installs, examines or modifies the BSD label on a disk partition, or on a file containing a partition image. In addition, **bsdlabel** can install bootstrap code. ### Disk Device Name When specifying the device (i.e., when the **-f** option is not used), the */dev/* path prefix may be omitted; the **bsdlabel** utility will automatically prepend it. ### General Options The **-A** option enables processing of the historical parts of the BSD label. If the option is not given, suitable values are set for these fields. The **-f** option tells **bsdlabel** that the program will operate on a file instead of a disk partition. The **-n** option stops the **bsdlabel** program right before the disk would have been modified, and displays the result instead of writing it. The **-m** *machine* argument forces **bsdlabel** to use a layout suitable for a different architecture. Current valid values are **i386** and **amd64**. If this option is omitted, **bsdlabel** will use a layout suitable for the current machine. ### Reading the Disk Label To examine the label on a disk drive, use the form **bsdlabel** \[**-A**\] \[**-m** *machine*\] *disk* *disk* represents the disk in question, and may be in the form *da0* or */dev/da0*. It will display the partition layout. ### Writing a Standard Label To write a standard label, use the form **bsdlabel** **-w** \[**-An**\] \[**-m** *machine*\] *disk* \[*type*\] If the drive *type* is specified, the entry of that name in the [disktab(5)](/disktab/5.md) file is used; otherwise, or if the type is specified as 'auto', a default layout is used. ### Editing an Existing Disk Label To edit an existing disk label, use the form **bsdlabel** **-e** \[**-An**\] \[**-m** *machine*\] *disk* This command opens the disk label in the default editor, and when the editor exits, the label is validated and if OK written to disk. ### Restoring a Disk Label From a File To restore a disk label from a file, use the form **bsdlabel** **-R** \[**-An**\] \[**-m** *machine*\] *disk* *protofile* The **bsdlabel** utility is capable of restoring a disk label that was previously saved in a file in ASCII format. The prototype file used to create the label should be in the same format as that produced when reading or editing a label. Comments are delimited by ‘#’ and newline. ### Installing Bootstraps If the **-B** option is specified, bootstrap code will be read from the file */boot/boot* and written to the disk. The **-b** *boot* option allows a different file to be used. ## FILES - */boot/boot* Default boot image. - */etc/disktab* Disk description file. ## SAVED FILE FORMAT The **bsdlabel** utility uses an ASCII version of the label when examining, editing, or restoring a disk label. The format is: ``` 8 partitions: # size offset fstype [fsize bsize bps/cpg] a: 81920 16 4.2BSD 2048 16384 5128 b: 1091994 81936 swap c: 1173930 0 unused 0 0 # "raw" part, don't edit ``` If the **-A** option is specified, the format is: ``` # /dev/da1c: type: SCSI disk: da0s1 label: flags: bytes/sector: 512 sectors/track: 51 tracks/cylinder: 19 sectors/cylinder: 969 cylinders: 1211 sectors/unit: 1173930 rpm: 3600 interleave: 1 trackskew: 0 cylinderskew: 0 headswitch: 0 # milliseconds track-to-track seek: 0 # milliseconds drivedata: 0 8 partitions: # size offset fstype [fsize bsize bps/cpg] a: 81920 16 4.2BSD 1024 8192 16 b: 160000 81936 swap c: 1173930 0 unused 0 0 # "raw" part, don't edit ``` Lines starting with a ‘#’ mark are comments. The partition table can have up to 8 entries. It contains the following information: - *#* The partition identifier is a single letter in the range ‘a’ to ‘h’. By convention, partition ‘c’ is reserved to describe the entire disk. - *size* The size of the partition in sectors, **K** (kilobytes - 1024), **M** (megabytes - 1024\*1024), **G** (gigabytes - 1024\*1024\*1024), **%** (percentage of free space *after* removing any fixed-size partitions other than partition ‘c’), or **\*** (all remaining free space *after* fixed-size and percentage partitions). For partition ‘c’, a size of **\*** indicates the entire disk. Lowercase versions of suffixes **K**, **M**, and **G** are allowed. Size and suffix should be specified without any spaces between them. Example: 2097152, 1G, 1024M and 1048576K are all the same size (assuming 512-byte sectors). - *offset* The offset of the start of the partition from the beginning of the drive in sectors, or **\*** to have **bsdlabel** calculate the correct offset to use (the end of the previous partition plus one, ignoring partition ‘c’). For partition ‘c’, **\*** will be interpreted as an offset of 0. The first partition should start at offset 16, because the first 16 sectors are reserved for metadata. - *fstype* Describes the purpose of the partition. The above example shows all currently used partition types. For UFS file systems and [ccd(4)](/ccd/4.md) partitions, use type **4.2BSD**. Other common types are **swap** and **unused**. By convention, partition ‘c’ represents the entire slice and should be of type **unused**, though **bsdlabel** does not enforce this convention. The **bsdlabel** utility also knows about a number of other partition types, none of which are in current use. (See the definitions starting with FS\_UNUSED in ⟨sys/disklabel.h⟩ for more details.) - *fsize* For **4.2BSD** file systems only, the fragment size; see [newfs(8)](/newfs/8.md). - *bsize* For **4.2BSD** file systems only, the block size; see [newfs(8)](/newfs/8.md). - *bps/cpg* For **4.2BSD** file systems, the number of cylinders in a cylinder group; see [newfs(8)](/newfs/8.md). ## EXAMPLES Display the label for the first slice of the *da0* disk, as obtained via */dev/da0s1*: ``` bsdlabel da0s1 ``` Save the in-core label for *da0s1* into the file *savedlabel*. This file can be used with the **-R** option to restore the label at a later date: ``` bsdlabel da0s1 > savedlabel ``` Create a label for *da0s1*: ``` bsdlabel -w /dev/da0s1 ``` Read the label for *da0s1*, edit it, and install the result: ``` bsdlabel -e da0s1 ``` Read the on-disk label for *da0s1*, edit it, and display what the new label would be (in sectors). It does *not* install the new label either in-core or on-disk: ``` bsdlabel -e -n da0s1 ``` Write a default label on *da0s1*. Use another **bsdlabel** **-e** command to edit the partitioning and file system information: ``` bsdlabel -w da0s1 ``` Restore the on-disk and in-core label for *da0s1* from information in *savedlabel*: ``` bsdlabel -R da0s1 savedlabel ``` Display what the label would be for *da0s1* using the partition layout in *label\_layout*. This is useful for determining how much space would be allotted for various partitions with a labeling scheme using **%**-based or **\*** partition sizes: ``` bsdlabel -R -n da0s1 label_layout ``` Install a new bootstrap on *da0s1*. The boot code comes from */boot/boot*: ``` bsdlabel -B da0s1 ``` Install a new label and bootstrap. The bootstrap code comes from the file *newboot* in the current working directory: ``` bsdlabel -w -B -b newboot /dev/da0s1 ``` Completely wipe any prior information on the disk, creating a new bootable disk with a DOS partition table containing one slice, covering the whole disk. Initialize the label on this slice, then edit it. The [dd(1)](/dd/1.md) commands are optional, but may be necessary for some BIOSes to properly recognize the disk: ``` dd if=/dev/zero of=/dev/da0 bs=512 count=32 gpart create -s MBR da0 gpart add -t freebsd da0 gpart set -a active -i 1 da0 gpart bootcode -b /boot/mbr da0 dd if=/dev/zero of=/dev/da0s1 bs=512 count=32 bsdlabel -w -B da0s1 bsdlabel -e da0s1 ``` This is an example disk label that uses some of the new partition size types such as **%**, **M**, **G**, and **\***, which could be used as a source file for “bsdlabel -R ada0s1 new\_label\_file”: ``` # /dev/ada0s1: 8 partitions: # size offset fstype [fsize bsize bps/cpg] a: 400M 16 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*) b: 1G * swap c: * * unused e: 204800 * 4.2BSD f: 5g * 4.2BSD g: * * 4.2BSD ``` ## DIAGNOSTICS The kernel device drivers will not allow the size of a disk partition to be decreased or the offset of a partition to be changed while it is open. ## COMPATIBILITY Due to the use of an *uint32\_t* to store the number of sectors, BSD labels are restricted to a maximum of 2^32-1 sectors. This usually means 2TB of disk space. Larger disks should be partitioned using another method such as [gpart(8)](/gpart/8.md). The various BSDs all use slightly different versions of BSD labels and are not generally compatible. ## SEE ALSO [ccd(4)](/ccd/4.md), [geom(4)](/geom/4.md), [md(4)](/md/4.md), [disktab(5)](/disktab/5.md), [boot0cfg(8)](/boot0cfg/8.md), [gpart(8)](/gpart/8.md), [newfs(8)](/newfs/8.md) ## HISTORY The **disklabel** utility appeared in 4.3BSD-Tahoe. ## BUGS The disklabel scheme supports up to 20 partitions, but **bsdlabel** supports only 8 partitions.