---
name: "disktab"
section: "5"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd", "openbsd"]
url: "https://new.carta.tech/disktab"
---

# disktab(5)

disk description file

## NAME

**disktab** – disk description file

## SYNOPSIS

**#include \<disklabel.h\>**

## DESCRIPTION

**Disktab** is a simple database which describes disk geometries and disk partition characteristics. It is used to initialize the disk label on the disk. The format is patterned after the [termcap(5)](/termcap/5.md) terminal data base. Entries in **disktab** consist of a number of \`:'-separated fields. The first field for each entry gives the names by which a disk's entry may be selected, separated by \`\|' characters. The last name given should be a long name fully identifying the disk.

The optional fields for each entry are:

| | | |
| --- | --- | --- |
| **ID** | Type | Description |
| ty | str | Type of disk (e.g. removable, winchester) |
| dt | str | Type of controller (e.g. |
| ns | num | Number of sectors per track |
| nt | num | Number of tracks per cylinder |
| nc | num | Total number of cylinders on the disk |
| sc | num | Number of sectors per cylinder, ns\*nt default |
| su | num | Number of sectors per unit, sc\*nc default |
| se | num | Sector size in bytes, |
| sf | bool | Controller supports bad144-style bad sector forwarding |
| rm | num | Rotation speed, rpm, 3600 default |
| sk | num | Sector skew per track, default 0 |
| cs | num | Sector skew per cylinder, default 0 |
| hs | num | Headswitch time, usec, default 0 |
| ts | num | One-cylinder seek time, usec, default 0 |
| il | num | Sector interleave (n:1), 1 default |
| d\[0-4\] | num | Drive-type-dependent parameters |
| bs | num | Boot block size, default |
| sb | num | Superblock size, default 0 |
| ba | num | Block size for partition \`a' (bytes) |
| bd | num | Block size for partition \`d' (bytes) |
| be | num | Block size for partition \`e' (bytes) |
| bf | num | Block size for partition \`f' (bytes) |
| bg | num | Block size for partition \`g' (bytes) |
| bh | num | Block size for partition \`h' (bytes) |
| fa | num | Fragment size for partition \`a' (bytes) |
| fd | num | Fragment size for partition \`d' (bytes) |
| fe | num | Fragment size for partition \`e' (bytes) |
| ff | num | Fragment size for partition \`f' (bytes) |
| fg | num | Fragment size for partition \`g' (bytes) |
| fh | num | Fragment size for partition \`h' (bytes) |
| oa | num | Offset of partition \`a' in sectors |
| ob | num | Offset of partition \`b' in sectors |
| oc | num | Offset of partition \`c' in sectors |
| od | num | Offset of partition \`d' in sectors |
| oe | num | Offset of partition \`e' in sectors |
| of | num | Offset of partition \`f' in sectors |
| og | num | Offset of partition \`g' in sectors |
| oh | num | Offset of partition \`h' in sectors |
| pa | num | Size of partition \`a' in sectors |
| pb | num | Size of partition \`b' in sectors |
| pc | num | Size of partition \`c' in sectors |
| pd | num | Size of partition \`d' in sectors |
| pe | num | Size of partition \`e' in sectors |
| pf | num | Size of partition \`f' in sectors |
| pg | num | Size of partition \`g' in sectors |
| ph | num | Size of partition \`h' in sectors |
| ta | str | Partition type of partition \`a' |
| tb | str | Partition type of partition \`b' |
| tc | str | Partition type of partition \`c' |
| td | str | Partition type of partition \`d' |
| te | str | Partition type of partition \`e' |
| tf | str | Partition type of partition \`f' |
| tg | str | Partition type of partition \`g' |
| th | str | Partition type of partition \`h' |

## FILES

- */etc/disktab*

  ## SEE ALSO

[getdiskbyname(3)](/getdiskbyname/3.md), [bsdlabel(8)](/bsdlabel/8.md), [newfs(8)](/newfs/8.md)

## HISTORY

The **disktab** description file appeared in 4.2BSD.