---
name: "disktab"
section: "5"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["freebsd", "openbsd"]
url: "https://new.carta.tech/disktab"
---

# disktab(5)

disk description file

## NAME

**disktab** – disk description file

## 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 database. Entries in **disktab** consist of a number of colon (‘:’) separated fields. The first entry for each disk gives the names which are known for the disk, separated by “\|” characters. The last name given should be a long name fully identifying the disk.

The following list indicates the normal values stored for each disk entry:

| | | |
| --- | --- | --- |
| **Name** | **Type** | **Description** |
| dt | str | Type of controller (e.g., SMD, ESDI, floppy). |
| 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 (default: ns\*nt). |
| su | num | Number of sectors per unit (default: sc\*nc). |
| se | num | Sector size in bytes (default: |
| ba | num | Block size for partition |
| bd | num | Block size for partition |
| be | num | Block size for partition |
| \[...\] |  |  |
| bp | num | Block size for partition |
| fa | num | Fragment size for partition |
| fd | num | Fragment size for partition |
| fe | num | Fragment size for partition |
| \[...\] |  |  |
| fp | num | Fragment size for partition |
| oa | num | Offset of partition |
| ob | num | Offset of partition |
| oc | num | Offset of partition |
| \[...\] |  |  |
| op | num | Offset of partition |
| pa | num | Size of partition |
| pb | num | Size of partition |
| pc | num | Size of partition |
| \[...\] |  |  |
| pp | num | Size of partition |
| ta | str | Type of partition |
| tb | str | Type of partition |
| tc | str | Type of partition |
| \[...\] |  |  |
| tp | str | Type of partition |

## FILES

- */etc/disktab*

  ## SEE ALSO

[getdiskbyname(3)](/getdiskbyname/3.md), [disklabel(5)](/disklabel/5.md), [disklabel(8)](/disklabel/8.md), [newfs(8)](/newfs/8.md)

## HISTORY

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