---
name: "fsirand"
section: "8"
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/fsirand"
---

# fsirand(8)

randomize inode generation numbers

## NAME

**fsirand** – randomize inode generation numbers

## SYNOPSIS

**fsirand** \[**-bfp**\] *special* *...*

## DESCRIPTION

The **fsirand** command installs random generation numbers on all the inodes for each filesystem specified on the command line by *special*. This increases the security of NFS-exported filesystems by making it difficult to “guess” filehandles.

*Note*: [newfs(8)](/newfs/8.md) now does the equivalent of **fsirand** itself so it is no longer necessary to run **fsirand** by hand on a new filesystem. It is only used to re-randomize or report on an existing filesystem.

**fsirand** should only be used on an unmounted filesystem that has been checked with [fsck(8)](/fsck/8.md) or a filesystem that is mounted read-only. **fsirand** may be used on the root filesystem in single-user mode but the system should be rebooted via “reboot -n” afterwards.

The options are as follows:

- **-b**

  Use the default block size (usually 512 bytes) instead of the value gleaned from the disklabel.

- **-f**

  Force **fsirand** to run even if the filesystem on *special* is not marked as clean.

- **-p**

  Print the current generation numbers for all inodes instead of generating new ones.

## SEE ALSO

[fs(5)](/fs/5.md), [fsck(8)](/fsck/8.md), [newfs(8)](/newfs/8.md), [reboot(8)](/reboot/8.md)

## HISTORY

The **fsirand** command appeared in SunOS 3.x. This version of **fsirand** first appeared in OpenBSD 2.1.

## AUTHORS

Todd C. Miller

## CAVEATS

Since **fsirand** allocates enough memory to hold all the inodes in a given cylinder group, it may use a large amount of memory for large disks with few cylinder groups.