---
name: "nullfs"
section: "4"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/nullfs"
---

# nullfs(4)

null file system

## NAME

**nullfs** – null file system

## SYNOPSIS

To enable support for this driver, place the following line in the kernel configuration file:

**options NULLFS**

Alternatively, to load the driver as a module at boot time, place the following line in [loader.conf(5)](/loader.conf/5.md):

```
nullfs_load="YES"
```

## DESCRIPTION

The **nullfs** driver will permit the FreeBSD kernel to mount a loopback file system sub-tree.

## EXAMPLES

To mount a **nullfs** file system:

```
mount_nullfs /usr/ports /home/devel/ports
```

It is also possible to define an entry in [fstab(5)](/fstab/5.md) that looks similar to:

```
/usr/ports	/home/devel/ports	nullfs		rw	0	0
```

## SEE ALSO

[fstab(5)](/fstab/5.md), [mount\_nullfs(8)](/mount_nullfs/8.md)

## HISTORY

The **nullfs** layer first appeared in 4.4BSD.

## AUTHORS

The **nullfs** kernel implementation was written by John Heideman.

This manual page was written by Daniel Gerzo ⟨*danger@FreeBSD.org*⟩.