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NULLFS(5) File Formats Manual NULLFS(5)

nullfsnull file system

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):


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

To mount a nullfs file system:

mount_nullfs /usr/ports /home/devel/ports

fstab(5), mount_nullfs(8)

The nullfs layer first appeared in 4.4BSD.

The nullfs kernel implementation was written by John Heideman.

This manual page was written by Daniel Gerzo <>.

February 10, 2015 FreeBSD-11.1