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.\" Copyright 2011 Joshua M. Clulow <josh@sysmgr.org>
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.Dd November 4, 2025
.Dt ZFS-JAIL 8
.Os
.
.Sh NAME
.Nm zfs-jail
.Nd attach or detach ZFS filesystem from FreeBSD jail
.Sh SYNOPSIS
.Nm zfs Cm jail
.Ar jailid Ns | Ns Ar jailname
.Ar filesystem
.Nm zfs Cm unjail
.Ar jailid Ns | Ns Ar jailname
.Ar filesystem
.
.Sh DESCRIPTION
The
.Nm
functionality can be used to assign a dataset onto a running
.Fx
system
.Xr jail 4 ,
allowing
.Xr zfs 8
management utilities to be run inside of the
.Xr jail 4 .
.Pp
To allow management of the dataset from within a jail, the
.Sy jailed
property should be set and the required
.Xr devfs.conf 5
entries to expose
.Pa /dev/zfs
device within the jail must be present.
The
.Sy quota
property cannot be changed from within a jail.
.Pp
To use this functionality, the jail needs the
.Sy allow.mount
and
.Sy allow.mount.zfs
parameters set to
.Sy 1
and the
.Sy enforce_statfs
parameter set to a value lower than
.Sy 2 .
.Pp
The subcommands are as follows:
.Bl -tag -width indent
.It Xo
.Cm jail
.Ar jailid Ns | Ns Ar jailname
.Ar filesystem
.Xc
Attach the specified
.Ar filesystem
to the jail identified by JID
.Ar jailid
or name
.Ar jailname .
From now on this file system tree can be managed from within a jail if the
.Sy jailed
property has been set.
.Pp
You cannot attach a jailed dataset's children to another jail.
You can also not attach the root file system
of the jail or any dataset which needs to be mounted before the zfs rc script
is run inside the jail, as it would be attached unmounted until it is
mounted from the rc script inside the jail.
.Pp
After a dataset is attached to a jail and the
.Sy jailed
property is set, a jailed file system cannot be mounted outside the jail,
since the jail administrator might have set the mount point to an unacceptable
value.
.It Xo
.Cm unjail
.Ar jailid Ns | Ns Ar jailname
.Ar filesystem
.Xc
Detaches the specified
.Ar filesystem
from the jail identified by JID
.Ar jailid
or name
.Ar jailname .
.El
.Sh SEE ALSO
.Xr devfs.conf 5 ,
.Xr zfsprops 7 ,
.Xr jail 8
.Sh CAVEATS
The root directory of jail can not be delegated to the jail with this
utility because the jail must be running with a valid root directory.
.Pp
Jails are a
.Fx
feature and are not relevant on other platforms.
See
.Xr jail 8
for more information on managing jails, or
.Xr zfs-zone 8
for the equivalent functionality on Linux.