BECTL(8) FreeBSD System Manager's Manual BECTL(8)
NAME
bectl - manage ZFS boot environments
SYNOPSIS
bectl [-h]
bectl [-r beroot] activate [-t | -T] beName
bectl [-r beroot] check
bectl [-r beroot] create [-r] [-e {nonActiveBe | beName@snapshot}]
newBeName
bectl [-r beroot] create [-r] beName@snapshot
bectl [-r beroot] create -E newBeName
bectl [-r beroot] destroy [-Fo] beName[@snapshot]
bectl [-r beroot] export sourceBe
bectl [-r beroot] import targetBe
bectl [-r beroot] jail [-bU] [{-o key=value | -u key}]... beName
[utility [argument ...]]
bectl [-r beroot] list [-aDHs] [-c property] [-C property]
[{-c property | -C property}]
bectl [-r beroot] mount beName [mountpoint]
bectl [-r beroot] rename origBeName newBeName
bectl [-r beroot] {ujail | unjail} {jailId | jailName | beName}
bectl [-r beroot] {umount | unmount} [-f] beName
DESCRIPTION
The bectl utility manages bootable ZFS clones called boot environments.
Boot environments allow system changes to be tested safely, as they are
selectable directly from the boot loader(8). This utility can create,
list, mount, or jail boot environments. Once the changes have been
tested, the boot environment can be unmounted, activated, renamed, and
destroyed.
Supported Subcommands and Flags
-h Print usage information and exit.
-r beroot subcommand
Specify a parent dataset for the boot environment to use for
subcommand for operation on manually imported pools or unusual
layouts.
activate [-t | -T] beName
Activate the given beName as the default boot filesystem. If the
-t flag is given, this takes effect only for the next boot. Flag
-T removes temporary boot once configuration. Without temporary
configuration, the next boot will use zfs dataset specified in
boot pool bootfs property.
check Perform a check to see if the current system can use boot
environments. If boot environments are supported and used, bectl
will exit with a status code of 0. Any other status code is not
currently defined and may, in the future, grow special meaning
for different degrees of sanity check failures.
create [-r] [-e {nonActiveBe | beName@snapshot}] newBeName
Create a new boot environment named newBeName.
If the -r flag is given, a recursive boot environment will be
made. See Boot Environment Structures for a discussion on
different layouts.
If the -e flag is specified, the new environment will be cloned
from the given nonActiveBe or beName@snapshot. Otherwise, the
new environment will be created from the currently booted
environment.
If bectl is creating from another boot environment, a snapshot of
that boot environment will be created to clone from.
create [-r] beName@snapshot
Create a snapshot of the boot environment named beName.
If the -r flag is given, a recursive snapshot of the boot
environment will be created. A snapshot is created for each
descendant dataset of the boot environment. See Boot Environment
Structures for a discussion on different layouts.
No new boot environment is created with this subcommand.
create -E newBeName
Create a new empty boot environment named newBeName.
destroy [-Fo] beName[@snapshot]
Destroy the given beName boot environment or beName@snapshot
snapshot without confirmation, unlike in beadm(8). Specifying -F
will automatically unmount without confirmation.
By default, bectl will warn that it is not destroying the origin
of beName. The -o flag may be specified to destroy the origin as
well.
export sourceBe
Export sourceBe to stdout(4). stdout(4) must be piped or
redirected to a file.
import targetBe
Import targetBe from stdin(4).
jail [-bU] [{-o key=value | -u key}]... beName [utility [argument ...]]
Create a jail of the given boot environment. Multiple -o and -u
arguments may be specified. -o will set a jail parameter, and -u
will unset a jail parameter.
By default, jails are created in interactive mode and /bin/sh is
executed within the jail. If utility is specified, it will be
executed instead of /bin/sh. The jail will be destroyed and the
boot environment unmounted when the command finishes executing,
unless the -U argument is specified.
The -b argument enables batch mode, thereby disabling interactive
mode. The -U argument will be ignored in batch mode.
The name, host.hostname, and path must be set, the default values
are specified below.
All key=value pairs are interpreted as jail parameters as
described in jail(8). The following default parameters are
provided:
allow.mount true
allow.mount.devfs true
enforce_statfs 1
name set to jail ID
host.hostname bootenv
path set to a path in /tmp generated by libbe(3)
All default parameters may be overwritten.
list [-aDHs] [{-c property | -C property}]
Display all boot environments. The Active field indicates
whether the boot environment is active now (N); active on reboot
(R); is used on next boot once (T); or combination of (NRT).
-a Display all datasets.
-D Display the full space usage for each boot environment,
assuming all other boot environments were destroyed.
-H Used for scripting. Do not print headers and separate
fields by a single tab instead of arbitrary white space.
-s Display all snapshots as well.
-c property
Sort boot environments by the given ZFS dataset property.
The following properties are supported:
name (the default)
creation
origin
used
usedbydataset
usedbyrefreservation
usedbysnapshots
Short forms usedds, usedrefreserv and usedsnap are also
supported.
-C property
Same as the -c option, but displays in descending order.
The -D option is ignored when either the -s or -a option is used.
mount beName [mountpoint]
Mount the given boot environment.
If a nonexistent mountpoint is given: bectl will make the
directory, including intermediate directories as required.
If no mountpoint is given: bectl will make a directory such as
be_mount.c6Sf in /tmp. Randomness in the last four characters of
the directory name will prevent mount point conflicts. Unmount
of an environment, followed by mount of the same environment
without giving a mountpoint, will result in a different randomly-
named mountpoint.
rename origBeName newBeName
Rename the given origBeName to the given newBeName. The boot
environment will not be unmounted for this rename to occur.
ujail {jailId | jailName | beName}
unjail {jailId | jailName | beName}
Destroy the jail created from the given boot environment.
umount [-f] beName
unmount [-f] beName
Unmount the given boot environment, if it is mounted. Specifying
-f will force the unmount if busy.
Unmount will not remove the mount point.
Boot Environment Structures
The traditional FreeBSD boot environment layout, as created by the Auto
ZFS option to bsdinstall(8), is a "shallow" boot environment structure,
where boot environment datasets do not have any directly subordinate
datasets. Instead, they're organized off in zroot/ROOT, and they rely on
datasets elsewhere in the pool having canmount set to off. For instance,
a simplified pool may be laid out as such:
% zfs list -o name,canmount,mountpoint
NAME CANMOUNT MOUNTPOINT
zroot
zroot/ROOT noauto none
zroot/ROOT/default noauto none
zroot/home on /home
zroot/usr off /usr
zroot/usr/src on /usr/src
zroot/var off /var
In that example, zroot/usr has canmount set to off, thus files in /usr
typically fall into the boot environment because this dataset is not
mounted. zroot/usr/src is mounted, thus files in /usr/src are not in the
boot environment.
The other style of boot environments in use, frequently called "deep boot
environments", organizes some or all of the boot environment as
subordinate to the boot environment dataset. For example:
% zfs list -o name,canmount,mountpoint
NAME CANMOUNT MOUNTPOINT
zroot
zroot/ROOT noauto none
zroot/ROOT/default noauto none
zroot/ROOT/default/usr noauto /usr
zroot/ROOT/default/usr/local noauto /usr/local
zroot/var on /var
Note that the subordinate datasets now have canmount set to noauto.
These are more obviously a part of the boot environment, as indicated by
their positioning in the layout. These subordinate datasets will be
mounted by the zfsbe rc(8) script at boot time. In this example, /var is
excluded from the boot environment.
bectl subcommands that have their own -r operate on this second, "deep"
style of boot environment, when the -r flag is set. A future version of
bectl may default to handling both styles and deprecate the various -r
flags.
EXAMPLES
Create a boot environment, named with today's date, containing snapshots
of the root dataset and of all child datasets:
bectl create -r `date +%Y%m%d`
Mount a previous boot environment, yesterdaysbe, to /mnt:
bectl mount yesterdaysbe /mnt
SEE ALSO
libbe(3), zfsprops(7), beinstall.sh(8), jail(8), loader(8), zfs(8),
zpool(8)
HISTORY
bectl and libbe(3) were written by Kyle Kneitinger (kneitinger)
<kyle@kneit.in> as a 2017 Google Summer of Code project, with Allan Jude
(allanjude) <allanjude@freebsd.org> as mentor.
bectl and this manual page were derived from beadm(8).
AUTHORS
Slawomir Wojciech Wojtczak (vermaden) <vermaden@interia.pl> is the
creator and maintainer of beadm(8).
Bryan Drewery (bdrewery) <bryan@shatow.net> contributed child dataset
fixes, and wrote the beadm(8) manual page.
Most later changes to bectl, and to this page, were written by
Kyle Evans (kevans) <kevans@freebsd.org>.
FreeBSD 15.1-STABLE-HBSD February 4, 2026 BECTL(8)