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Manual Pages  — BECTL


bectl – Utility to manage boot environments on ZFS



bectl activate [-t] beName
bectl check
bectl create [-r] [-e {nonActiveBe | beName @snapshot}] newBeName
bectl create [-r] beName@snapshot
bectl destroy [-amp;Fo] beName[ @snapshot]
bectl export sourceBe
bectl import targetBe
bectl jail [-bU] [{-o key =value | -u key }]... beName [utility [argument ...]]
bectl list [-aDHs] [-c property] [-C property] [{-c property | -C property }]
bectl mount beName [mountpoint]
bectl rename origBeName newBeName
bectl { ujail | unjail} {jailId | jailName | beName}
bectl { umount | unmount} [-f] beName

bectl [-hamp;?]


The bectl command is used to setup and interact with ZFS boot environments, which are bootable clones of datasets.

Boot environments allow the system to be upgraded, while preserving the old system environment in a separate ZFS dataset.

The following commands are supported by bectl:
activate [-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.
check Performs a silent sanity check on the current system. 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 command.

destroy [-amp;Fo] beName[ @snapshot] Destroy the given beName boot environment or beName @snapshot snapshot without confirmation, unlike in beadm(1). 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 /tmpgenerated 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 ( amp;N); active on reboot ( amp;R); or both ( amp;NR).

  Display all datasets.
  Display the full space usage for each boot environment, assuming all other boot environments were destroyed.
  Used for scripting. Do not print headers and separate fields by a single tab instead of arbitrary white space.
  Display all snapshots as well.
-c property
  Sort boot environments by given property name. The following properties are supported:

name (default output)
-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]
  Temporarily mount the boot environment. Mount at the specified mountpoint if provided.
rename origBeName newBeName
  Rename the given origBeName to the given newBeName. The boot environment will not be unmounted in order 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.

bectl prints usage information if -h or -amp;? is specified.

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/ROOT              noauto          none
zroot/ROOT/default      noauto          none
zroot/usr               off             /usr
zroot/usr/home          on              /usr/home
zroot/var               on              /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/home is mounted, thus files in /usr/home 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/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 commands 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.


libbe(3), beinstall.sh(8), jail(8), zfs(8), zpool(8)


bectl is based on beadm(1) and was implemented as a project for the 2017 Summer of Code, along with libbe(3).


bectl was written by Kyle Kneitinger (kneitinger) <Mt kyle@kneit.in>.

beadm(1) was written and is maintained by Slawomir Wojciech Wojtczak (vermaden) <Mt vermaden@interia.pl>.

Bryan Drewery (bdrewery) <Mt bryan@shatow.net> wrote the original beadm(1) manual page that this one is derived from.

BECTL (8) March 31, 2022

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