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BECTL(8) 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] 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 envionments allow system changes to be tested safely, as they are se- lectable 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 lay- outs. 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 environ- ments. If boot environments are supported and used, bectl will exit with a status code of 0. Any other status code is not cur- rently 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 environ- ment 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. destroy [-Fo] beName[@snapshot] Destroy the given beName boot environment or beName@snapshot snap- shot 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 redi- rected 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 exe- cuted 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, as- suming 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 direc- tory, 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 envi- ronment 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 simpli- fied 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 typ- ically 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 envi- ronment. 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 15.0 June 13, 2025 BECTL(8)
NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | HISTORY | AUTHORS
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