man apt-clone
APT-CLONE(8) APT-CLONE(8) NAME apt-clone - ZFS integrated APT package handling utility -- command- line interface SYNOPSIS apt-clone [-hltsyv] [-a=clone-name] [-r=clone-name] [-b=bootmenu-count] [-k=clone-count] [-x=http-proxy] apt-cmd pkg1 pkg2... DESCRIPTION apt-clone is the command-line tool for handling packages, and may be considered the user's "front-end" to the apt-get(8). It manages GRUB menu and ZFS 'syspool' filesystems. Two upgrade methods supported: 1) safe upgrades via cloning a currently active filesystem and later ch- rooting into it to perform actual upgrade operation; 2) in-place (live) upgrades by checkpointing a currently active filesystem prior to any upgrade modifications done by apt-get utility. The live upgrad- ing, as the name implies, happens in-place on the running system, and without reboot. Unless the safe -s option is explicitly specified, the system will automatically detect whether the upgrade will require re- boot, and if so, it will clone the active filesystem and safely per- form the software upgrade within this ZFS clone. A user then has two options: reboot into the new (upgraded) system folder or continue working (and possibly activate the upgrade and reboot into it later)...
Full man page at http://www.nexenta.org/os/AptCloneMan