As long as sysadmins need to maintain, change and update operating systems there is always need to protect against problems that may occur during these operations. Various solutions were used starting from simple backup/restore procedures or copying the contents of system filesystems into spare disks to snapshots and clones recently. None of these solutions were transparent enough or bulletproof enough to provide complete and consistent protection again failures in the change or update process. One of such holy grails is ZFS Boot Environments solution. It protects entire system (and even additional data when needed) against almost any change or update process. As ZFS Boot Environments matured in Solaris/Illumos systems and then on FreeBSD UNIX other systems started to copy its principles to provide similar solutions such as snapper with BTRFS in SUSE or Boot Environment Manager for DragonFly BSD with their HAMMER filesystem. The presentation aims to walk through the history of these solutions with the focus on practical ZFS Boot Environments solutions and examples.