A small note, in addition to article about the root partition on ZFS .
the previous article : Debian, root on ZFS.
It is necessary to copy the images of partitions, for example to a USB flash drive, in case of failure, it was possible to recover to the previous working state:
mount /dev /disk /by-id /usb-Corsair_Flash_Voyager-0: 0-part1 /mnt /usb /
dd if = /dev /disk /by-id /ata-Micron_1100-part2 of = /mnt /usb /micron_boot.img bs = 4M
dd if = /dev /disk /by-id /ata-Samsung_SSD_850_PRO-part2 of = /mnt /usb /samsung_boot.img bs = 4M
umount /mnt /usb