zfs: perform a recursive roll-back

zfs_recursive_rollback

#!/bin/sh
# zfs_recursive_rollback
#
# ©2021 Boruch Baum <boruch_baum@gmx.com>
# License: GPL3+
#
# usage: zfs_recursive_rollback dataset@snapshot
#
#                               dataset @snapshot
#
#                               dataset snapshot

CMD="zfs rollback -r -R -f "
CMD_OPTS="
  -r : also destroy newer snapshots and bookmarks
  -f : forcibly unmount their clones
  -R : also destroy those clones"

rollback_recursively() {
  # The zfs spec forbids spaces, etc. in dataset and snapshot names
  for EACHSNAP in $(zfs list -H -t snapshot -r ${DATASET} | grep ${SNAP} | cut -f 1); do
    if [ $# -ne 0 ] ; then
      # Dry-run: Don't actually do anything
      printf "roll back to ${EACHSNAP}\n"
    else
      # The real operation
      printf "rolling back to ${EACHSNAP} : "
      eval ${CMD} ${EACHSNAP}
      printf "  done.\n"
    fi
  done
}

exit_unless_confirms_with_yes() {
  read -p "enter 'yes' to continue: " REPLY
  if [ "${REPLY}" != "yes" ] ; then
    printf "aborting..\n"
    exit
  fi
}

# main() BEGIN

# main() validate input
if [ $# -eq 2 ]; then
  DATASET="$1"
  SNAP="$2"
  [ -z "${SNAP%%@*}" ] || SNAP="@${SNAP}"
elif [ $# -eq 1 ]; then
  DATASET="${1%%@*}"
  SNAP="${1##*@}"
  if [ "$1" = "${DATASET}" -o "$1" = "${SNAP}" ] ; then
    printf "could not parse pool@snapshot: $1\n"
    exit
  SNAP="@${SNAP}"
  fi
else
  printf "usage: $0 dataset@snapshot\nexample: $0 rpool/ROOT/usr@2022-01-01_001\n"
  exit
fi
COUNT=$(zfs list -H -t snapshot -r "${DATASET}" | grep -c "${SNAP}")
if [ ${COUNT} -eq 0 ] ; then
  printf "snapshot not found for dataset.\nsnapshot: ${SNAP}\ndataset:  ${DATASET}\n"
  exit
fi

# main() verify operation
clear
printf "zfs_recursive_rollback\n
WARNING: This should be thought of as an *extreme* action,
         a catastrophic last resort!\n
ADVICE: Most user cases can be resolved by temporarily
        mounting snapshot(s) and restoring specific data.\n
Continuing will catastrophically perform a recursive zfs rollback,
destroying snapshots, bookmarks, and clones!\n
Are you certain that you really want to rollback ALL datasets
under        $DATASET
to snapshot: $SNAP ?\n
Doing this will perform: ${CMD_OPTS}\n\n"
exit_unless_confirms_with_yes
clear
printf "\nOK. Here's what's about to happen:\n"
rollback_recursively "dry-run"
printf "Are you certain that you're OK with all of that?\n\n"
exit_unless_confirms_with_yes

# main() perform operation
rollback_recursively