BTRFS Snapshot

btrfs-snapshot

#!/bin/bash

# Parse arguments:
SOURCE=$1
TARGET=$2
SNAP=$3
COUNT=$4
QUIET=$5

# Function to display usage:
usage() {
    scriptname=`/usr/bin/basename $0`
cat <<EOF
$scriptname: Take and rotate snapshots on a btrfs file system

  Usage:
  $scriptname source target snap_name count [-q]

  source:    path to make snaphost of
  target:    snapshot directory
  snap_name: Base name for snapshots, to be appended to
             date "+%F_%H-%M-%S_%Z"
  count:     Number of snapshots in the timestamp-@snap_name format to
             keep at one time for a given snap_name.
  [-q]:      Be quiet.

Example for crontab:
15,30,45  * * * *   root    /usr/local/bin/btrfs-snapshot / /.btrfs quarterly 4 -q
0         * * * *   root    /usr/local/bin/btrfs-snapshot / /.btrfs hourly 8 -q

Example for anacrontab:
1             10      daily_snap      /usr/local/bin/btrfs-snapshot / /.btrfs daily 8
7             30      weekly_snap     /usr/local/bin/btrfs-snapshot / /.btrfs weekly 5
@monthly      90      monthly_snap    /usr/local/bin/btrfs-snapshot / /.btrfs monthly 3


EOF
    exit
}

# Basic argument checks:
if [ -z $COUNT ] ; then
    echo "COUNT is not provided."
    usage
fi

if [ ! -z $6 ] ; then
    echo "Too many options."
    usage
fi

if [ -n "$QUIET" ] && [ "x$QUIET" != "x-q"  ] ; then
    echo "Option 4 is either -q or empty. Given: \"$QUIET\""
    usage
fi

# check that source exists
if [ ! -d "$SOURCE" ]; then
  if [ -z $QUIET ]; then
      echo "$SOURCE does not exist or is not mounted"
  fi
  exit 1
fi

# $max_snap is the highest number of snapshots that will be kept for $SNAP.
max_snap=$(($COUNT -1))

# Clean up older snapshots:
for i in `ls $TARGET|sort |grep @${SNAP}|head -n -${max_snap}`; do
    cmd="/sbin/btrfs subvolume delete $TARGET/$i"
    if [ -z $QUIET ]; then
        echo $cmd
    fi
    $cmd >/dev/null
done

# Create new snapshot:
cmd="/sbin/btrfs subvolume snapshot $SOURCE $TARGET/`date "+%F_%H-%M-%S_%Z-@${SNAP}"`"
if [ -z $QUIET ]; then
    echo $cmd
fi
$cmd >/dev/null