backup.sh

#!/bin/bash
#------------------------------------------------------------------------------------
#Generic file backup test using rsync
#Usage: ./filename [--run]
#
# Options
# --run: run the backup, script performs simulation run by default if not specified
#------------------------------------------------------------------------------------
#User input
#--------------------------------------------------------------------
SOURCE="/mnt/Toshiba_3TB/"
SNAPSHOT_LIMIT=2 #number of snapshots to preserve (0=infinite)
#--------------------------------------------------------------------

echo
echo
echo
ARG1=$1
TARGET="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
EXCLUDE_FILE="${TARGET}/exclude"

#Create Trash folder if it does not exist
TRASH_FOLDER_NAME=".trash"
TRASH_DIR="${TARGET}/${TRASH_FOLDER_NAME}/"
if [ ! -d "${TRASH_DIR}" ]; then
    mkdir "${TRASH_DIR}"
fi

#Create snapshot folder if it does not exist
SNAPSHOT_FOLDER_NAME="snapshots"
SNAPSHOT_DIR="${TARGET}/${SNAPSHOT_FOLDER_NAME}/"
if [ ! -d "${SNAPSHOT_DIR}" ]; then
    mkdir "${SNAPSHOT_DIR}"
fi

#Create logs folder
LOG_DIR="${TARGET}/logs/"
if [ ! -d "${LOG_DIR}" ]; then
    mkdir "$LOG_DIR"
fi
LOG_DIR_DRY_RUN="${LOG_DIR}dry_run/"
if [ ! -d "$LOG_DIR_DRY_RUN" ]; then
    mkdir "$LOG_DIR_DRY_RUN"
fi
LOG_DIR_SNAPSHOTS="${LOG_DIR}snapshots/"
if [ ! -d "$LOG_DIR_SNAPSHOTS" ]; then
    mkdir "$LOG_DIR_SNAPSHOTS"
fi

#fetch number of snapshot folders present
SNAPSHOT_COUNT=`ls -l "$SNAPSHOT_DIR" | grep ^d | wc -l`

SNAPSHOT_HANDLE="Snapshot_"
TIMESTAMP=`date +%Y%m%d%H%M%S`
SNAPSHOT_DIR_NAME="${SNAPSHOT_HANDLE}${TIMESTAMP}"
LATEST_SNAPSHOT_NAME=

#Create log file for current session
LOG_HANDLE="log_"
LOGFILE_PATH=
if [ "$ARG1" == "--run" ]; then
    LOGFILE_PATH="${LOG_DIR_SNAPSHOTS}${LOG_HANDLE}${TIMESTAMP}"
    touch "$LOGFILE_PATH"
else
    LOG_HANDLE="log_dryrun"
    LOGFILE_PATH="${LOG_DIR_DRY_RUN}${LOG_HANDLE}"
    if [ -f "$LOGFILE_PATH" ]; then
        mv --backup=t "$LOGFILE_PATH" "$TRASH_DIR"
    fi
    touch "$LOGFILE_PATH"
fi

#options (WARNING: DO NOT specify any dry run tags such as "-n" here)
OPTIONS=(\
-aAXSv \
--delete \
--one-file-system\
)

if [ "$ARG1" != "--run" ]; then
    OPTIONS+=(-n)
    OPTIONS+=(--log-file=$LOGFILE_PATH)
elif [ "$ARG1" == "--run" ]; then
    OPTIONS+=(--log-file=$LOGFILE_PATH)
fi

#fetch most recent snapshot (assumed last folder in snapshot directory)
if [ $SNAPSHOT_COUNT -ne 0 ]; then
    temp=(`ls -l ${SNAPSHOT_DIR} | grep ^d | tail -1`)
    LATEST_SNAPSHOT_NAME=${temp[-1]}
    LATEST_SNAPSHOT_DIR=${SNAPSHOT_DIR}${LATEST_SNAPSHOT_NAME}
fi

EXCLUDE="--exclude-from=$EXCLUDE_FILE"
RSYNC_COMMAND="${OPTIONS[@]} ${EXCLUDE} ${SOURCE} ${SNAPSHOT_DIR}"

#perform a dry run
if [ "$ARG1" != "--run" ]; then
    if [ $SNAPSHOT_COUNT -ne 0 ]; then
        cp -al "$LATEST_SNAPSHOT_DIR" "${SNAPSHOT_DIR}dummy"
    else
        mkdir "${SNAPSHOT_DIR}dummy"
    fi
    rsync ${RSYNC_COMMAND}"dummy"
    rm -rf ${SNAPSHOT_DIR}"dummy"
else
    if [ $SNAPSHOT_COUNT -eq 0 ]; then
        rsync ${RSYNC_COMMAND}"${SNAPSHOT_DIR_NAME}"

    elif [ $SNAPSHOT_LIMIT -eq 0 ] || [ $SNAPSHOT_COUNT -lt $SNAPSHOT_LIMIT ]; then
        #run backup with hardlinks to latest snapshot
        cp -al "$LATEST_SNAPSHOT_DIR" "${SNAPSHOT_DIR}${SNAPSHOT_DIR_NAME}";
        rsync ${RSYNC_COMMAND}"${SNAPSHOT_DIR_NAME}"

    elif [ $SNAPSHOT_LIMIT -ne 0 ] && [ $SNAPSHOT_COUNT -ge $SNAPSHOT_LIMIT ]; then
        while [ $SNAPSHOT_COUNT -ge $SNAPSHOT_LIMIT ]; do
            #fetch oldest snapshot (assumed first folder in snapshot directory)
            temp=(`ls -l ${SNAPSHOT_DIR} | grep ^d | head -1`)
            OLDEST_SNAPSHOT_NAME=${temp[-1]}
            OLDEST_SNAPSHOT_DIR=${SNAPSHOT_DIR}${OLDEST_SNAPSHOT_NAME}

            #delete oldest snapshot
            mv --backup=t ${OLDEST_SNAPSHOT_DIR} ${TRASH_DIR}
            SNAPSHOT_COUNT=`ls -l "$SNAPSHOT_DIR" | grep ^d | wc -l`

            #fetch oldest associated snapshot logfile
            temp=(`ls -l ${LOG_DIR_SNAPSHOTS} | grep ^- | head -1`)
            OLDEST_SNAPSHOT_LOG_NAME=${temp[-1]}
            OLDEST_SNAPSHOT_LOG_DIR=${LOG_DIR_SNAPSHOTS}${OLDEST_SNAPSHOT_LOG_NAME}

            #delete oldest associated snapshot logfile
            mv --backup=t ${OLDEST_SNAPSHOT_LOG_DIR} ${TRASH_DIR}
        done

        #run backup with hardlinks to latest snapshot
        cp -al "$LATEST_SNAPSHOT_DIR" "${SNAPSHOT_DIR}${SNAPSHOT_DIR_NAME}";
        rsync ${RSYNC_COMMAND}"${SNAPSHOT_DIR_NAME}"
    fi
fi
echo