make-snapshot

#!/bin/bash

############################################################
##################### CONSTANTS ############################
############################################################

Timefile=".snapshot-timestamp"

indent() { sed 's/^/   /'; }
die()    { echo "Error: $1 (code=$2)" >&2 ; exit $2; }
warn()   { echo "Warning: $1" >&2 ; }

############################################################

set -o pipefail -o nounset

Self=$(basename $0)

OPTIONS=ivn
LONGOPTS=initial,verbose,dry-run
# long options to short ones
for arg in "$@"
do
    shift
    case "$arg" in
        "--initial")    set -- "$@" "-i" ;;
        "--dry-run")    set -- "$@" "-n" ;;
        "--verbose")    set -- "$@" "-v" ;;
        *)              set -- "$@" "$arg"
  esac
done

# defaults
Initial=n
Verbose=n
DryRun=n
# parse options
OPTIND=1
while getopts "inv" opt
do
    case "$opt" in
	"i") Initial=y ;;
        "n") DryRun=y ;;
        "v") Verbose=y ;;
        "?") die "unknown option" 10 ;;
    esac
done
shift $(expr $OPTIND - 1) # remove options from positional parameters

# handle non-option arguments
[[ $# -gt 1 ]] && die "$Self: only one single configuration file can be provided." 12

############################################################

if [ $# -eq 1 ]
then
	[ -f "$1" -a -r "$1" ] || die "$Self: configuration file $1 not found or not readable." 20
	# source the job config
	source "$1"
	if [ -z ${Job+x} ]; then
		Job=$(basename -s .conf $1)
	fi
	Self="${Self}@${Job}"
fi

# check whether all mandatory variables were set in config file or environment

[ -z ${LIB_DIR+x} ]		&& die "State directory (LIB_DIR) is required." 21
[ -z ${LOG_DIR+x} ]		&& die "Log directory (LOG_DIR) is required." 21
[ -z ${TAG+x} ]			&& die "Snapshot tag format (TAG) is required." 21
[ -z ${BACKUP_TREE+x} ]		&& die "Tree to be snapshotted (BACKUP_TREE) is required." 21
[ -z ${BACKUP_FILTER+x} ]	&& die "Filter filename (BACKUP_FILTER) is required." 21
[ -z ${REMOTE_BASE+x} ]		&& die "Destination (REMOTE_BASE) is required." 21
[ -z ${Job+x} ]			&& die "Job name (Job) is required." 21

############################################################
############################################################
############################################################

if [ -e "${LIB_DIR}/${Job}.last" ]
then	
	# if we have a last snapshot tag, we shouldn't be on an initial run
	[ "$Initial"  = "y" ] && die "Error: initial run chosen, but prior snapshot exists. Remove ${LIB_DIR}/${Job}.last to recreate initial snapshot." 30
	[ -r "${LIB_DIR}/${Job}.last" ] || die "${LIB_DIR}/${Job}.last is not readable." 31
	Oldstamp="$(cat "${LIB_DIR}/${Job}.last")"
else	
	# if we have no last snapshot tag saved, we should have been called as initial run
	[ "$Initial" != "y" ] && die "Error: cannot read tag of last snapshot from ${LIB_DIR}/${Job}.last, and --initial was not passed." 32
fi

############################################################

touch "${BACKUP_TREE}/${Timefile}" || die "Cannot touch(1) timestamp file '${BACKUP_TREE}/${Timefile}'" 33

chmod 0444 "${BACKUP_TREE}/${Timefile}" || warn "Could not make timestamp file '${BACKUP_TREE}/${Timefile}' read-only."

Timestamp="$(date ${TAG_OPTIONS:-} -r "${BACKUP_TREE}/${Timefile}" +"${TAG}")"
[ -z ${Timestamp+x} ] && die "Problem generating new snapshot tag." 34

echo "Creating new snapshot of ${BACKUP_TREE}:"
echo " new tag:  $Timestamp" 
echo " last tag: ${Oldstamp:-INITIAL RUN}"
echo " target:   $REMOTE_BASE"
echo

[ -n "${LOCK_DIR:+x}" ] && [ -e "${LOCK_DIR}/${Job}" ] && die "Snapshot already in progress, exiting." 40

echo -n "1. Placing lock file: "

if [ -n "${LOCK_DIR:+x}" ]	# lock dir is optional
then
	if [ ! -d "${LOCK_DIR}" ]	# it might rest on a temporary filesystem
	then
		mkdir -p ${LOCK_DIR} || die "Failed, could not create directory ${LOCK_DIR}." 50
	fi
	touch "${LOCK_DIR}/${Job}" && echo "OK." || die "Failed." 55
else
	echo "[ skipped - LOCK_DIR not set]"
fi

############################################################

if [ -z ${Oldstamp+x} ]
then
	
	echo "2. Initial run, skipping check of previous snapshot."

else

	echo -n "2. Checking if last tag exists: "

	rsync "${REMOTE_AUTH[@]}" "${REMOTE_BASE}$Oldstamp/" > /dev/null
	RsyncExit=$?

	if [ $RsyncExit -eq 0 ]
	then
		echo "OK."
	else
		die "Failed: rsync returned $RsyncExit." 60
	fi

fi

############################################################

if [ ! -d ${LOG_DIR}/${Job} ]
then
	mkdir -p ${LOG_DIR}/${Job} || die "Error: could not create log directory ${LOG_DIR}/${Job}." 70
fi

Logfile="${LOG_DIR}/${Job}/${Timestamp:-$(date +%Y-%m-%d_%H:%M%z)}"

############################################################
### real work starts here ##################################
############################################################

echo -n "3. Creating snapshot: "

if [ -z ${Oldstamp+x} ] || [ "${Oldstamp}" = "${Timestamp}" ]
then
	[ -z ${Oldstamp+x} ] && echo -n "(initial) " || echo -n "(static) "
	#
	# initial snapshot or static tag - rsync in default mode
	#
	if [ "$DryRun"  = "n" ]
	then
		rsync -ai --filter="dir-merge ${BACKUP_FILTER}" "${REMOTE_AUTH[@]:---}" "${BACKUP_TREE}/" "${REMOTE_BASE}$Timestamp/" > ${Logfile}
		RsyncExit=$?
	else
		echo
		rsync -avn --filter="dir-merge ${BACKUP_FILTER}" "${REMOTE_AUTH[@]:---}" "${BACKUP_TREE}/" "${REMOTE_BASE}$Timestamp/"
		RsyncExit=$?
	fi
else
	echo -n "(timestamped) "
	#
	# changing tag: snapshot-style, rsync with --link-dest
	#
	if [ "$DryRun"  = "n" ]
	then
		rsync -ai --filter="dir-merge ${BACKUP_FILTER}" --link-dest="../$Oldstamp" "${REMOTE_AUTH[@]:---}" "${BACKUP_TREE}/" "${REMOTE_BASE}$Timestamp/" > ${Logfile}
		RsyncExit=$?
	else
		echo
		rsync -avn --filter="dir-merge ${BACKUP_FILTER}" --link-dest="../$Oldstamp" "${REMOTE_AUTH[@]:---}" "${BACKUP_TREE}/" "${REMOTE_BASE}$Timestamp/"
		RsyncExit=$?
	fi
fi

if [ $RsyncExit -eq 0 -o $RsyncExit -eq 24 ] # code 24: source file vanished during transfer, that can happen
then
	echo "OK."
else
	die "Failed: rsync returned $RsyncExit." 71
fi

############################################################

echo -n "4. Saving current tag to ${LIB_DIR}/${Job}.last: "

if [ ! -d ${LIB_DIR} ]
then
	mkdir -p ${LIB_DIR}
	if [ $? -ne 0 ]
	then
		die "Error: could not create state directory ${LIB_DIR}." 80
	fi
fi

if [ "$DryRun"  = "n" ]
then
	echo $Timestamp > ${LIB_DIR}/${Job}.last
	if [ $? -eq 0 ]
	then
		echo "OK."
	else
		die "Failed." 81
	fi
else
	echo "[skipped - dry run]"
fi

echo -n "5. Removing lock file: "

if [ -n "${LOCK_DIR:+x}" ]	# lock dir is optional
then
	rm -f "${LOCK_DIR}/${Job}" && echo "Done." || echo "Failed."
else
	echo "[ skipped - LOCK_DIR not set]"
fi