docker_save.sh

#!/bin/bash
# __author__: tuan t. pham <tuan at vt dot edu>

# Description: a glorious shell script to save the typing of
# for i in `docker images | tail -n +2...;do docker save $i | xz ...>;done
# This script will save your docker image(s) to .tar.xz file(s)

# To load the saved image(s):
# $ for i in `ls *.xz`; do
#		xzcat $i | docker load
#	done

OPTS=":l:o:n:c:h"
DEBUG=${DEBUG:=0}
OUTDIR=${OUTDIR:=.}
COMPRESS_LEVEL=6

# Define your own filter command to filter out the output of `docker images`
FILTER=${FILTER:="grep -vi \"^<None>\""}
CPUS=${CPUS:=`grep -c processor /proc/cpuinfo`}
DEF_IMG_CMD="docker images | tail -n +2 | $FILTER | awk '{print \$1\":\"\$2}'"
IMG_CMD=${IMG_CMD:=$DEF_IMG_CMD}

# see https://en.wikipedia.org/wiki/ANSI_escape_code#Colors
# the color code snippet is from https://github.com/docker/docker @ docker/contrib/check-config.sh
declare -A colors=(
	[black]=30
	[red]=31
	[green]=32
	[yellow]=33
	[blue]=34
	[magenta]=35
	[cyan]=36
	[white]=37
)
# Ex:
# color red
# echo something
# color reset
function color()
{
	color=( '1' )
	if [ $# -gt 0 ] && [ "${colors[$1]}" ]; then
		color+=( "${colors[$1]}" )
	else
		color=()
	fi
	# set delimiter
	local IFS=';'
	echo -en '\033['"${color[*]}"m
}

# reverse docker's order
# wrap_color <color> <"text">
function wrap_color()
{
	color "$1"
	shift
	echo -ne "$@"
	color reset
	echo
}

function log()
{
	if [ "$DEBUG" = 1 ]; then
		eval "echo $*"
	fi
}

function dump_vars()
{
	VAR_LIST="OPTS DEBUG OUTDIR COMPRESS_LEVEL FILTER CPUS DEF_IMG_CMD IMG_CMD"
	for e in $VAR_LIST; do
		d="$e"
		d=`eval echo "\\$$d"`
		echo "$e=$d"
	done
}

function help_msg()
{ #onc
	echo "$(wrap_color red "Usage:") $0"
	echo -e "\t$(wrap_color yellow "[--help|-h]:") Help message"
	echo
	echo -e "$(wrap_color yellow "Options:")"
	echo -e "\t-h This help message"
	echo
	echo -e "\t-l <DIR>"
	echo -e "\t\tLoad images from DIR"
	echo -e "\t\tMust specify the directory"
	echo -e "\tOR just run something like this"
	echo -e "\t\tfor i in \`ls *.xz\`; do xzcat \$i | docker load; done"
	echo
	echo -e "\t-o <DIR>"
	echo -e "\t\tOutput directory for saved docker images"
	echo -e "\t\tDEFAULT is the current working directory"
	echo
	echo -e "\t-n <N>"
	echo -e "\t\tNumber of cpu core to be used for compression"
	echo -e "\t\tDEFAULT is the number of available cores, $(grep -c processor /proc/cpuinfo)"
	echo
	echo -e "\t-c <N>"
	echo -e "\t\tCompression level"
	echo -e "\t\tDEFAULT=$COMPRESS_LEVEL; MIN=0, MAX=9"
	echo
	echo -e "$(wrap_color yellow "Environment Variables:")"
	echo -e "\t$(wrap_color red "IMG") List of docker images to be saved"
	echo -e "\t   DEFAULT is the list of images from docker images"
	echo
	echo -e "\t$(wrap_color red "COMPRESSOR") Compressor command line; take STDIN and output to STDOUT"
	echo -e "\t\tDEFAULT COMPRESSOR=\"pxz -T$CPUS -c$COMPRESS_LEVEL - \""
	echo
	echo -e "\t$(wrap_color red "COMP_EXT") The file extension if the above variable is set"
	echo -e "\t\tDEFAULT COMP_EXT=xz"
	echo
	echo -e "\t$(wrap_color red "FILTER") The command to filter the output of \`docker images\`"
	echo -e "\t\tDefault FILTER=\"grep -vi \"^<None>\""
	echo
	echo -e "$(wrap_color yellow Examples:)"
	echo -e "\t1) Save all current docker images except the <None> ones to current working directory"
	echo -e "\t\t\$ $0"
	echo
	echo -e "\t2) Save one container"
	echo -e "\t\t\$ IMG=debian:jessie $0"
	echo
	echo -e "\t3) Use 4 cpu cores for pxz (default), output to 'images' directory, maximum compression level"
	echo -e "\t\t\$ $0 -n 4 -o docker_images -c 9"
	echo
	echo -e "\t4) Load docker images from a directory"
	echo -e "\t\t\$ $0 -l docker_images"
	echo
	echo -e "__author__: tuan t. pham <tuan at vt dot edu>"
}

function set_compressor()
{
	if [ "$COMPRESSOR" ]; then
		echo "Using user compressor command '$COMPRESSOR'"
		echo "Filename extension = .$COMP_EXT"
		return
	fi

	which pxz >/dev/null
	if [ $? = 0 ]; then
		COMPRESSOR="pxz -T$CPUS -c$COMPRESS_LEVEL - "
	else
		which xz >/dev/null
		if [ $? = 0 ]; then
			COMPRESSOR="xz -z -c$COMPRESS_LEVEL "
		fi
	fi

	if [ ! "$COMPRESSOR" ]; then
		echo "Use the default compressor gz"
		COMPRESSOR="gz -c$COMPRESS_LEVEL"
		COMP_EXT="gz"
	else
		COMP_EXT="xz"
	fi
}

function get_img()
{
	if [ ! "$IMG" ]; then
		IMG=$(eval "$IMG_CMD")
	fi
}

# load_images DIR
function load_images()
{
	if [ -d "$1" ]; then
		for d in $(ls "$1"/*.tar.xz); do
			xzcat $d | docker load
		done
	else
		echo "Directory $1 does not exist"
	fi
}

function docker_save()
{
	set_compressor
	echo "Compressor Command = '$COMPRESSOR'"
	get_img
	echo -e "Saving $(echo "$IMG" | sed -s "s/ /\n/g" | wc -l) image(s):\n$IMG"

	for i in $IMG
	do
		echo -e "\nSaving docker image '$i'"
		OUTFILE=$(echo $i | tr '\:' '_')
		CMD="docker save \$i | \$COMPRESSOR > \$OUTDIR/\$OUTFILE.tar.$COMP_EXT"
		echo "Output file = '$OUTDIR/$OUTFILE.tar.$COMP_EXT'"
		# echo $CMD
		eval "$CMD"
	done
}

function parse_opts()
{
	while getopts $OPTS opt; do
		case $opt in
			l)
				log "Setting loading files from directory $OPTARG"
				LOAD_DIR=$OPTARG
				;;
			o)
				log "Setting the OUTDIR to \'$OPTARG\'"
				OUTDIR=$OPTARG
				[ -d "$OUTDIR" ] || mkdir -p $OUTDIR
				;;
			n)
				log "Setting the number of cpus to $OPTARG"
				CPUS=$OPTARG
				;;
			c)
				log "Setting compression level $OPTARG"
				COMPRESS_LEVEL=$OPTARG
				;;
			h)
				log "Setting -h option"
				help_msg
				exit 0
				;;
			\?)
				echo "Invalid option(s)"
				help_msg
				exit 1
				;;
		esac
	done
}

function main()
{
	if [ "$1" = "--help" ]; then
		help_msg
		exit 0
	fi

	parse_opts "$@"

	[ "$LOAD_DIR" ] && load_images $LOAD_DIR && exit 0
	[ "$DEBUG" = 1 ] && dump_vars
	docker_save
}

main "$@"