diff --git a/compile.sh b/compile.sh
index dac713a33..5a05aaf92 100755
--- a/compile.sh
+++ b/compile.sh
@@ -15,7 +15,7 @@
 
 SRC="$(dirname "$(realpath "${BASH_SOURCE[0]}")")"
 
-# check for whitespace in $SRC and exit for safety reasons
+# check for whitespace in ${SRC} and exit for safety reasons
 grep -q "[[:space:]]" <<<"${SRC}" && { echo "\"${SRC}\" contains whitespace. Not supported. Aborting." >&2 ; exit 1 ; }
 
 cd "${SRC}" || exit
@@ -29,32 +29,32 @@ else
 	exit 255
 fi
 
-if [[ $EUID == 0 ]] || [[ "$1" == vagrant ]]; then
+if [[ "${EUID}" == "0" ]] || [[ "${1}" == "vagrant" ]]; then
 	:
-elif [[ "$1" == docker || "$1" == dockerpurge || "$1" == docker-shell ]] && grep -q `whoami` <(getent group docker); then
+elif [[ "${1}" == docker || "${1}" == dockerpurge || "${1}" == docker-shell ]] && grep -q "$(whoami)" <(getent group docker); then
 	:
 else
 	display_alert "This script requires root privileges, trying to use sudo" "" "wrn"
-	sudo "$SRC/compile.sh" "$@"
+	sudo "${SRC}/compile.sh" "$@"
 	exit $?
 fi
 
 update_src() {
 	cd "${SRC}" || exit
-	if [[ ! -f $SRC/.ignore_changes ]]; then
+	if [[ ! -f "${SRC}"/.ignore_changes ]]; then
 		echo -e "[\e[0;32m o.k. \x1B[0m] This script will try to update"
 		git pull
 		CHANGED_FILES=$(git diff --name-only)
-		if [[ -n $CHANGED_FILES ]]; then
+		if [[ -n "${CHANGED_FILES}" ]]; then
 			echo -e "[\e[0;35m warn \x1B[0m] Can't update since you made changes to: \e[0;32m\n${CHANGED_FILES}\x1B[0m"
 			while true; do
 				echo -e "Press \e[0;33m<Ctrl-C>\x1B[0m or \e[0;33mexit\x1B[0m to abort compilation, \e[0;33m<Enter>\x1B[0m to ignore and continue, \e[0;33mdiff\x1B[0m to display changes"
 				read -r
-				if [[ "$REPLY" == "diff" ]]; then
+				if [[ "${REPLY}" == "diff" ]]; then
 					git diff
-				elif [[ "$REPLY" == "exit" ]]; then
+				elif [[ "${REPLY}" == "exit" ]]; then
 					exit 1
-				elif [[ "$REPLY" == "" ]]; then
+				elif [[ "${REPLY}" == "" ]]; then
 					break
 				else
 					echo "Unknown command!"
@@ -66,42 +66,45 @@ update_src() {
 	fi
 }
 
-TMPFILE=`mktemp` && chmod 644 $TMPFILE
-echo SRC=$SRC > $TMPFILE
-echo LIB_TAG=$LIB_TAG >> $TMPFILE
-declare -f update_src >> $TMPFILE
-echo update_src >> $TMPFILE
+TMPFILE=$(mktemp)
+chmod 644 "${TMPFILE}"
+cat <<EOF >> "${TMPFILE}"
+SRC="${SRC}"
+LIB_TAG="${LIB_TAG}"
+declare -f update_src
+update_src
+EOF
 
 #do not update/checkout git with root privileges to messup files onwership.
 #due to in docker/VM, we can't su to a normal user, so do not update/checkout git.
-if [[ `systemd-detect-virt` == 'none' ]]; then
-	if [[ $EUID == 0 ]]; then
-		su `stat --format=%U $SRC/.git` -c "bash $TMPFILE"
+if [[ $(systemd-detect-virt) == 'none' ]]; then
+	if [[ "${EUID}" == "0" ]]; then
+		su "$(stat --format=%U "${SRC}"/.git)" -c "bash ${TMPFILE}"
 	else
-		bash $TMPFILE
+		bash "${TMPFILE}"
 	fi
 fi
 
-rm $TMPFILE
+rm "${TMPFILE}"
 
 # Check for required packages for compiling
-if [[ -z "$(which dialog)" ]]; then
+if [[ -z "$(command -v dialog)" ]]; then
 	sudo apt-get update
 	sudo apt-get install -y dialog
 fi
-if [[ -z "$(which getfacl)" ]]; then
+if [[ -z "$(command -v getfacl)" ]]; then
 	sudo apt-get update
 	sudo apt-get install -y acl
 fi
 
 # Check for Vagrant
-if [[ "$1" == vagrant && -z "$(which vagrant)" ]]; then
+if [[ "${1}" == vagrant && -z "$(command -v vagrant)" ]]; then
 	display_alert "Vagrant not installed." "Installing"
 	sudo apt-get update
 	sudo apt-get install -y vagrant virtualbox
 fi
 
-if [[ "$1" == dockerpurge && -f /etc/debian_version ]]; then
+if [[ "${1}" == dockerpurge && -f /etc/debian_version ]]; then
 	display_alert "Purging Armbian Docker containers" "" "wrn"
 	docker container ls -a | grep armbian | awk '{print $1}' | xargs docker container rm &> /dev/null
 	docker image ls | grep armbian | awk '{print $3}' | xargs docker image rm &> /dev/null
@@ -109,20 +112,21 @@ if [[ "$1" == dockerpurge && -f /etc/debian_version ]]; then
 	set -- "docker" "$@"
 fi
 
-if [[ "$1" == docker-shell ]]; then
+if [[ "${1}" == docker-shell ]]; then
 	shift
+	#shellcheck disable=SC2034
 	SHELL_ONLY=yes
 	set -- "docker" "$@"
 fi
 
 # Install Docker if not there but wanted. We cover only Debian based distro install. Else, manual Docker install is needed
-if [[ "$1" == docker && -f /etc/debian_version && -z "$(which docker)" ]]; then
+if [[ "${1}" == docker && -f /etc/debian_version && -z "$(command -v docker)" ]]; then
 
 	# add exception for Ubuntu Focal until Docker provides dedicated binary
 	codename=$(lsb_release -sc)
 	codeid=$(lsb_release -is | awk '{print tolower($0)}')
-	[[ $codeid == linuxmint && $codename == debbie ]] && codename="buster" && codeid="debian"
-	[[ $codename == focal ]] && codename="bionic"
+	[[ "${codeid}" == "linuxmint" && "${codename}" == "debbie" ]] && codename="buster" && codeid="debian"
+	[[ "${codename}" == "focal" ]] && codename="bionic"
 
 	display_alert "Docker not installed." "Installing" "Info"
 	echo "deb [arch=amd64] https://download.docker.com/linux/${codeid} ${codename} edge" > /etc/apt/sources.list.d/docker.list
@@ -131,27 +135,27 @@ if [[ "$1" == docker && -f /etc/debian_version && -z "$(which docker)" ]]; then
 	packages=("curl" "gnupg" "apt-transport-https")
 	for i in "${packages[@]}"
 	do
-	[[ ! $(which $i) ]] && install_packages+=$i" "
+	[[ ! $(command -v "${i}") ]] && install_packages+=${i}" "
 	done
-	[[ -z $install_packages ]] && apt-get update;apt-get install -y -qq --no-install-recommends $install_packages
+	[[ -z "${install_packages}" ]] && apt-get update;apt-get install -y -qq --no-install-recommends "${install_packages}"
 
 	curl -fsSL "https://download.docker.com/linux/${codeid}/gpg" | apt-key add -qq - > /dev/null 2>&1
 	export DEBIAN_FRONTEND=noninteractive
 	apt-get update
 	apt-get install -y -qq --no-install-recommends docker-ce
 	display_alert "Add yourself to docker group to avoid root privileges" "" "wrn"
-	"$SRC/compile.sh" "$@"
+	"${SRC}/compile.sh" "$@"
 	exit $?
 fi
 
 # Create userpatches directory if not exists
-mkdir -p $SRC/userpatches
+mkdir -p "${SRC}"/userpatches
 
 # Create example configs if none found in userpatches
-if ! ls ${SRC}/userpatches/{config-example.conf,config-docker.conf,config-vagrant.conf} 1> /dev/null 2>&1; then
+if ! ls "${SRC}"/userpatches/{config-example.conf,config-docker.conf,config-vagrant.conf} 1> /dev/null 2>&1; then
 
 	# Migrate old configs
-	if ls ${SRC}/*.conf 1> /dev/null 2>&1; then
+	if ls "${SRC}"/*.conf 1> /dev/null 2>&1; then
 		display_alert "Migrate config files to userpatches directory" "all *.conf" "info"
                 cp "${SRC}"/*.conf "${SRC}"/userpatches  || exit 1
 		rm "${SRC}"/*.conf
@@ -188,36 +192,36 @@ if ! ls ${SRC}/userpatches/{config-example.conf,config-docker.conf,config-vagran
 
 fi
 
-if [[ -z "$CONFIG" && -n "$1" && -f "${SRC}/userpatches/config-$1.conf" ]]; then
+if [[ -z "${CONFIG}" && -n "$1" && -f "${SRC}/userpatches/config-$1.conf" ]]; then
 	CONFIG="userpatches/config-$1.conf"
 	shift
 fi
 
 # usind default if custom not found
-if [[ -z "$CONFIG" && -f "${SRC}/userpatches/config-default.conf" ]]; then
+if [[ -z "${CONFIG}" && -f "${SRC}/userpatches/config-default.conf" ]]; then
 	CONFIG="userpatches/config-default.conf"
 fi
 
 # source build configuration file
-CONFIG_FILE="$(realpath "$CONFIG")"
+CONFIG_FILE="$(realpath "${CONFIG}")"
 
-if [[ ! -f $CONFIG_FILE ]]; then
-	display_alert "Config file does not exist" "$CONFIG" "error"
+if [[ ! -f "${CONFIG_FILE}" ]]; then
+	display_alert "Config file does not exist" "${CONFIG}" "error"
 	exit 254
 fi
 
-CONFIG_PATH=$(dirname "$CONFIG_FILE")
+CONFIG_PATH=$(dirname "${CONFIG_FILE}")
 
-display_alert "Using config file" "$CONFIG_FILE" "info"
-pushd $CONFIG_PATH > /dev/null
+display_alert "Using config file" "${CONFIG_FILE}" "info"
+pushd "${CONFIG_PATH}" > /dev/null || exit
 # shellcheck source=/dev/null
-source "$CONFIG_FILE"
-popd > /dev/null
+source "${CONFIG_FILE}"
+popd > /dev/null || exit
 
-[[ -z "${USERPATCHES_PATH}" ]] && USERPATCHES_PATH="$CONFIG_PATH"
+[[ -z "${USERPATCHES_PATH}" ]] && USERPATCHES_PATH="${CONFIG_PATH}"
 
 # Script parameters handling
-while [[ $1 == *=* ]]; do
+while [[ "${1}" == *=* ]]; do
     parameter=${1%%=*}
     value=${1##*=}
     shift
@@ -225,7 +229,7 @@ while [[ $1 == *=* ]]; do
     eval "$parameter=\"$value\""
 done
 
-if [[ $BUILD_ALL == yes || $BUILD_ALL == demo ]]; then
+if [[ "${BUILD_ALL}" == "yes" || "${BUILD_ALL}" == "demo" ]]; then
 	# shellcheck source=lib/build-all-ng.sh
 	source "${SRC}"/lib/build-all-ng.sh
 else
diff --git a/lib/fel-load.sh b/lib/fel-load.sh
index e40ffd904..d0f918e7c 100644
--- a/lib/fel-load.sh
+++ b/lib/fel-load.sh
@@ -16,14 +16,14 @@
 fel_prepare_host()
 {
 	# Start rpcbind for NFS if inside docker container
-	[ `systemd-detect-virt` == 'docker' ] && service rpcbind start
+	[ "$(systemd-detect-virt)" == 'docker' ] && service rpcbind start
 
 	# remove and re-add NFS share
 	rm -f /etc/exports.d/armbian.exports
 	mkdir -p /etc/exports.d
 	echo "$FEL_ROOTFS *(rw,async,no_subtree_check,no_root_squash,fsid=root)" > /etc/exports.d/armbian.exports
 	# Start NFS server if inside docker container
-	[ `systemd-detect-virt` == 'docker' ] && service nfs-kernel-server start
+	[ "$(systemd-detect-virt)" == 'docker' ] && service nfs-kernel-server start
 	exportfs -ra
 }
 
@@ -70,7 +70,7 @@ fel_load()
 	[[ $(type -t fel_pre_load) == function ]] && fel_pre_load
 
 	display_alert "Loading files via" "FEL USB" "info"
-	sunxi-fel ${FEL_EXTRA_ARGS} -p uboot "${FEL_ROOTFS}/usr/lib/${CHOSEN_UBOOT}_${REVISION}_armhf/u-boot-sunxi-with-spl.bin" \
+	sunxi-fel "${FEL_EXTRA_ARGS}" -p uboot "${FEL_ROOTFS}/usr/lib/${CHOSEN_UBOOT}_${REVISION}_armhf/u-boot-sunxi-with-spl.bin" \
 		write 0x42000000 "${FEL_ROOTFS}"/boot/zImage \
 		write 0x43000000 "${FEL_ROOTFS}/${dtb_file}" \
 		write 0x43300000 "${FEL_ROOTFS}"/boot/uInitrd \
diff --git a/lib/main.sh b/lib/main.sh
index d007f4363..26ec536d6 100644
--- a/lib/main.sh
+++ b/lib/main.sh
@@ -24,7 +24,7 @@ fi
 umask 002
 
 # destination
-DEST=$SRC/output
+DEST="${SRC}"/output
 
 if [[ $BUILD_ALL != "yes" ]]; then
 	# override stty size
@@ -113,9 +113,9 @@ if [[ -n $REPOSITORY_UPDATE ]]; then
         fi
 
         # For user override
-        if [[ -f $USERPATCHES_PATH/lib.config ]]; then
+        if [[ -f "${USERPATCHES_PATH}"/lib.config ]]; then
                 display_alert "Using user configuration override" "userpatches/lib.config" "info"
-            source "$USERPATCHES_PATH"/lib.config
+            source "${USERPATCHES_PATH}"/lib.config
         fi
 
         repo-manipulate "$REPOSITORY_UPDATE"
@@ -373,12 +373,12 @@ else
 fi
 
 branch2dir() {
-	[[ $1 == head ]] && echo HEAD || echo ${1##*:}
+	[[ "${1}" == "head" ]] && echo "HEAD" || echo "${1##*:}"
 }
 
-BOOTSOURCEDIR=$BOOTDIR/$(branch2dir ${BOOTBRANCH})
-LINUXSOURCEDIR=$KERNELDIR/$(branch2dir ${KERNELBRANCH})
-[[ -n $ATFSOURCE ]] && ATFSOURCEDIR=$ATFDIR/$(branch2dir ${ATFBRANCH})
+BOOTSOURCEDIR="${BOOTDIR}/$(branch2dir "${BOOTBRANCH}")"
+LINUXSOURCEDIR="${KERNELDIR}/$(branch2dir "${KERNELBRANCH}")"
+[[ -n $ATFSOURCE ]] && ATFSOURCEDIR="${ATFDIR}/$(branch2dir "${ATFBRANCH}")"
 
 # define package names
 DEB_BRANCH=${BRANCH//default}
@@ -450,7 +450,7 @@ if [[ ! -f ${DEB_STORAGE}/armbian-config_${REVISION}_all.deb ]]; then
 fi
 
 # Compile armbian-firmware if packed .deb does not exist or use the one from repository
-if ! ls ${DEB_STORAGE}/armbian-firmware_${REVISION}_all.deb 1> /dev/null 2>&1 || ! ls ${DEB_STORAGE}/armbian-firmware-full_${REVISION}_all.deb 1> /dev/null 2>&1; then
+if ! ls "${DEB_STORAGE}/armbian-firmware_${REVISION}_all.deb" 1> /dev/null 2>&1 || ! ls "${DEB_STORAGE}/armbian-firmware-full_${REVISION}_all.deb" 1> /dev/null 2>&1; then
 
 	if [[ "${REPOSITORY_INSTALL}" != *armbian-firmware* ]]; then
 
@@ -493,7 +493,7 @@ runtime=$(((end-start)/60))
 display_alert "Runtime" "$runtime min" "info"
 
 # Make it easy to repeat build by displaying build options used
-[ `systemd-detect-virt` == 'docker' ] && BUILD_CONFIG='docker'
+[ "$(systemd-detect-virt)" == 'docker' ] && BUILD_CONFIG='docker'
 display_alert "Repeat Build Options" "./compile.sh ${BUILD_CONFIG} BOARD=${BOARD} BRANCH=${BRANCH} \
 $([[ -n $RELEASE ]] && echo "RELEASE=${RELEASE} ")\
 $([[ -n $BUILD_MINIMAL ]] && echo "BUILD_MINIMAL=${BUILD_MINIMAL} ")\