diff --git a/tools/osbuilder/initrd-builder/initrd_builder.sh b/tools/osbuilder/initrd-builder/initrd_builder.sh
index f3c1c2883a..8b8d88bc87 100755
--- a/tools/osbuilder/initrd-builder/initrd_builder.sh
+++ b/tools/osbuilder/initrd-builder/initrd_builder.sh
@@ -4,22 +4,25 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-[ -z "${DEBUG}" ] || set -x
+[[ -z "${DEBUG}" ]] || set -x
 
 set -o errexit
 # set -o nounset
 set -o pipefail
 
 script_name="${0##*/}"
-script_dir="$(dirname $(readlink -f $0))"
+script_dir="$(dirname "$(readlink -f "$0")")"
 
 lib_file="${script_dir}/../scripts/lib.sh"
-source "$lib_file"
+# shellcheck source=../scripts/lib.sh
+# shellcheck disable=SC1091
+source "${lib_file}"
 
 INITRD_IMAGE="${INITRD_IMAGE:-kata-containers-initrd.img}"
 AGENT_BIN=${AGENT_BIN:-kata-agent}
 AGENT_INIT=${AGENT_INIT:-no}
 
+# shellcheck disable=SC2120
 usage()
 {
 	error="${1:-0}"
@@ -44,41 +47,43 @@ exit "${error}"
 
 while getopts "ho:" opt
 do
-	case "$opt" in
+	case "${opt}" in
 		h)	usage ;;
 		o)	INITRD_IMAGE="${OPTARG}" ;;
+		*)	usage 1 ;;
 	esac
 done
 
-shift $(( $OPTIND - 1 ))
+shift $(( OPTIND - 1 ))
 
 ROOTFS="$1"
 
 
-[ -n "${ROOTFS}" ] || usage
-[ -d "${ROOTFS}" ] || die "${ROOTFS} is not a directory"
+# shellcheck disable=SC2119
+[[ -n "${ROOTFS}" ]] || usage
+[[ -d "${ROOTFS}" ]] || die "${ROOTFS} is not a directory"
 
-ROOTFS=$(readlink -f ${ROOTFS})
-IMAGE_DIR=$(dirname ${INITRD_IMAGE})
-IMAGE_DIR=$(readlink -f ${IMAGE_DIR})
-IMAGE_NAME=$(basename ${INITRD_IMAGE})
+ROOTFS=$(readlink -f "${ROOTFS}")
+IMAGE_DIR=$(dirname "${INITRD_IMAGE}")
+IMAGE_DIR=$(readlink -f "${IMAGE_DIR}")
+IMAGE_NAME=$(basename "${INITRD_IMAGE}")
 
 # The kata rootfs image expects init to be installed
 init="${ROOTFS}/sbin/init"
-[ -x "${init}" ] || [ -L ${init} ] || die "/sbin/init is not installed in ${ROOTFS}"
+[[ -x "${init}" ]] || [[ -L "${init}" ]] || die "/sbin/init is not installed in ${ROOTFS}"
 OK "init is installed"
-[ "${AGENT_INIT}" == "yes" ] || [ -x "${ROOTFS}/usr/bin/${AGENT_BIN}" ] || \
+[[ "${AGENT_INIT}" == "yes" ]] || [[ -x "${ROOTFS}/usr/bin/${AGENT_BIN}" ]] || \
 	die "/usr/bin/${AGENT_BIN} is not installed in ${ROOTFS}
 	use AGENT_BIN env variable to change the expected agent binary name"
 OK "Agent is installed"
 
 # initramfs expects /init, create symlink only if ${ROOTFS}/init does not exist
 # Init may be provided by other packages, e.g. systemd or GPU initrd/rootfs
-if [ ! -x "${ROOTFS}/init" ] && [ ! -L "${ROOTFS}/init" ]; then
+if [[ ! -x "${ROOTFS}/init" ]] && [[ ! -L "${ROOTFS}/init" ]]; then
   # ATTN: In some instances, /init is not following two or more levels of symlinks
   # i.e. (/init to /sbin/init to /lib/systemd/systemd)
   # Setting /init directly to /lib/systemd/systemd when AGENT_INIT is disabled
-  if [ "${AGENT_INIT}" = "yes" ]; then
+  if [[ "${AGENT_INIT}" = "yes" ]]; then
     sudo ln -sf /sbin/init "${ROOTFS}/init"
   else
     sudo ln -sf /lib/systemd/systemd "${ROOTFS}/init"