diff --git a/kubernetes/contrib/dns-server-for-vhost-ingress-testing/deploy_dns.sh b/kubernetes/contrib/dns-server-for-vhost-ingress-testing/deploy_dns.sh
index 1a75bd7..67bbfd6 100755
--- a/kubernetes/contrib/dns-server-for-vhost-ingress-testing/deploy_dns.sh
+++ b/kubernetes/contrib/dns-server-for-vhost-ingress-testing/deploy_dns.sh
@@ -86,9 +86,11 @@
 	target_machine_notice_info
 }
 
-if [[ $# -eq 1 ]] && [[ $1 = "-h" || $1 = "--help" ]]; then
+if [ $# -eq 1 ] && [ "$1" = "-h" ]; then
 	usage
-elif [[ $# -eq 1 ]] && [[ $1 = "--info" ]]; then
+elif [ $# -eq 1 ] && [ "$1" = "--help" ]; then
+	usage
+elif [ $# -eq 1 ] && [ "$1" = "--info" ]; then
        target_machine_notice_info
 else
 	deploy $@
diff --git a/kubernetes/contrib/metallb-loadbalancer-inst/install-metallb-on-cluster.sh b/kubernetes/contrib/metallb-loadbalancer-inst/install-metallb-on-cluster.sh
index 44fe79a..bf2bc12 100755
--- a/kubernetes/contrib/metallb-loadbalancer-inst/install-metallb-on-cluster.sh
+++ b/kubernetes/contrib/metallb-loadbalancer-inst/install-metallb-on-cluster.sh
@@ -76,9 +76,11 @@
 	generate_config_map $@
 }
 
-if [[ $# -eq 1 ]] && [[ $1 = "-h" || $1 = "--help" ]]; then
+if [ $# -eq 1 ] && [ "$1" = "-h" ]; then
 	usage
-elif [[ $# -eq 0 ]]; then
+if [ $# -eq 1 ] && [ "$1" = "--help" ]; then
+	usage
+elif [ $# -eq 0 ]; then
 	automatic_configuration
 else
 	manual_configuration $@
diff --git a/kubernetes/contrib/tools/rke/rke_setup.sh b/kubernetes/contrib/tools/rke/rke_setup.sh
index 7950e0c..2ee123b 100755
--- a/kubernetes/contrib/tools/rke/rke_setup.sh
+++ b/kubernetes/contrib/tools/rke/rke_setup.sh
@@ -344,7 +344,7 @@
     esac
 done
 
-if [[ -z $BRANCH ]]; then
+if [ -z $BRANCH ]; then
   usage
   exit 1
 fi
diff --git a/kubernetes/portal/docker/init/mariadb-client/db_migrate.sh b/kubernetes/portal/docker/init/mariadb-client/db_migrate.sh
index 6f62a0e..2b90a99 100644
--- a/kubernetes/portal/docker/init/mariadb-client/db_migrate.sh
+++ b/kubernetes/portal/docker/init/mariadb-client/db_migrate.sh
@@ -17,10 +17,10 @@
 SQL_DEST_DIR=${SQL_DEST_DIR:-/tmp/sql}
 DB_PORT=${DB_PORT:-3306}
 
-[[ -z "$SQL_SRC_DIR" ]] && { echo "Error: SQL_SRC_DIR must be provided as an environment variable"; exit 1; }
-[[ -z "$DB_USER" ]] && { echo "Error: DB_USER must be provided as an environment variable"; exit 1; }
-[[ -z "$DB_PASS" ]] && { echo "Error: DB_PASS must be provided as an environment variable"; exit 1; }
-[[ -z "$DB_HOST" ]] && { echo "Error: DB_HOST must be provided as an environment variable"; exit 1; }
+[ -z "$SQL_SRC_DIR" ] && { echo "Error: SQL_SRC_DIR must be provided as an environment variable"; exit 1; }
+[ -z "$DB_USER" ] && { echo "Error: DB_USER must be provided as an environment variable"; exit 1; }
+[ -z "$DB_PASS" ] && { echo "Error: DB_PASS must be provided as an environment variable"; exit 1; }
+[ -z "$DB_HOST" ] && { echo "Error: DB_HOST must be provided as an environment variable"; exit 1; }
 
 mkdir -p $SQL_DEST_DIR