diff --git a/0_nfs.sh b/0_nfs.sh
index b19979a..352e45a 100755
--- a/0_nfs.sh
+++ b/0_nfs.sh
@@ -1,6 +1,11 @@
 #!/bin/bash
 #
 
+if [ "$EUID" -ne 0 ]; then
+    echo "This script must be run as root." >&2
+    exit 1
+fi
+
 export DEBIAN_FRONTEND=noninteractive
 apt update -qy
 apt -qy install nfs-common
diff --git a/1_setup_docker_apt_repo.sh b/1_setup_docker_apt_repo.sh
index 3b1c6a6..1827b8c 100755
--- a/1_setup_docker_apt_repo.sh
+++ b/1_setup_docker_apt_repo.sh
@@ -1,5 +1,10 @@
 #!/bin/bash
 
+if [ "$EUID" -ne 0 ]; then
+    echo "This script must be run as root." >&2
+    exit 1
+fi
+
 # REF:https://docs.docker.com/engine/install/debian/#install-using-the-repository
 
 # Add Docker's official GPG key:
diff --git a/2_install_docker_pkgs.sh b/2_install_docker_pkgs.sh
index 2d3cf35..e43ff75 100755
--- a/2_install_docker_pkgs.sh
+++ b/2_install_docker_pkgs.sh
@@ -1,3 +1,8 @@
 #!/bin/bash
 
+if [ "$EUID" -ne 0 ]; then
+    echo "This script must be run as root." >&2
+    exit 1
+fi
+
 apt install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
diff --git a/3_users.sh b/3_users.sh
index f858d86..685ddb1 100755
--- a/3_users.sh
+++ b/3_users.sh
@@ -1,5 +1,10 @@
 #!/bin/bash
 
+if [ "$EUID" -ne 0 ]; then
+    echo "This script must be run as root." >&2
+    exit 1
+fi
+
 grep jenkins /etc/group >/dev/null 2>&1 || groupadd jenkins && echo 'jenkins group exists'
 grep jenkins /etc/passwd >/dev/null 2>&1 || useradd jenkins -g jenkins -G docker -m && echo 'jenkins user exists'
 
diff --git a/4_provision_networks.sh b/4_provision_networks.sh
index eb2579c..9bcefe8 100755
--- a/4_provision_networks.sh
+++ b/4_provision_networks.sh
@@ -1,5 +1,10 @@
 #!/usr/bin/env bash
 
+if [ "$EUID" -ne 0 ]; then
+    echo "This script must be run as root." >&2
+    exit 1
+fi
+
 ip link set eth0 promisc on
 
 docker network inspect infra_dev_net >/dev/null 2>&1 || \
diff --git a/5_config_docker.sh b/5_config_docker.sh
index 3bab2a1..eaa34d0 100755
--- a/5_config_docker.sh
+++ b/5_config_docker.sh
@@ -1,5 +1,10 @@
 #!/usr/bin/env bash
 
+if [ "$EUID" -ne 0 ]; then
+    echo "This script must be run as root." >&2
+    exit 1
+fi
+
 mkdir -p /etc/docker
 
 cat << EOF >> /etc/docker/daemon.json
diff --git a/99_upgrade.sh b/99_upgrade.sh
index 9cdf312..0b1921e 100755
--- a/99_upgrade.sh
+++ b/99_upgrade.sh
@@ -1,4 +1,10 @@
 #!/bin/bash
+
+if [ "$EUID" -ne 0 ]; then
+    echo "This script must be run as root." >&2
+    exit 1
+fi
+
 export DEBIAN_FRONTEND=noninteractive
 
 apt update -qy