diff --git a/usr/local/bin/disk_space_alert b/usr/local/bin/disk_space_alert
index 0935018..f4e6d93 100755
--- a/usr/local/bin/disk_space_alert
+++ b/usr/local/bin/disk_space_alert
@@ -13,11 +13,6 @@ EOF
 
 set -e;
 
-HOSTNAME=$(hostname)
-DISK_SPACE_ALERT_MAIL_ADDRESS="";
-DISK_SPACE_ALERT_THRESHOLD=93
-DISK_SPACE_ALERT_MOUNTPOINTS=("/")
-
 # check for config file
 apply_config() {
   local config=$1;
@@ -55,7 +50,20 @@ source_config() {
     return;
   fi
 }
+
+check_required() {
+  type hostname &> /dev/null || { echo "Requiring 'hostname' but it's not installed"; exit 1; }
+  type mailx &> /dev/null || { echo "Requiring 'mailx' but it's not installed"; exit 1; }
+  type df &> /dev/null || { echo "Requiring 'df' but it's not installed"; exit 1; }
+}
+
 source_config "$1" "$HOME/.disk_space_alert.conf" "/etc/disk_space_alert.conf"
+check_required
+
+HOSTNAME=$(hostname)
+DISK_SPACE_ALERT_MAIL_ADDRESS="";
+DISK_SPACE_ALERT_THRESHOLD=93
+DISK_SPACE_ALERT_MOUNTPOINTS=("/")
 
 for point in "${DISK_SPACE_ALERT_MOUNTPOINTS[@]}"
 do
diff --git a/usr/local/bin/docker_check b/usr/local/bin/docker_check
index 79fa4e9..08032ce 100755
--- a/usr/local/bin/docker_check
+++ b/usr/local/bin/docker_check
@@ -13,7 +13,6 @@ EOF
 
 set -e;
 
-HOSTNAME=$(hostname)
 DOCKER_CHECK_LIST_FILE="$HOME/.docker_check.list"
 DOCKER_CHECK_GLOBAL_LIST_FILE="/etc/docker_check.list"
 DOCKER_CHECK_NOTIFY_LEVELS=("UNKNOWN" "WARNING" "CRITICAL")
@@ -58,7 +57,17 @@ source_config() {
     return;
   fi
 }
+
+check_required() {
+  type hostname &> /dev/null || { echo "Requiring 'hostname' but it's not installed"; exit 1; }
+  type mailx &> /dev/null || { echo "Requiring 'mailx' but it's not installed"; exit 1; }
+  type docker &> /dev/null || { echo "Requiring 'docker' but it's not installed"; exit 1; }
+}
+
 source_config "$1" "$HOME/.docker_check.conf" "/etc/docker_check.conf"
+check_required
+
+HOSTNAME=$(hostname)
 
 listFileToUse=""
 if [[ -f "$DOCKER_CHECK_LIST_FILE" ]]; then
diff --git a/usr/local/bin/docker_compose_update b/usr/local/bin/docker_compose_update
index 39b3a5b..d9bf3df 100755
--- a/usr/local/bin/docker_compose_update
+++ b/usr/local/bin/docker_compose_update
@@ -67,6 +67,8 @@ check_required() {
     	echo "DOCKER_COMPOSE_UPDATE_COMMAND is required"
         exit 1;
     fi
+
+	type docker-compose &> /dev/null || { echo "Requiring 'docker-compose' but it's not installed"; exit 1; }
 }
 
 # check requirements
diff --git a/usr/local/bin/docker_housekeeping b/usr/local/bin/docker_housekeeping
index 725e9b7..94c33eb 100755
--- a/usr/local/bin/docker_housekeeping
+++ b/usr/local/bin/docker_housekeeping
@@ -1,5 +1,12 @@
 #!/usr/bin/env bash
 
+check_required() {
+  type docker &> /dev/null || { echo "Requiring 'docker' but it's not installed"; exit 1; }
+  type yes &> /dev/null || { echo "Requiring 'yes' but it's not installed"; exit 1; }
+}
+
+check_required
+
 echo "Doing docker housekeeping for containers, images and volumes";
 
 yes | docker container prune
diff --git a/usr/local/bin/dynv6 b/usr/local/bin/dynv6
index 4c4ab88..b66105f 100755
--- a/usr/local/bin/dynv6
+++ b/usr/local/bin/dynv6
@@ -82,6 +82,12 @@ check_required() {
       echo "DYNV6_HOSTNAME is required"
       exit 1;
     fi
+
+    type hostname &> /dev/null || { echo "Requiring 'hostname' but it's not installed"; exit 1; }
+    type mailx &> /dev/null || { echo "Requiring 'mailx' but it's not installed"; exit 1; }
+    type ip &> /dev/null || { echo "Requiring 'ip' but it's not installed"; exit 1; }
+    type grep &> /dev/null || { echo "Requiring 'grep' but it's not installed"; exit 1; }
+    type curl &> /dev/null || { echo "Requiring 'curl' but it's not installed"; exit 1; }
 }
 
 # check requirements
diff --git a/usr/local/bin/memory_usage_alert b/usr/local/bin/memory_usage_alert
index 47e852f..ab827e7 100755
--- a/usr/local/bin/memory_usage_alert
+++ b/usr/local/bin/memory_usage_alert
@@ -13,8 +13,6 @@ EOF
 
 set -e;
 
-HOSTNAME=$(hostname)
-SUBJECT="[memory $HOSTNAME] memory is low"
 MEMORY_USAGE_ALERT_MAIL_ADDRESS="";
 MEMORY_USAGE_ALERT_THRESHOLD=512;
 
@@ -56,7 +54,17 @@ source_config() {
   fi
 }
 
+check_required() {
+  type hostname &> /dev/null || { echo "Requiring 'hostname' but it's not installed"; exit 1; }
+  type mailx &> /dev/null || { echo "Requiring 'mailx' but it's not installed"; exit 1; }
+  type free &> /dev/null || { echo "Requiring 'free' but it's not installed"; exit 1; }
+}
+
 source_config "$1" "$HOME/.memory_usage_alert.conf" "/etc/memory_usage_alert.conf"
+check_required
+
+HOSTNAME=$(hostname)
+SUBJECT="[memory $HOSTNAME] memory is low"
 
 # DO NOT TOUCH BELOW
 total=$(free -mt | grep Total | awk '{print $2}')
diff --git a/usr/local/bin/perms_default_umask b/usr/local/bin/perms_default_umask
index fc0caae..e5a0594 100755
--- a/usr/local/bin/perms_default_umask
+++ b/usr/local/bin/perms_default_umask
@@ -6,6 +6,13 @@
 # - align with umask 022 (755 on folders, 644 on files)
 # - keep +x flag for already executable files if enabled (default)
 
+check_required() {
+  type find &> /dev/null || { echo "Requiring 'find' but it's not installed"; exit 1; }
+  type chmod &> /dev/null || { echo "Requiring 'chmod' but it's not installed"; exit 1; }
+}
+
+check_required
+
 DIR="$1"
 KEEP_EXECUTABLE_FILES="$2"
 
diff --git a/usr/local/bin/perms_user_home_default_umask b/usr/local/bin/perms_user_home_default_umask
index e315ccf..9e59e9e 100755
--- a/usr/local/bin/perms_user_home_default_umask
+++ b/usr/local/bin/perms_user_home_default_umask
@@ -7,6 +7,13 @@
 # - keep +x flag for already executable files if enabled (default, otherwise set to no)
 # - set 700 (only allow owner to go into directory)
 
+check_required() {
+  type find &> /dev/null || { echo "Requiring 'find' but it's not installed"; exit 1; }
+  type chmod &> /dev/null || { echo "Requiring 'chmod' but it's not installed"; exit 1; }
+}
+
+check_required
+
 DIR="$1"
 KEEP_EXECUTABLE_FILES="$2"
 
diff --git a/usr/local/bin/smartctl_tests_long b/usr/local/bin/smartctl_tests_long
index ffc1462..198ff1c 100755
--- a/usr/local/bin/smartctl_tests_long
+++ b/usr/local/bin/smartctl_tests_long
@@ -22,7 +22,6 @@ EOF
 
 set -e;
 
-HOSTNAME=$(hostname)
 SMARTCTL_TESTS_LONG_MAIL_ADDRESS="";
 SMARTCTL_TESTS_LONG_DEVICES=(sda)
 
@@ -63,8 +62,17 @@ source_config() {
     return;
   fi
 }
+
+check_required() {
+  type hostname &> /dev/null || { echo "Requiring 'hostname' but it's not installed"; exit 1; }
+  type mailx &> /dev/null || { echo "Requiring 'mailx' but it's not installed"; exit 1; }
+  type smartctl &> /dev/null || { echo "Requiring 'smartctl' but it's not installed"; exit 1; }
+}
+
 source_config "$1" "$HOME/.smartctl_tests_long.conf" "/etc/smartctl_tests_long.conf"
 
+HOSTNAME=$(hostname)
+
 echo "Starting long tests for ...";
 
 for d in "${SMARTCTL_TESTS_LONG_DEVICES[@]}"; do
diff --git a/usr/local/bin/smartdnotify b/usr/local/bin/smartdnotify
index d4b8b96..c5e760f 100755
--- a/usr/local/bin/smartdnotify
+++ b/usr/local/bin/smartdnotify
@@ -1,5 +1,13 @@
 #!/usr/bin/env bash
 
+check_required() {
+  type hostname &> /dev/null || { echo "Requiring 'hostname' but it's not installed"; exit 1; }
+  type mailx &> /dev/null || { echo "Requiring 'mailx' but it's not installed"; exit 1; }
+  type wall &> /dev/null || { echo "Requiring 'wall' but it's not installed"; exit 1; }
+}
+
+check_required
+
 HOSTNAME=$(hostname)
 echo "$SMARTD_MESSAGE" | mail -s "[smartd $HOSTNAME] $SMARTD_FAILTYPE" "$SMARTD_ADDRESS"
 wall "$SMARTD_MESSAGE"
\ No newline at end of file
diff --git a/usr/local/bin/ssh-keygen-rsa b/usr/local/bin/ssh-keygen-rsa
index 2255852..d00262c 100755
--- a/usr/local/bin/ssh-keygen-rsa
+++ b/usr/local/bin/ssh-keygen-rsa
@@ -2,6 +2,11 @@
 
 set -e;
 
+check_required() {
+  type openssl &> /dev/null || { echo "Requiring 'openssl' but it's not installed"; exit 1; }
+  type ssh-keygen &> /dev/null || { echo "Requiring 'ssh-keygen' but it's not installed"; exit 1; }
+}
+
 name=$1;
 encryption=$2;
 
@@ -14,5 +19,7 @@ if [[ -z ${encryption} ]]; then
 	encryption=4096;
 fi
 
+check_required
+
 openssl genrsa -out "${name}" "${encryption}"
 ssh-keygen -y -f "${name}" > "${name}.pub"
\ No newline at end of file
diff --git a/usr/local/bin/systemd_check b/usr/local/bin/systemd_check
index e8e7f26..694c9fc 100755
--- a/usr/local/bin/systemd_check
+++ b/usr/local/bin/systemd_check
@@ -19,8 +19,6 @@ SYSTEMD_CHECK_LIST_FILE="$HOME/.systemd_check.list"
 SYSTEMD_CHECK_GLOBAL_LIST_FILE="/etc/systemd_check.list"
 SYSTEMD_CHECK_MAIL_ENABLED=fase
 SYSTEMD_CHECK_MAIL_ADDRESS=""
-SYSTEMD_CHECK_HOSTNAME=$(hostname)
-SYSTEMD_CHECK_USER=$(whoami)
 SYSTEMD_CHECK_SERVICES=()
 
 # check for config file
@@ -60,7 +58,19 @@ source_config() {
     return;
   fi
 }
+
+check_required() {
+  type hostname &> /dev/null || { echo "Requiring 'hostname' but it's not installed"; exit 1; }
+  type mailx &> /dev/null || { echo "Requiring 'mailx' but it's not installed"; exit 1; }
+  type whoami &> /dev/null || { echo "Requiring 'whoami' but it's not installed"; exit 1; }
+  type systemctl &> /dev/null || { echo "Requiring 'systemctl' but it's not installed"; exit 1; }
+}
+
 source_config "$1" "$HOME/.systemd_check.conf" "/etc/systemd_check.conf"
+check_required
+
+SYSTEMD_CHECK_HOSTNAME=$(hostname)
+SYSTEMD_CHECK_USER=$(whoami)
 
 listFileToUse=""
 if [[ -f "$SYSTEMD_CHECK_LIST_FILE" ]]; then
diff --git a/usr/local/bin/systemd_failure_notify b/usr/local/bin/systemd_failure_notify
index ef096ae..f9f513c 100755
--- a/usr/local/bin/systemd_failure_notify
+++ b/usr/local/bin/systemd_failure_notify
@@ -58,6 +58,8 @@ check_requirements() {
 	if [[ "${gotifyEnabled}" == "true" ]]; then
     type gotify &> /dev/null || { echo "Requiring 'gotify' but it's not installed"; exit 1; }
 	fi
+
+  type whoami &> /dev/null || { echo "Requiring 'whoami' but it's not installed"; exit 1; }
 }
 
 source_config() {