diff --git a/nagios/templates/deployment.yaml b/nagios/templates/deployment.yaml
index 6c16264a9..d0f3d35ec 100644
--- a/nagios/templates/deployment.yaml
+++ b/nagios/templates/deployment.yaml
@@ -81,6 +81,8 @@ spec:
         configmap-bin-hash: {{ tuple "configmap-bin.yaml" . | include "helm-toolkit.utils.hash" }}
         configmap-etc-hash: {{ tuple "configmap-etc.yaml" . | include "helm-toolkit.utils.hash" }}
     spec:
+      securityContext:
+        readOnlyRootFilesystem: true
       serviceAccountName: {{ $serviceAccountName }}
       nodeSelector:
         {{ .Values.labels.nagios.node_selector_key }}: {{ .Values.labels.nagios.node_selector_value | quote }}