Add plugin to monitor os release expiry

checkmk/custom-files/local/monitor-os-expiry

+#!/bin/bash
+
+# WARN if less than this amount of days is left on the os release
+CONFIG_WARN_DAYS_LEFT=180
+
+# CRIT if less than this amount of days is left on the os release
+CONFIG_CRIT_DAYS_LEFT=90
+
+# Fetch current time
+NOW=$(date +%s)
+
+# Fetch an easy matchable string that represents the current OS version
+OS=$(lsb_release -i -r | cut -f 2 | tr '\n' ' ')
+
+# Initialize expiredate with marker for unknown OS
+expiredate=-1
+
+# Use bash regex to match OS, assign expiredate in format of "YYYY-MM-DD"
+# NOTE: You have to use [[:space:]] to match spaces because, you know, bash.
+if [[ $OS =~ ^Debian[[:space:]]9 ]]; then
+    expiredate="2022-06-30"
+elif [[ $OS =~ ^Debian[[:space:]]10 ]]; then
+    expiredate="2024-06-30"
+elif [[ $OS =~ ^Debian[[:space:]]11 ]]; then
+    expiredate="2026-06-30"
+elif [[ $OS =~ ^Ubuntu[[:space:]]18\.04 ]]; then
+    expiredate="2023-04-30"
+elif [[ $OS =~ ^Ubuntu[[:space:]]20\.04 ]]; then
+    expiredate="2025-04-30"
+elif [[ $OS =~ ^CentOS[[:space:]]7 ]]; then
+    expiredate="2024-06-30"
+fi
+
+# If OS is not handled yet ...
+if [[ "$expiredate" == "-1" ]]; then
+    # ... report an error, so a dev can extend the plugin
+    echo "3 OS-Expiry - Unknown OS '$OS', please extend agent plugin 'monitor-os-expiry'!"
+else
+    # otherwise, calculate remaining days for OS and report accordingly.
+    os_expire_timestamp=$(date -d "$expiredate" +%s)
+    remaining_seconds=$(($os_expire_timestamp - $NOW))
+    remaining_days=$(($remaining_seconds / 86400))
+    # Default is OK, gets overridden by WARN, then by CRIT
+    checkmk_status="0"
+    if [[ $remaining_days -le $CONFIG_WARN_DAYS_LEFT ]]; then
+        checkmk_status="1"
+    fi
+    if [[ $remaining_days -le $CONFIG_CRIT_DAYS_LEFT ]]; then
+        checkmk_status="2"
+    fi
+    echo "$checkmk_status OS-Expiry - $remaining_days days remaining for $OS)"
+fi
\ No newline at end of file

checkmk/generic/monitor-os-expiry.sls

+hsh_checkmk_monitor_os_expiry_plugin:
+  file.managed:
+    - name: /usr/lib/check_mk_agent/local/monitor-os-expiry
+    - source: salt://checkmk/custom-files/local/monitor-os-expiry
+    - mode: 755
+    - user: root
+    - group: root