System Reboot Required – Checkmk 2.4 Plugin

A Checkmk 2.4 MKP plugin that monitors Linux hosts for pending system reboots. It detects whether a reboot is required, how long it has been pending, and which packages triggered it — across all major Linux distributions.

Requires: Checkmk 2.4.0+ (CRE/CEE/CME) · Linux hosts with Checkmk agent · GPLv3 License

---

Features

• Monitors every host with a single service: System Reboot Required
• Reports how long a reboot has been pending with configurable WARN/CRIT thresholds
• Supports all major Linux distributions via multiple detection methods (graceful degradation)
• Shows detection method, time pending, and affected packages in the service summary
• Immediate CRIT when a reboot is required but the pending-since timestamp is unknown

---

Supported Distributions & Detection Methods

Distribution	Detection Method	Details
Debian / Ubuntu	/var/run/reboot-required	Written by apt and unattended-upgrades
Debian / Ubuntu	/var/run/reboot-required.pkgs	Package list that triggered the reboot
Debian / Ubuntu (alt.)	/run/reboot-required	Fallback path on some systems
RHEL / CentOS 7+	needs-restarting -r	Exit code 1 = reboot required
Rocky / AlmaLinux	needs-restarting -r	Same as RHEL
All RPM-based	uname -r vs. rpm -q kernel --last	Detects running kernel ≠ installed kernel

Detection methods are tried in order. If one is unavailable (e.g. needs-restarting not installed), it is skipped silently.

---

Installation

Via Checkmk GUI (recommended)

1. Download system_reboot_required-1.0.0.mkp from the Releases page
2. In Checkmk: Setup → Extension Packages → Upload package
3. Upload the .mkp file and click Install

Via CLI (as site user)

mkp add system_reboot_required-1.0.0.mkp
mkp enable system_reboot_required

Deploy the agent plugin to monitored hosts

The shell script must be installed on each monitored host:

# From the Checkmk site:
scp /omd/sites/<site>/local/share/check_mk/agents/plugins/system_reboot_required \
    root@<host>:/usr/lib/check_mk_agent/plugins/system_reboot_required

chmod 755 /usr/lib/check_mk_agent/plugins/system_reboot_required

Then run a service discovery:

cmk -II <hostname>
cmk -R

---

Configuration

Navigate to Setup → Services → Service monitoring rules → System Reboot Required.

Parameter	Default	Description
WARN after pending reboot for (hours)	12	Turns WARN when reboot has been pending for at least this many hours
CRIT after pending reboot for (hours)	24	Turns CRIT when reboot has been pending for at least this many hours

Note: The CRIT threshold must be ≥ the WARN threshold. If a reboot is pending but the timestamp cannot be determined, the service turns CRIT immediately.

Service states

State	Condition
OK	No reboot pending
OK	Reboot pending for less than WARN threshold
WARN	Reboot pending for ≥ WARN hours
CRIT	Reboot pending for ≥ CRIT hours
CRIT	Reboot required, timestamp unknown
UNKNOWN	No data from agent plugin

---

How It Works

Checkmk Check Cycle
  └─ Agent plugin (shell script on monitored host)
       ├─ Checks /var/run/reboot-required       (Debian/Ubuntu)
       ├─ Reads /var/run/reboot-required.pkgs   (package list)
       ├─ Runs needs-restarting -r              (RHEL/CentOS/Rocky)
       └─ Compares uname -r vs rpm kernel       (RPM fallback)
  └─ Checkmk Section  <<<system_reboot_required>>>
       reboot_required: 1
       detection_method: reboot-required-file
       since_timestamp: <unix timestamp>
       packages: linux-image-generic, linux-headers-generic
  └─ Check plugin (system_reboot_required/agent_based/)
       ├─ Calculates age from timestamp
       └─ Compares against warn_hours / crit_hours thresholds

---

File Structure

system_reboot_required/
├── agent_based/
│   └── system_reboot_required.py   # Check plugin: parse, discover, check
└── rulesets/
    └── system_reboot_required.py   # WATO ruleset: thresholds
agents/
└── plugins/
    └── system_reboot_required      # Shell script (runs on monitored host)

---

Building from Source

Run as root on the Checkmk server:

# Deploy files to site (replace <site> with your site name)
SITE=<site>
install -m 755 agents/plugins/system_reboot_required \
    /omd/sites/$SITE/local/share/check_mk/agents/plugins/system_reboot_required
install -m 644 system_reboot_required/agent_based/system_reboot_required.py \
    /omd/sites/$SITE/local/lib/python3/cmk_addons/plugins/system_reboot_required/agent_based/system_reboot_required.py
install -m 644 system_reboot_required/rulesets/system_reboot_required.py \
    /omd/sites/$SITE/local/lib/python3/cmk_addons/plugins/system_reboot_required/rulesets/system_reboot_required.py

# Build MKP (as site user)
cp packages/system_reboot_required /omd/sites/$SITE/var/check_mk/packages/system_reboot_required
su - $SITE -c "mkp package /omd/sites/$SITE/var/check_mk/packages/system_reboot_required"

The resulting .mkp file will be in /omd/sites/$SITE/var/check_mk/packages_local/.

---

License

GPLv3 — see LICENSE

Author

Luca-Leon Hausdoerfer — github.com/blaugrau90