Problems with Checkmk

Here at Sirius, we often get asked, "What are the problems with Checkmk?" This is a very good question, and one that deserves a clear, honest answer. We understand that no technology is perfect, and businesses need to be aware of potential challenges before making a long-term commitment.

We want to be upfront: Checkmk is a powerful and widely adopted IT monitoring system, known for its extensive features, automation capabilities, and high scalability, serving over 2,000 commercial customers and numerous Open Source users. However, like any sophisticated enterprise-grade solution, it comes with its own set of complexities and criticisms that prospective and current users must navigate. The truth is, many perceived "problems" are often inherent trade-offs for its advanced capabilities and architectural design, rather than simple flaws.

This article will deconstruct the common challenges and criticisms associated with Checkmk, helping you understand its nuances and ultimately decide if it aligns with your specific needs. We aim to be fiercely transparent, allowing you to make the most informed decision possible.

The User Experience Paradox: Ease of Setup vs. Steep Learning Curve

A significant and often contradictory theme in user feedback regarding Checkmk is the simultaneous praise for its ease of use and criticism of its difficult learning curve. This apparent paradox stems directly from the product's architectural design, which prioritizes enterprise-scale management through sophisticated, rule-based configurations.

The Illusion of Effortless Onboarding

Checkmk's initial setup is genuinely streamlined and intuitive, promising a fast time-to-value, often allowing a user to monitor their first host in under five minutes. This is achieved through auto-discovery and auto-registration features that automatically configure hosts and services upon agent installation. User reviews support this, with Checkmk scoring highly on "ease of setup" compared to competitors like Prometheus and Datadog. For quick deployments, this immediate positive feedback is a clear strength, as it validates the product's utility without demanding prior expertise.

The Reality of Navigational and Configurational Complexity

Despite the easy start, frustration can arise when users attempt to move beyond basic monitoring. User reviews consistently highlight a "steep learning curve" and a "complex configuration process" that can be "overwhelming and confusing for newcomers". Complaints also point to a "confusing" user interface, making it difficult to "locate settings and navigate effectively". These frustrations are not due to a lack of functionality, but rather the inherent complexity of Checkmk's underlying architecture, requiring users to acquire a new, specific skill set to transition from automated setup to granular fine-tuning.

Rule-Based Configuration: A Double-Edged Sword

The fundamental cause of this perceived complexity is Checkmk's rule-based configuration system. Designed to manage environments with "very many hosts," it employs a sophisticated system of host tags and folder hierarchies. Instead of configuring each service individually—a simple but unscalable task—Checkmk requires users to conceptualize and apply rules that inherit settings across thousands of hosts. While this powerful abstraction allows setting "thresholds for thousands of file systems with a single action", it creates significant cognitive friction for new users. The challenge is not just finding a menu item, but understanding how rules apply and which more specific rules might override them. This configuration philosophy is essential for enterprise scalability but presents a high barrier to entry for those accustomed to simpler, host-by-host configurations.

Technical and Operational Friction Points

Beyond the conceptual challenges, Checkmk users also face concrete technical and operational issues that can cause friction and necessitate manual intervention. These are demonstrable software instabilities and workflow shortcomings.

A Catalog of Recurring Bugs and Glitches

Community forums and user reports reveal a persistent stream of bugs and glitches across various Checkmk versions. These can compromise system reliability and hinder deployment. Examples include:

• Agent and Plugin Management: Issues like the "Agent Updater not installing" or "plugins not being picked up" after updates.
• REST API: Reports of "REST API URL returning 404" errors and a bug where changes could not be activated via the API.
• Upgrade Processes: Problems such as "graph colors are slightly wrong/changed" after an upgrade.
• Specific Checks and Integrations: Bugs like "ZFS monitoring is still broken" and issues in PostgreSQL Bloat calculation.

The presence of these recurring bugs indicates that significant administrative effort may be dedicated to troubleshooting and maintaining the monitoring system itself, which can contradict the goal of reducing operational overhead.

Performance and Scalability: The Devil in the Details

While Checkmk is marketed as "Massively scalable" with a "High Performance Core" for hundreds of thousands of hosts and millions of services, performance bottlenecks can still arise at the host level. For instance, users have reported "timeout after 110 seconds" during service discovery, attributed to slow special agent responses on complex hosts like Proxmox. This demonstrates that while the core can handle vast numbers of checks, the performance of a single, complex check can be a point of failure.

Additionally, high CPU usage of the Checkmk micro core (cmc) is a recognized issue, often requiring increased memory and CPU cores or adjusted VM CPU emulation settings. This indicates that the "High Performance Core" is not a universal solution; its performance is heavily dependent on sufficient resource allocation and can become a bottleneck with computationally intensive checks. Scaling Checkmk, therefore, is not a simple linear process but demands careful planning and a deep understanding of resource demands for specific integrations.

API Limitations and Versioning Challenges

For automation-focused organizations, the REST API is critical. Checkmk offers a well-documented API, but its versioning scheme and functional reliability have been sources of user frustration. The API's separate versioning from the main software can lead to "breaking changes" and compatibility issues between releases. A long-standing bug with the fix_all mode for service discovery, where advertised functionality did not match actual behavior, forced teams to rely on manual workarounds, eroding user trust.

The Acknowledgment and Notification Workflow

Even core functionalities can encounter friction. Despite robust features for acknowledging problems and suppressing notifications, users have reported "Still getting email alerts after acknowledging host AND service". Another issue involves notification rules not taking effect until a manual "apply" action, which was not intuitive for the specific configuration. These seemingly minor issues can significantly impact IT team workflows. When a monitoring system fails to reliably manage notifications, it can lead to "false alarms"—a phenomenon the documentation itself identifies as "fatal to any monitoring". This operational friction erodes confidence and can lead to alert fatigue, compromising an organization's ability to respond to genuine problems.

A Comparative Disadvantage: Checkmk vs. Competitors

While Checkmk is a formidable monitoring solution, it faces certain comparative disadvantages when measured against cloud-native and modern observability platforms like Prometheus and Datadog. User reviews consistently highlight areas where competitors are perceived to have distinct advantages.

The Perception of Performance and Visualization

Checkmk's performance metrics and visualization capabilities are often rated lower by users on G2 compared to Prometheus and Datadog.

• Real-time Monitoring: Prometheus is rated higher (9.6 vs. Checkmk's 7.7).
• Performance Monitoring: Datadog scores higher (9.2 vs. 8.4).
• Data Visualization: Datadog scores higher (9.0 vs. 8.0).

A user review explicitly states that while Checkmk is "great at getting data," its "Data Insights are limited enough" and "customizing Graphs is hard and requires a lot of programming knowledge". This suggests Checkmk excels as a *monitoring* tool focused on data collection and state-based alerting, but it may not be a leader in the modern *observability* space, particularly in transforming data into rich, intuitive, and real-time insights that its competitors excel at.

The Agent-Based vs. Agentless Debate

Checkmk primarily relies on a lightweight, agent-based model for deep system visibility, though it also supports agentless monitoring via SNMP and IPMI. This design choice can be a point of friction for users preferring agentless solutions. For example, Checkmk typically requires an agent to monitor server volumes, whereas Zabbix can pull this information directly via VMware monitoring. This can be perceived as tedious, especially when manual steps like TLS registration are involved. However, it's also noted that Checkmk's agent auto-updates work "99% of the time," significantly reducing long-term administrative overhead compared to manual agent maintenance. The choice between these philosophies is a critical consideration for a systems architect.

The Contradiction in Support and Community

Checkmk's reputation for support is complex. On one hand, G2 users consistently rate Checkmk's "Quality of Support" highly, outscoring Prometheus, Datadog, and Dynatrace. Paid users of the Enterprise Edition praise the official support team for being "quick" and providing "hot fixes".

However, a different picture emerges from broader community platforms, with a Reddit user noting a perceived decline in activity within the r/Sysadmin community regarding Checkmk. This indicates a clear distinction between the highly-rated professional support for commercial products and the organic, informal community surrounding its Open Source version. The perceived lack of a vibrant, public-facing community can be a significant problem for new users and those relying on the free Raw Edition for troubleshooting and advice.

The Historical Security Posture and its Implications

For a Senior Systems Architect, a product's security history is a crucial part of its risk profile. While Checkmk emphasizes features like "granular access control, encryption, and 2FA", it has experienced critical vulnerabilities in the past. A detailed report from a security research firm highlighted a complex, chained remote code execution (RCE) vulnerability that affected Checkmk version 2.1.0p10 and lower.

This exploit was particularly concerning as it leveraged a chain of four individual vulnerabilities, including two rated at 9.1 CVSS. It began with low-impact flaws (SSRF and Line Feed Injection) to forge arbitrary queries, which then facilitated file deletion, authentication bypass, and an authenticated Arbitrary File Read. This access allowed reading a sensitive configuration file, providing credentials for a final Code Injection vulnerability to achieve RCE.

The issues were quickly patched in version 2.1.0p12, with a 24-day timeline from initial report to patched release. While these specific vulnerabilities have been addressed, this incident serves as a powerful reminder:

• Any complex software, especially a high-profile Open Source tool, is susceptible to critical security flaws.
• The onus is on the user to maintain a rigorous and prompt patching strategy to mitigate risk. A delayed or neglected update process can expose an organization to significant and compounding security risks.

This historical event underscores that while Checkmk's development team is responsive, the ultimate responsibility for securing an instance of the software rests with the deploying organization.

Synthesis and Strategic Recommendations

The analysis of Checkmk’s challenges reveals that many are not simple flaws but rather inherent trade-offs of its design. The "steep learning curve" is the cost of its scalable, rule-based configuration system, which is essential for managing large, complex IT environments. Occasional "technical glitches" and "recurring bugs" are functions of a continuously developed product with a vast feature set. Checkmk's comparative disadvantages in real-time monitoring and data visualization are a consequence of its philosophical focus as a comprehensive monitoring solution, rather than a specialized, cloud-native observability platform. Essentially, the product's value and its friction points are two sides of the same coin.

Actionable Recommendations for a Successful Implementation

Based on this comprehensive analysis, a successful Checkmk implementation requires a strategic approach beyond a basic evaluation.

For Evaluation Teams:

• Go Beyond the Trial: Do not base a decision solely on the "5-minute" initial setup. A rigorous evaluation should include testing advanced features and edge cases, such as monitoring complex hosts like Proxmox and configuring specific API workflows.
• Evaluate the Enterprise Edition: For any significant deployment, the included professional support of the Enterprise Edition is a critical asset. The high ratings for Checkmk's official support and the perceived quietness of the broader community forums indicate that paid support can be essential for overcoming technical challenges.
• Investigate the Architectural Fit: Determine if an agent-heavy monitoring approach aligns with your organization's needs. If deep, granular visibility is the goal, Checkmk's agent model is powerful. If a fully agentless setup is a strict requirement, a different solution may be more appropriate.

For Current Users:

• Prioritize a Patching Strategy: Establish a robust and prompt patching and upgrade schedule to mitigate security risks and address functional bugs. The history of security vulnerabilities serves as a clear indicator of the importance of staying current.
• Invest in Training: To unlock the full potential of Checkmk, teams must invest in training to fully grasp the nuances of the rule-based configuration system. Understanding the folder hierarchy and host tags is key to mastering the platform.
• Leverage Official Resources: When encountering issues, prioritize the official documentation, video tutorials, and paid support channels before turning to informal community forums.

Concluding Outlook

Checkmk is a mature and powerful IT monitoring system. Its ability to provide comprehensive, unified visibility across diverse IT infrastructures is a testament to its robust design and continued development. The high rating for its "product direction" at 9.4 on G2 suggests a strong commitment to future improvements and user needs. The problems associated with Checkmk are not insurmountable flaws but rather characteristics of a sophisticated tool that demands a certain level of technical and operational discipline. For an organization prepared to invest in a rigorous implementation and maintenance strategy, Checkmk can provide a scalable, feature-rich solution for modern IT monitoring.