Moving from CentOS to AlmaLinux or Rocky Linux

Key Takeaways

• Assess workloads, validate hardware, and run application testing in a staging environment before migrating from CentOS to AlmaLinux or Rocky Linux.
• Mitigate risks such as dependency drift, kernel incompatibilities, and application regressions through structured planning and proactive validation.
• Leverage enterprise support, vetted updates, 24/7 break-fix assistance, and compliance guidance to maintain a stable and secure AlmaLinux environment.

For many enterprises, CentOS was a trusted, stable Linux platform for decades. However, following the discontinuation of CentOS 8 in December 2021 and the End-of-Life (EOL) of CentOS 7 in June 2024, organizations must address a critical challenge. Running on unsupported operating systems exposes them to significant security and compliance risks. This drives the need to migrate to a reliable, RHEL-compatible distribution that restores long-term stability and security.

For CentOS users, AlmaLinux has emerged as the preferred enterprise-ready successor. It offers a predictable release cycle, strong community and enterprise backing, and full RHEL application binary (ABI) compatibility, ensuring applications built for RHEL run seamlessly on AlmaLinux.

This article provides a planning and readiness guide for enterprises migrating from CentOS to AlmaLinux (or Rocky Linux). It covers migration readiness, common pitfalls, testing approaches, and post-migration support to help teams make informed decisions and ensure a smooth transition.

Migration Readiness Checklist for Enterprises

Before switching from CentOS (or similar RHEL clones) to AlmaLinux, enterprises must adopt a strategic and methodical approach. A thorough readiness assessment is paramount to ensuring a smooth transition, minimizing downtime, and preventing unexpected post-migration issues. Below are the six key areas every organization must review:

1. Asset and Dependency Discovery

The foundational step is to conduct a detailed, automated inventory of all running workloads on your CentOS servers. This inventory must catalog all applications, services, databases, middleware, custom scripts, and specific package versions. Determining which components are business-critical will help prioritize the migration order and spot potential blockers. Legacy applications, for instance, are often dependent on specific, older libraries that demand meticulous testing before moving to the AlmaLinux environment.

2. Hardware and Kernel Compatibility

Make sure that AlmaLinux fully supports your existing servers, storage arrays, and network hardware. Since AlmaLinux uses a significantly newer Linux kernel than CentOS 7, legacy kernel modules or device drivers may be incompatible. Therefore, a controlled pilot migration is essential to test hardware interactions, customized kernel modules, and specialized device drivers in a non-production environment to avoid surprises during the production cutover.

3. Security and Compliance Assessment

Security and compliance requirements are non-negotiable. Organizations must ascertain the need for specialized modules, such as FIPS-certified packages, for critical workloads. Additionally, companies must verify compliance with mandates like CIS/STIG, PCI-DSS, or ISO 27001. Current gaps in patch management or vulnerability scanning must be addressed by defining the new security hardening baseline and audit profiles for the AlmaLinux target environment before migration begins.

4. Application and Package Compatibility

Compatibility issues are a common source of migration failures. It is necessary to check if major applications, databases, and middleware are compatible with the AlmaLinux target version. This includes verifying library versions, runtime dependencies, and configuration files.

Pay special attention to major language runtime environments (e.g., Python, Java, PHP), as version changes can silently break legacy or in-house tools, requiring extensive pre-migration testing or code adjustments.

5. Internal Resource Allocation and External Support Strategy

Evaluate whether your internal team has the skills and capacity to handle potential migration challenges that come up. Unexpected issues like kernel panics, complex package conflicts, or OS-level bugs can quickly overwhelm internal resources.

Identifying where external support could help, such as specialized migration assistance, troubleshooting, compliance validation, or application configuration, can significantly reduce risk and accelerate migration timelines.

6. Risk Mitigation: Backup and Rollback Validation

At last, every robust migration plan requires a rigorously tested rollback strategy. Ensure that immutable backups of essential data, system configurations, and application snapshots are verified and up-to-date. Validate the procedures for restoring services quickly if unforeseen issues arise, and practice the entire rollback process in a staging environment. Being prepared for the worst-case scenario is the best way to guarantee minimal downtime and business continuity.

For a detailed step-by-step migration process, see our CentOS to AlmaLinux migration guide.

Common Pitfalls Enterprises Face During Migration

Enterprises often encounter issues that, if not addressed proactively, can cause costly downtime, data loss, or compliance gaps. Below are the most common pitfalls and the proactive strategies needed to avoid them:

1. Dependency Drift and Repository Management

Switching from CentOS repositories to AlmaLinux repositories can introduce unexpected package conflicts or missing dependencies. Some packages may be named differently, or have newer versions that are incompatible with your existing applications, leading to “dependency drift.”

Mitigation Tips:

• Test critical applications against the AlmaLinux repository in a staging environment.
• Lock package versions where necessary and maintain rigorous documentation of application dependencies.
• Consider using TuxCare-vetted repositories to ensure long-term package stability.

2. SELinux Policy and Security Differences

While AlmaLinux closely follows CentOS in functionality, subtle differences in SELinux enforcement or security contexts can cause immediate service disruptions. Applications that previously ran without issue may fail due to stricter or slightly altered policies inherited from the upstream RHEL version.

Mitigation Tips:

• Audit all active SELinux policies before migration.
• Test all critical services with SELinux enabled in the staging environment.
• Use tools like audit2allow to pre-emptively generate and test custom policies if standard policies are insufficient.

3. Application Regressions

Even minor differences in library versions, package builds, or system utilities can lead to unexpected application behavior. Legacy applications or proprietary software with complex dependencies are particularly vulnerable to these regressions.

Mitigation Tips:

• Maintain a detailed list of all critical applications and their deep-level dependencies.
• Validate each application in a controlled testing environment under realistic load.
• Standardize and verify the target version of language runtimes (e.g., Python, Java) across all migrated systems.

4. Kernel and Driver Compatibility Issues

Hardware drivers and custom kernel modules may not behave identically on the newer AlmaLinux kernel. This is especially relevant for specialized hardware like storage arrays, network cards, or older server models. Unexpected kernel panics or module failures can halt critical services.

Mitigation Tips:

• Verify compatibility with vendor documentation and the Hardware Compatibility List (HCL), particularly for complex storage configurations (LVM, RAID).
• Test all hardware interactions in a staging or lab environment.
• Work with vendor-provided drivers when possible, and have verified fallback drivers ready.

5. Breakage of Custom Scripts or Automation

Many enterprises rely heavily on in-house scripts for deployment, monitoring, backups, or maintenance. Scripts written for CentOS may fail due to path differences or package relocation in AlmaLinux.

Mitigation Tips:

• Audit all in-house shell and configuration management (e.g., Ansible, Puppet) scripts before migration.
• Test scripts in an AlmaLinux staging environment against the new paths and package names.
• Document modifications and version control all changes to automation code.

6. Skipping Load Testing and Production Mirroring

Skipping a proper testing phase is the most critical error. Enterprises often underestimate the cumulative failures that occur when multiple services interact under load in the new OS environment.

Mitigation Tips:

• Set up a dedicated staging environment that mirrors production in hardware specification and configuration.
• Conduct functional, security, load testing, and rollback validation.
• Validate all integration points between applications, databases, and third-party services.

7. Compliance and Security Oversights

Migration can inadvertently break compliance if regulatory requirements — such as security settings, audit logs, or cryptography modules — are not maintained or validated. Enterprises with obligations (e.g., healthcare, finance) risk audit failures or security breaches.

Mitigation Tips:

• Document all regulatory compliance requirements (e.g., PCI-DSS, HIPAA, SOC 2) before migration.
• Validate cryptography, logging, and audit settings in the staging environment.
• Leverage TuxCare Enterprise Support for FIPS continuity, CIS/STIG hardening, and compliance validation to ensure uninterrupted regulatory adherence.

Stability and Security: Post-Migration Strategy

Completing a migration from CentOS to AlmaLinux is only part of the journey. Enterprises need a structured post-migration strategy to ensure long-term stability, maintain security and compliance, and prevent operational disruptions. A clear plan reduces risk, improves system reliability, and sets the foundation for ongoing enterprise support.

1. Define Cyclical Patch Management and Testing Schedules

After migration, keeping AlmaLinux systems updated is critical for security. Enterprises must define clear, cyclical patch management workflows, including testing, deployment, and verified rollback procedures.

Key Actions:

• Monitor AlmaLinux release schedules and plan system updates accordingly.
• Test all critical updates in a staging environment before deployment to production.
• Ensure high-priority security patches are applied promptly to minimize vulnerability exposure.

2. Validate Monitoring, Logging, and Alerting

Migration can inadvertently disrupt existing monitoring, logging, and alerting configurations. Confirm that all metrics, logs, and alerts continue to function correctly and align with the new OS environment.

Key Actions:

• Validate log collection paths, formats, and retention policies, ensuring SIEM tools recognize new OS paths.
• Test alerting thresholds and notification systems against current operational requirements.
• Ensure monitoring tools integrate with AlmaLinux-specific metrics for comprehensive oversight.
• Verify and recalibrate performance baselines for CPU, memory, and disk I/O, as the new kernel/OS stack may have different characteristics.

3. Re-Run Security and Compliance Baselines

Post-migration, systems must immediately meet all regulatory and enterprise security standards. Compliance is not a one-time step but a continuous state.

Key Actions:

• Run comprehensive compliance scans to validate FIPS modules, CIS/STIG hardening profiles, and other security controls.
• Confirm that security configurations (e.g., firewall rules, user permissions) and automated audit logging remain intact and operational.
• Verify that the automated audit logging (e.g., auditd) and security reporting are fully functional.

4. Formalize Documentation for Audit and Operational Continuity

Clear, up-to-date documentation is critical for efficient troubleshooting, successful audits, and simplified future upgrades.

Key Actions:

• Record final system configurations, major package versions, and the history of applied patches.
• Document any custom scripts, unique application configurations, or deviations from standard AlmaLinux builds.
• Maintain strict version control for all infrastructure-as-code and automation scripts.

5. Define Support and Escalation Channels

Even with the best planning, unexpected issues can arise. Enterprises should establish clear internal and external support pathways for rapid resolution.

Key Actions:

• Identify internal teams responsible for initial break/fix, kernel issues, and application support.
• Define transparent escalation procedures and contact lists for high-severity issues.
• Use TuxCare Enterprise Support to cover critical services like kernel crash analysis, FIPS compliance maintenance, and complex application troubleshooting.

6. Iterative Optimization and Automation

Migration is an ideal opportunity to review and optimize IT operations for greater efficiency and security.

Key Actions:

• Review lessons learned from the migration process and update future migration playbooks.
• Evaluate patching, monitoring, and security processes for potential workflow improvements.
• Incorporate automation for routine tasks where possible, striving for a zero-downtime maintenance model, especially for security patching.

Addressing Enterprise Challenges with TuxCare

Migrating from CentOS to AlmaLinux is a complex project, especially for enterprises managing mission-critical workloads, strict compliance requirements, and diverse IT environments. TuxCare Enterprise Support helps organizations navigate these challenges with confidence, ensuring smooth migrations and long-term stability.

1. Vetted Repository and Reliable Updates

TuxCare maintains a vetted repository of all AlmaLinux and Rocky Linux updates with 16 years of support coverage. This guarantees patches are tested for compatibility and security, ensuring service continuity and predictability across all systems.

2. Extended Security Updates

TuxCare provides long-term security coverage for specific minor AlmaLinux and Rocky Linux versions, often extending the lifecycle beyond standard OS end-of-life dates.

• Continuous high and critical security updates for FIPS-certified releases.
• FIPS-compliant patches that preserve validated cryptography.
• Helps enterprises maintain compliance with CIS/STIG, PCI-DSS, ISO 27001, and other standards.

3. Expedited 24/7 Break-and-Fix Assistance

Migration-related issues often require rapid resolution. TuxCare provides round-the-clock, expert support for:

• Kernel crashes or OS-level issues requiring immediate attention.
• Package installation, update problems, and dependency conflicts.
• Hardware compatibility or specialized driver troubleshooting.
• Consultation on installation, configuration, or in-place migration tool usage.

Enterprises can also choose flexible support packages in 5, 10, or 20-hour bundles, giving them access to expert assistance without long-term commitments.

Ensuring a Smooth, Secure, and Compliant Migration with TuxCare

Migrating from CentOS to AlmaLinux is now a strategic necessity for organizations that need long-term stability, predictable updates, and strong security posture. While the transition requires planning, testing, and careful execution, a structured migration and post-migration strategy ensures you avoid downtime and compliance gaps.

With TuxCare Enterprise Support, organizations gain expert consultation and 24/7 break-fix support across installation, migration, package issues, OS bugs, and kernel troubleshooting — ensuring your AlmaLinux environment remains stable and secure. Consult TuxCare experts today to keep your operations running without disruption.

Summary

Article Name

Moving from CentOS to AlmaLinux or Rocky Linux

Description

Plan a smooth CentOS to AlmaLinux migration with this enterprise-ready checklist. Avoid common pitfalls and get expert support from TuxCare.

Author

Rohan Timalsina

Publisher Name

TuxCare

Publisher Logo