How to Migrate from CentOS to AlmaLinux: Complete Step-by-Step Guide (2026)

CentOS as we knew it is dead. Red Hat ended CentOS Linux 8 on December 31, 2021, and CentOS 7 reached end-of-life on June 30, 2024. If you’re still running CentOS, your servers are no longer receiving security patches — and that’s a ticking time bomb.

AlmaLinux is the most popular CentOS replacement. It’s 1:1 binary-compatible with RHEL, backed by CloudLinux, and provides 10 years of free support. This guide walks you through the entire migration process, from pre-flight checks to post-migration verification.

Migration Paths Overview

Phase 1: Pre-Migration Checklist

1.1 Create a Full Backup

# Full system backup
tar czf /backup/full-system-$(date +%Y%m%d).tar.gz \
  --exclude=/proc --exclude=/sys --exclude=/dev \
  --exclude=/run --exclude=/tmp --exclude=/backup /

# Database backups
mysqldump --all-databases > /backup/mysql-all-$(date +%Y%m%d).sql
pg_dumpall > /backup/postgres-all-$(date +%Y%m%d).sql

# List all installed packages (for reference)
rpm -qa --qf "%{NAME}\n" | sort > /backup/installed-packages.txt

# Save current configs
cp -r /etc /backup/etc-backup-$(date +%Y%m%d)

1.2 Check Current System Status

# Check OS version
cat /etc/os-release

# Check kernel
uname -r

# Check disk space (need at least 5GB free)
df -h /

# Check for third-party repos
yum repolist all

# Check for custom kernel modules
lsmod | grep -v "^Module"

# Check SELinux status
getenforce

# Check running services
systemctl list-units --type=service --state=running

1.3 Document Your Environment

Before migrating, document everything:

• All running services and their configurations
• Custom firewall rules (firewall-cmd --list-all)
• Cron jobs (crontab -l for all users)
• Third-party repositories
• Custom kernel parameters (/etc/sysctl.conf)
• SSL certificates and their expiration dates
• Network configuration (static IPs, bonds, VLANs)

Phase 2: CentOS 8 → AlmaLinux 8 (In-Place Migration)

This is the easiest migration path. The almalinux-deploy script handles everything automatically.

Step 1: Download and Run the Migration Script

# Download the official migration script
curl -O https://raw.githubusercontent.com/AlmaLinux/almalinux-deploy/master/almalinux-deploy.sh

# Make it executable
chmod +x almalinux-deploy.sh

# Run the migration (as root)
sudo bash almalinux-deploy.sh

What the Script Does:

1. Checks system compatibility and disk space
2. Removes CentOS-specific packages and GPG keys
3. Replaces CentOS repositories with AlmaLinux repositories
4. Installs AlmaLinux release packages
5. Runs dnf distro-sync to synchronize all packages
6. Updates GRUB configuration with AlmaLinux branding

Step 2: Reboot and Verify

# Reboot the server
sudo reboot

# After reboot, verify the migration
cat /etc/os-release
# Should show: AlmaLinux 8.x

# Check all packages are from AlmaLinux
rpm -qa --qf "%{NAME} %{VENDOR}\n" | grep -v "AlmaLinux" | grep -v "Red Hat"

# Verify kernel
uname -r

# Check services are running
systemctl --failed

Phase 3: AlmaLinux 8 → AlmaLinux 9 (Major Upgrade)

After migrating to AlmaLinux 8, you should upgrade to AlmaLinux 9 for the latest features and longest support (until 2032). AlmaLinux provides the ELevate tool based on Red Hat’s leapp framework.

Step 1: Prepare the System

# Update AlmaLinux 8 fully
sudo dnf update -y
sudo reboot

# Install ELevate packages
sudo dnf install -y http://repo.almalinux.org/elevate/elevate-release-latest-el8.noarch.rpm

# Install the leapp upgrade tool
sudo dnf install -y leapp-upgrade leapp-data-almalinux

Step 2: Run Pre-Upgrade Check

# Run the pre-upgrade assessment
sudo leapp preupgrade

# Review the report
cat /var/log/leapp/leapp-report.txt

# Common inhibitors and fixes:
# 1. Remove pam_pkcs11 module if detected
sudo leapp answer --section remove_pam_pkcs11_module_check.confirm=True

# 2. Remove make-devel if present
sudo dnf remove make-devel -y

# 3. Fix network interface naming
# Check if using old-style names (eth0)
# If so, AlmaLinux 9 uses predictable names (ens33, enp0s3)

Step 3: Run the Upgrade

# Start the upgrade process
sudo leapp upgrade

# This will:
# - Download AlmaLinux 9 packages
# - Create an upgrade initramfs
# - Schedule the upgrade for next boot

# Reboot to perform the upgrade
sudo reboot

# The system will boot into an upgrade environment
# This takes 15-45 minutes depending on packages installed
# DO NOT interrupt this process

Step 4: Post-Upgrade Verification

# Verify AlmaLinux 9
cat /etc/os-release
# NAME="AlmaLinux"
# VERSION="9.x"

# Check kernel version
uname -r
# Should be 5.14.x or newer

# Rebuild the RPM database
sudo rpm --rebuilddb

# Clean up old packages
sudo dnf clean all

# Check for any remaining EL8 packages
rpm -qa | grep el8

# Remove leftover upgrade artifacts
sudo rm -rf /root/tmp_leapp_py3
sudo dnf remove leapp-upgrade-el8toel9 leapp-data-almalinux -y

# Verify all services
systemctl --failed
systemctl list-units --type=service --state=running

Phase 4: CentOS 7 Migration (Special Considerations)

Option A: ELevate Two-Step Upgrade (In-Place)

# Step 1: CentOS 7 -> AlmaLinux 8
sudo yum install -y http://repo.almalinux.org/elevate/elevate-release-latest-el7.noarch.rpm
sudo yum install -y leapp-upgrade leapp-data-almalinux
sudo leapp preupgrade
# Fix all inhibitors from the report
sudo leapp upgrade
sudo reboot
# Wait for upgrade to complete

# Step 2: AlmaLinux 8 -> AlmaLinux 9
# Follow Phase 3 above

Option B: Fresh Install + Data Migration (Recommended for CentOS 7)

For CentOS 7 servers, we strongly recommend a fresh AlmaLinux 9 install with data migration. Here’s why:

• CentOS 7 uses Python 2.7, old OpenSSL, and outdated libraries
• Two major version jumps (7→8→9) compound risks
• Fresh install gives you a clean, optimized system
• Takes about the same time as two-step ELevate

# On the OLD CentOS 7 server: Export data
# -----------------------------------------
# Databases
mysqldump --all-databases --single-transaction > /backup/mysql-all.sql
pg_dumpall > /backup/postgres-all.sql

# Web content
tar czf /backup/www.tar.gz /var/www/

# Configs
tar czf /backup/configs.tar.gz /etc/nginx/ /etc/httpd/ /etc/php* /etc/my.cnf* \
  /etc/postfix/ /etc/ssl/ /etc/letsencrypt/

# Cron jobs
for user in $(cut -f1 -d: /etc/passwd); do
  crontab -l -u $user 2>/dev/null > /backup/cron-$user.txt
done

# User accounts (if needed)
cp /etc/passwd /etc/shadow /etc/group /backup/

# On the NEW AlmaLinux 9 server: Import data
# -------------------------------------------
# Install fresh AlmaLinux 9 (minimal or server)
# Install required services (nginx, php, mysql, etc.)
# Restore databases, web content, configs
# Update config file paths if changed between versions
# Test everything before switching DNS

Post-Migration Checklist

Common Pitfalls & Solutions

1. Third-Party Repositories Breaking

dnf install epel-release
dnf install https://rpms.remirepo.net/enterprise/remi-release-9.rpm

2. PHP Version Changes

3. MySQL/MariaDB Version Jump

4. Network Interface Naming

5. SELinux Denials After Upgrade

sudo touch /.autorelabel
sudo reboot

Why AlmaLinux Over Rocky Linux?

Both AlmaLinux and Rocky Linux are excellent CentOS replacements. Here’s why many choose AlmaLinux:

• CloudLinux backing — 20+ years of enterprise Linux experience, especially in hosting
• ELevate project — Official migration tooling from CentOS/RHEL (Rocky doesn’t offer this)
• cPanel/WHM support — Officially supported by cPanel
• FIPS 140-3 certification — In progress, critical for government/regulated industries
• Larger community — More contributors, faster releases, broader testing
• Foundation-governed — AlmaLinux OS Foundation ensures community ownership

Further Reading on Dargslan

• AlmaLinux vs Ubuntu Server in 2026: Which Linux Distro Should You Run?
• Mastering Midnight Commander on AlmaLinux
• Linux Server Hardening: The Complete Security Checklist
• How to Set Up a Production-Ready Linux Web Server
• RHCSA vs LFCS vs LPIC: Which Linux Certification?

Final Verdict