Post-Migration Checklist

After completing the migration from CentOS to AlmaLinux or Rocky Linux, follow this checklist item by item to verify that the system is functioning correctly.

Tip: Bookmark this page and go through each item after migration. Mark each check as complete in your own documentation as you go.

1. Verify the Operating System Version

First, confirm that the system has successfully switched to the target distribution.

Check os-release

$ cat /etc/os-release

Confirm that the NAME and ID fields show the correct distribution name (AlmaLinux or Rocky Linux).

Check redhat-release

$ cat /etc/redhat-release

Confirm the distribution identifier package

$ rpm -qa | grep -E '(almalinux|rocky)-release'

Confirm no leftover CentOS identifier packages

$ rpm -qa | grep centos-release

If CentOS packages still remain:

Clean up leftover CentOS packages

$ sudo dnf remove centos-release centos-logos centos-indexhtml 2>/dev/null
$ sudo dnf distro-sync -y

2. Verify the Kernel Version

Check the currently running kernel

$ uname -r

View all installed kernels

$ rpm -qa kernel-core | sort

Confirm the GRUB default kernel

$ sudo grubby --default-kernel

Ensure the running kernel is from the target distribution. If you are still using an old kernel:

Install the latest kernel and set it as default

$ sudo dnf install -y kernel
$ sudo grubby --set-default /boot/vmlinuz-$(rpm -q kernel-core --qf '%{VERSION}-%{RELEASE}.%{ARCH}\n' | sort -V | tail -1)

3. Check Running Services

List all failed services

$ systemctl list-units --type=service --state=failed

If any services have failed, investigate each one:

View details of a failed service

$ systemctl status <service-name>
$ journalctl -u <service-name> -n 50 --no-pager

Compare with the pre-migration service list

$ systemctl list-units --type=service --state=running > ~/services-after-migration.txt
$ diff ~/services-before-migration.txt ~/services-after-migration.txt

Check Key Services Individually

Check SSH service

$ systemctl is-active sshd

Check cron scheduler

$ systemctl is-active crond

Check system logging service

$ systemctl is-active rsyslog

Check firewall service

$ systemctl is-active firewalld

4. Verify Software Repositories

List all enabled repositories

$ dnf repolist --enabled

Confirm that the repositories point to the correct distribution. There should be no leftover CentOS repositories.

Check for leftover CentOS repository files

$ ls /etc/yum.repos.d/ | grep -i centos

Test repository availability

$ sudo dnf check-update

Confirm EPEL repository is working (if needed)

$ dnf repolist | grep epel

If EPEL is missing but needed:

Install EPEL

$ sudo dnf install -y epel-release

5. Test Applications

Web Services

Check Nginx status (if applicable)

$ systemctl is-active nginx && curl -s -o /dev/null -w "%{http_code}" http://localhost/

Check Apache/httpd status (if applicable)

$ systemctl is-active httpd && curl -s -o /dev/null -w "%{http_code}" http://localhost/

Databases

Check MySQL/MariaDB (if applicable)

$ systemctl is-active mariadb || systemctl is-active mysqld
$ mysqladmin ping 2>/dev/null && echo "Database connection OK"

Check PostgreSQL (if applicable)

$ systemctl is-active postgresql
$ sudo -u postgres psql -c "SELECT version();" 2>/dev/null

Programming Language Runtimes

Check PHP version (if applicable)

$ php -v 2>/dev/null

Check Python version

$ python3 --version

Check Java version (if applicable)

$ java -version 2>/dev/null

Custom Applications

For custom-built applications, perform the following checks:

Check if the application port is listening

$ sudo ss -tlnp | grep <application-port>

Test the application HTTP endpoint (if applicable)

$ curl -s http://localhost:<port>/health

6. SELinux Status

Check the current SELinux mode

$ getenforce

Under normal circumstances, this should return Enforcing. If it returns Disabled or Permissive, confirm whether this is the expected configuration.

View the SELinux configuration file

$ cat /etc/selinux/config

Check for SELinux denial records

$ sudo ausearch -m avc -ts recent 2>/dev/null | head -30

After migration, some files may have incorrect SELinux labels:

Relabel the filesystem (if SELinux issues exist)

$ sudo fixfiles -F onboot

This will relabel the entire filesystem on the next reboot. If you prefer not to reboot:

Relabel immediately (may take a long time)

$ sudo restorecon -Rv /etc /var /home

7. Firewall Rules

Check firewall status

$ sudo firewall-cmd --state

List all allowed services and ports

$ sudo firewall-cmd --list-all

Confirm critical ports are allowed

$ sudo firewall-cmd --query-port=22/tcp     # SSH
$ sudo firewall-cmd --query-port=80/tcp     # HTTP
$ sudo firewall-cmd --query-port=443/tcp    # HTTPS

Compare with the pre-migration firewall configuration:

List all zone configurations

$ sudo firewall-cmd --list-all-zones | grep -A 10 "active"

8. Network Configuration

Check network interface status

$ ip addr show

Check the default route

$ ip route show default

Check DNS configuration

$ cat /etc/resolv.conf

Test DNS resolution

$ dig +short google.com

Test internet connectivity

$ ping -c 3 8.8.8.8

Check NetworkManager connections

$ nmcli connection show

Confirm the hostname is correct

$ hostnamectl

9. Scheduled Tasks

Check root's crontab

$ sudo crontab -l

Check system-level cron jobs

$ ls -la /etc/cron.d/
$ ls -la /etc/cron.daily/
$ ls -la /etc/cron.weekly/

Check systemd timers

$ systemctl list-timers --all

10. Backup Verification

Confirm that the backup system is still working properly after migration.

Check if backup tools are available

$ which rsync && rsync --version | head -1

If using LVM snapshots, confirm snapshot status

$ sudo lvs

Important: After the migration is verified to be successful, it is recommended to immediately create a new full backup as a new baseline.

Create a post-migration package list snapshot

$ rpm -qa --queryformat '%{NAME}-%{VERSION}-%{RELEASE}.%{ARCH}\n' | sort > ~/packages-after-migration-verified.txt

11. System Updates

Confirm that the system can receive updates normally:

Check for available updates

$ sudo dnf check-update

Install all available updates

$ sudo dnf update -y

If the kernel was updated, reboot the system

$ sudo needs-restarting -r && echo "No reboot needed" || echo "Reboot required to apply kernel updates"

Quick Check Script

The following script performs most checks at once and outputs a report:

Run post-migration quick check

$ echo "===== System Version ====="
$ cat /etc/redhat-release
$ echo ""
$ echo "===== Kernel Version ====="
$ uname -r
$ echo ""
$ echo "===== SELinux Status ====="
$ getenforce
$ echo ""
$ echo "===== Failed Services ====="
$ systemctl list-units --type=service --state=failed --no-legend
$ echo ""
$ echo "===== Enabled Repositories ====="
$ dnf repolist --enabled 2>/dev/null
$ echo ""
$ echo "===== Firewall Status ====="
$ sudo firewall-cmd --state 2>/dev/null
$ echo ""
$ echo "===== Disk Usage ====="
$ df -h / /boot /var 2>/dev/null
$ echo ""
$ echo "===== Network Connectivity ====="
$ ping -c 1 -W 3 8.8.8.8 >/dev/null 2>&1 && echo "Internet reachable" || echo "Internet unreachable"
$ dig +short google.com >/dev/null 2>&1 && echo "DNS OK" || echo "DNS issue"
$ echo ""
$ echo "===== Leftover CentOS Packages ====="
$ rpm -qa | grep -i centos || echo "None found"

Next Steps

• Migrate to AlmaLinux — AlmaLinux migration steps
• Migrate to Rocky Linux — Rocky Linux migration steps
• Common Errors Quick Reference — Quick reference when encountering errors