CentOS operating system lifecycle and solutions after end of life (EOL) - Elastic Compute Service

The CentOS operating system has reached its end-of-life (EOL). Using an EOL system exposes it to security vulnerabilities, makes it a target for attacks, and can lead to non-compliance with security regulations. Assess the risks to your Elastic Compute Service (ECS) instances and take action to ensure your services remain stable and secure.

Impacts of CentOS EOL

As of June 30, 2024, the CentOS operating system has reached its EOL. Continued use presents a security risk. Existing ECS instances can continue to run, but they will no longer receive software maintenance or support, such as bug fixes and feature updates.

Version	Release date	EOL date	Recommended action
CentOS 8	2019-09-24	2021-12-31	Migrate immediately
CentOS 7	2014-07-07	2024-06-30	Migrate immediately
CentOS 6	2011-11-27	2020-11-30	Migrate immediately
CentOS 5	2007-04-12	2017-03-31	Migrate immediately

Recommendations after CentOS EOL

You must address the operating system EOL based on your business requirements. For services that are exposed to the public internet or that require high system stability and security, you must assess the EOL risks and promptly develop a response plan.

For new services: Use a CentOS-compatible operating system that is in its mainstream support phase to ensure long-term support and security. Do not use CentOS images that have already reached EOL to create new ECS instances.
For existing services: Immediately prepare to replace the operating system or perform an operating system migration.

Replace or upgrade the operating system

Step 1: Choose a target operating system

Before you migrate or replace your operating system, select a Linux operating system to replace CentOS based on factors such as security compliance, stability, operating system compatibility, budget, and long-term strategy.

Step 2: Preparations

Before you perform any migration or replacement, complete these preparations:

Application testing: Create a test environment with the target operating system, deploy your applications, and perform comprehensive functional, performance, and compatibility testing. Ensure that all business logic works correctly in the new environment.
Migration test: Rehearse your chosen migration solution in a non-production environment to familiarize yourself with the process and potential issues. Refer to Troubleshooting Linux operating system migration issues.
Plan a migration window: During the migration process, the system kernel and software packages of the original instance will be updated, and the instance will be restarted multiple times. Your services will be unavailable during this period. Assess the impact and plan a suitable migration window to avoid business disruptions.

Step 3: Perform the operating system migration

Important

Before migration, you must create snapshots for the system disk and all data disks of your instance to prevent data loss. If a snapshot is being created while you start the migration, the migration will fail. Wait for the snapshot creation to complete before starting the migration.

Solution	Use cases	Impacts	Procedure
In-place migration	Your business environment is complex and difficult to rebuild. You need to retain all data and configurations on the system disk.	Data on the system disk is retained. The ECS instance restarts during the migration and is unavailable.	In-place migration is applicable only to operating systems that are binary-compatible with CentOS: To migrate from CentOS 7/8 to Alibaba Cloud Linux/Anolis OS/Red Hat Enterprise Linux, see Operating system migration to complete the migration in the ECS console. To migrate from CentOS 7 to AlmaLinux, see ELevating CentOS 7 to AlmaLinux and log on to the ECS instance to perform the migration. To migrate from CentOS 7/8 to Rocky Linux 8/9, see How to migrate to Rocky Linux from CentOS and log on to the ECS instance to perform the migration.
Replace the system disk	You want to retain the original instance configuration (such as IP address and instance ID), and the application can be redeployed.	The system disk is released and its data cannot be recovered. During the replacement, the ECS instance restarts and is unavailable.	After replacing the operating system (system disk), redeploy your applications and services. Verify that they are functioning correctly, then switch the production traffic. Before switching, be sure to back up your data and collect relevant information from the original instance.
Redeploy the environment	Your business cannot tolerate downtime and requires a smooth traffic switch.	You must migrate data and traffic yourself and bear the cost of the new ECS instance.	You can replace the original instance by creating a custom instance. After you purchase the new instance, redeploy your applications and services. After you verify your services, switch the business traffic to the new instance and stop the original instance.

FAQ

Which operating systems can I migrate CentOS to?

Operating systems that are binary-compatible with CentOS

A binary-compatible OS lets you run your existing applications and software immediately after migration, without recompiling them. Migrating to a CentOS-compatible operating system does not guarantee bug compatibility. Please consult the community support documentation for the target operating system to resolve such issues.

Operating system	Description	Billing	Technical support
Alibaba Cloud Linux	Provided by Alibaba Cloud and fully compatible with RHEL/CentOS. This operating system is highly optimized for Alibaba Cloud and includes free long-term support and maintenance.	No	Alibaba Cloud support
Anolis OS	Provided by the OpenAnolis community, it is 100% compatible with the CentOS 8 software ecosystem and also compatible with other mainstream Linux distributions. It is a fully open-source, neutral, and open distribution with enterprise-grade performance, stability, security, and reliability.	No	Alibaba Cloud support
Red Hat Enterprise Linux	An enterprise operating system provided by Red Hat. It requires a paid subscription to use and access Red Hat's services.	Involves operating system license fees for the image. See Red Hat.	Joint support from Alibaba Cloud and Red Hat
CentOS Stream	CentOS Stream is a rolling-release distribution provided by the official CentOS project.	No	Community support
Rocky Linux	A community-driven, enterprise-grade operating system that is compatible with RHEL and serves as a replacement for CentOS.	No	Community support
AlmaLinux	A community fork of CentOS built by the CloudLinux team. It is 1:1 binary compatible with RHEL and supports replacing the operating system without downtime.	No	Community support

Other operating systems

Operating system	Description	Billing	Technical support
SUSE Linux Enterprise Server	An operating system from SUSE that adapts to any environment and is optimized for performance, security, and reliability.	Involves operating system license fees for the image. See Image billing.	Joint support from Alibaba Cloud and SUSE
Ubuntu	A Linux distribution developed by Canonical. You can install a graphical desktop on Ubuntu for ease of use.	No	Community support
Debian	Debian is a popular Linux operating system known for its stability, security, and free software principles.	No	Community support
OpenSUSE	An operating system based on the Linux kernel, developed and maintained by the OpenSUSE project community with sponsorship from companies like SUSE.	No	Community support

How do I convert CentOS 7 to Red Hat Enterprise Linux (RHEL) 7?

The following steps require you to log in to the instance and manually execute commands to convert CentOS 7 to RHEL 7. To automate these manual steps, use the operating system migration to convert CentOS 7 to RHEL 7.

Important

Before the conversion, stop important applications, database services, and data storage services to prevent data loss from errors. You must also create snapshots to back up important data.

(Conditional) If your server is an Alibaba Cloud server with Security Center installed, you must first uninstall the Security Center client.
Security Center is the default security enhancement tool for CentOS, while RHEL 7 uses security tools provided by Red Hat. Incompatibilities and conflicts may exist between Security Center and the tools in RHEL 7.

Download the new Alibaba Cloud repository files.

sudo wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo
sudo wget -O /etc/yum.repos.d/epel.repo https://mirrors.aliyun.com/repo/epel-7.repo

Update the system packages and restart the system.
```
sudo yum -y update
sudo reboot
```

Download and install the convert2rhel tool from the official Red Hat website.

sudo curl -o /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release https://security.access.redhat.com/data/fd431d51.txt
sudo curl -o /etc/yum.repos.d/convert2rhel.repo https://cdn-public.redhat.com/content/public/repofiles/convert2rhel-for-rhel-7-x86_64.repo
sudo yum -y install convert2rhel

Purchase a software license for the ECS instance on Alibaba Cloud.
To download RHEL software, you must purchase and activate a Red Hat Enterprise Linux license.

Convert CentOS 7 to RHEL 7.

sudo convert2rhel -y  --no-rhsm --enablerepo rhui-rhel-7-server-rhui-rpms --enablerepo rhui-rhel-7-server-rhui-extras-rpms --enablerepo rhui-rhel-7-server-rhui-optional-rpms

The process will take some time. A message similar to the following appears when the conversion is complete.

Restart the system.
After the conversion is complete, you will be prompted to restart the system. Restarting allows the system to boot with the new RHEL kernel. Then, run cat /etc/redhat-release to check if the operating system was successfully converted.
```
sudo reboot
```
Calibrate the operating system of the instance.
After the conversion, the Operating System displayed on the ECS instance details page (which depends on the OS property of the image used to create the instance) will differ from the actual operating system (Red Hat Enterprise Linux Server release 7.9). To update the instance's operating system platform information, calibrate the operating system of the instance.

How do I switch repository addresses for CentOS 6 after EOL?

The content at the CentOS 6 repository address http://mirror.centos.org/centos-6/ has been removed. Third-party mirror sites have also removed their CentOS 6 repositories. Alibaba Cloud's repositories at http://mirrors.cloud.aliyuncs.com and http://mirrors.aliyun.com can no longer synchronize with the CentOS 6 repository. Continuing to use the default CentOS 6 repository configuration on Alibaba Cloud will result in an error. An example of the error is shown below: centos 6 error

Solution

Important

This topic primarily describes operations and configurations for ECS instances. If your server is not an ECS instance, you must ensure it has public network access, and you must replace http://mirrors.cloud.aliyuncs.com with http://mirrors.aliyun.com. For example, switch the YUM repository to http://mirrors.aliyun.com/centos-vault/6.10/ and the EPEL repository to http://mirrors.aliyun.com/epel-archive/6/.

Log on to the ECS instance.
1. Go to the ECS console - Instances page. In the top-left corner, select the resource group and region where your target resource is located.
2. Navigate to the details page of the target instance, click Connect, and select Workbench. Follow the prompts to log in and access the terminal.

Switch the YUM repository.

sudo vim /etc/yum.repos.d/CentOS-Base.repo

Press i to enter edit mode and change the content to the following.

[base]
name=CentOS-6.10
enabled=1
failovermethod=priority
baseurl=http://mirrors.cloud.aliyuncs.com/centos-vault/6.10/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.cloud.aliyuncs.com/centos-vault/RPM-GPG-KEY-CentOS-6

[updates]
name=CentOS-6.10
enabled=1
failovermethod=priority
baseurl=http://mirrors.cloud.aliyuncs.com/centos-vault/6.10/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.cloud.aliyuncs.com/centos-vault/RPM-GPG-KEY-CentOS-6

[extras]
name=CentOS-6.10
enabled=1
failovermethod=priority
baseurl=http://mirrors.cloud.aliyuncs.com/centos-vault/6.10/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.cloud.aliyuncs.com/centos-vault/RPM-GPG-KEY-CentOS-6

After editing, press the Esc key, enter :wq, and press Enter to save and exit the file.

Switch the EPEL repository.

sudo vim /etc/yum.repos.d/epel.repo

Press i to enter edit mode and change the content to the following to switch the repository.

[epel]
name=Extra Packages for Enterprise Linux 6 - $basearch
enabled=1
failovermethod=priority
baseurl=http://mirrors.cloud.aliyuncs.com/epel-archive/6/$basearch
gpgcheck=0
gpgkey=http://mirrors.cloud.aliyuncs.com/epel-archive/RPM-GPG-KEY-EPEL-6

After editing, press the Esc key, enter :wq, and press Enter to save and exit the file.

Run the yum repolist command. If the repository list is displayed successfully without a 404 error, the switch was successful.

How do I keep repository settings when creating custom images on CentOS 6?

When you use a custom image to create a new ECS instance, cloud-init automatically initializes the system's repository configuration upon startup. If you want to create a custom image from an instance with a custom repository configuration and preserve it, you must modify the cloud-init configuration file /etc/cloud/cloud.cfg on the instance before creating the custom image.

Edit the /etc/cloud/cloud.cfg file.
```
sudo vim /etc/cloud/cloud.cfg
```
Press i to enter edit mode and use # to comment out the - source-address module under cloud_init_modules:.
After commenting, the configuration information in the file should look like this:
After editing, press the Esc key, enter :wq, and press Enter to save and exit the file.

References

For an overview of the operating system lifecycle, including the details of each stage and standard solutions for EOL, see Operating system lifecycle overview.