flatcar · tormath1 · Aug 21, 2026 · Aug 11, 2026
@@ -22,7 +22,6 @@ Flatcar uses automated provisioning, read-only system images, and atomic updates
 | [Diagnostics and Fixing Issues](./diagnostics/) | Troubleshooting tools, logs, and rollback guidance. |
 | [Nebraska Update Manager & Releases](./updates-releases/) | Nebraska, release channels, and update management. |
 | [Security](./security/) | Hardening, authentication, encryption, and supply-chain topics. |
-| [CoreOS Migration](./coreos-migration/) | Migration guidance for CoreOS Container Linux users. |
 | [Developer Guides](./devguide/) | SDK and image-building documentation for developers. |
 | [How to Contribute](./contribute/) | Community and contribution information. |
 

@@ -121,10 +121,6 @@ The Dockerfile for the `ghcr.io/flatcar/google-cloud-flatcar-image-upload` image
 [bucket]: https://cloud.google.com/storage/docs/key-terms#bucket-names
 [google-cloud-flatcar-image-upload]: https://github.com/flatcar/flatcar-cloud-image-uploader/blob/master/google-cloud-flatcar-image-upload
 
-## Upgrade from CoreOS Container Linux
-
-You can also [upgrade from an existing CoreOS Container Linux system](../../coreos-migration/update-from-container-linux).
-
 ## Butane Config
 
 Flatcar Container Linux allows you to configure machine parameters, configure networking, launch systemd units on startup, and more via Butane Configs. These configs are then transpiled into Ignition configs and given to booting machines. Head over to the [docs to learn about the supported features][cl-configs].

@@ -297,7 +297,8 @@ update_engine_client -check_for_update
 
 ### Updating outdated versions
 
-Even if Flatcar tries to stay compatible with old versions, there are still some cases where it's not possible to update from an old release. The first common problem is that the SSL certificates might be so outdated that contacting the update server and downloading the update payload fails. The section on [updating from CoreOS Container Linux][update-from-container-linux] shows how to use HTTP together with `flatcar-update` to jump to a new Flatcar release. This resembles airgapped updates, which are also covered above.
+Even if Flatcar tries to stay compatible with old versions, there are still some cases where it's not possible to update from an old release. The first common problem is that the SSL certificates might be so outdated that contacting the update server and downloading the update payload fails. In that case, download the update payload over plain HTTP (instead of HTTPS) and apply it with `flatcar-update` as described in the airgapped update steps above.
+
 The second common problem is that old versions can't handle the new compressed btrfs `/usr` partition. A solution is to **first update to the LTS 2023** which are the releases with major version 3510. Afterwards one can switch to the Stable channel again. We hope to improve this in the future by letting the update server detect these situations.
 
 ### Management of config files
@@ -354,4 +355,3 @@ storage:
 [reboot-windows]: https://github.com/flatcar/locksmith#reboot-windows
 [systemd-env-vars]: ../../os-config/host-config/environment-variables/#system-wide-environment-variables
 [transpiler]: ../../fb-provision/butane/
-[update-from-container-linux]: ../../coreos-migration/update-from-container-linux
@@ -41,13 +41,7 @@ Check out our [release page](https://flatcar-linux.org/releases/) to see the lat
 
 ### How does Flatcar Container Linux differ from CoreOS Container Linux?
 
-The main difference is that Flatcar Container Linux is still maintained, while CoreOS Container Linux has been discontinued. Flatcar Container Linux is a drop-in replacement for CoreOS Container Linux. Any minor changes you may need to consider are documented in the [migration documentation](https://flatcar-linux.org/docs/latest/migrating-from-coreos/).
-
-### What are the plans for Flatcar Container Linux now that CoreOS has reached EOL?
-
-CoreOS Container Linux was [discontinued in 2020](https://coreos.com/os/eol/#timeline). Flatcar Container Linux understands itself as the successor in spirit and will continue following the philosophy pioneered by CoreOS, delivering a fully open source, minimal-footprint, secure by default and always up-to-date Linux distribution for running containers at scale.
-
-We will continue to actively develop and support Flatcar Container Linux; updating key components such as the Linux kernel, systemd and Docker. We will also maintain support for Flatcar Container Linux as a drop-in replacement for CoreOS Container Linux for an extended migration period.
+The main difference is that Flatcar Container Linux is still maintained, while CoreOS Container Linux has been discontinued. Flatcar Container Linux is a drop-in replacement for CoreOS Container Linux.
 
 ### What is the significance of the Flatcar Container Linux name?