Installation: Add Release-Via-Docker option

docs/installation/otp_en.md

@@ -13,6 +13,9 @@ You will be running commands as root. If you aren't root already, please elevate
 
 Similarly to other binaries, OTP releases tend to be only compatible with the distro they are built on, as such this guide focuses only on Debian/Ubuntu and Alpine.
 
+!!! note
+    If you get `GLIBC_... not found` errors on Debian/Ubuntu, you can run the OTP release from `/opt/pleroma` inside a newer distro container without upgrading the host. See [`release_to_docker_en.md`](release_to_docker_en.md).
+
 ### Detecting flavour
 
 Paste the following into the shell:

docs/installation/release_to_docker_en.md

@@ -0,0 +1,61 @@
+# Running OTP releases via Docker (glibc shim)
+
+Pleroma OTP releases are built on specific distros. If your host OS is older than
+the build environment, you may hit runtime linker errors such as:
+
+```
+/lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.38' not found
+```
+
+If you don't want to upgrade your host OS, you can run the existing OTP release
+from `/opt/pleroma` inside an Ubuntu 24.04 container while keeping your existing
+host config and data directories.
+
+This approach uses a small "shim" container image to provide a newer `glibc`.
+It is **not** the official Pleroma Docker image.
+
+## Requirements
+
+- Docker Engine + the Docker Compose plugin on the host
+- Root access (or equivalent access to the Docker socket)
+- Existing OTP release in `/opt/pleroma`
+- Existing config in `/etc/pleroma` and data in `/var/lib/pleroma`
+
+## Setup
+
+1. Copy the provided templates:
+
+   ```sh
+   mkdir -p /etc/pleroma/container
+   cp -a /opt/pleroma/installation/release-to-docker/* /etc/pleroma/container/
+   ```
+
+2. Build the shim image:
+
+   ```sh
+   cd /etc/pleroma/container
+   docker compose build
+   ```
+
+3. Replace your systemd unit:
+
+   ```sh
+   cp /etc/pleroma/container/pleroma.service /etc/systemd/system/pleroma.service
+   systemctl daemon-reload
+   systemctl enable --now pleroma
+   journalctl -u pleroma -f
+   ```
+
+## Running migrations / `pleroma_ctl`
+
+Migrations are run automatically by default when the container starts. You can
+disable this by setting `PLEROMA_RUN_MIGRATIONS=0` in
+`/etc/pleroma/container/docker-compose.yml`.
+
+To run admin commands inside the container:
+
+```sh
+cd /etc/pleroma/container
+docker compose exec pleroma /opt/pleroma/bin/pleroma_ctl status
+docker compose run --rm --no-deps pleroma /opt/pleroma/bin/pleroma_ctl migrate
+```