# Compose Rewrite

This page explains how PodRun generates `docker-compose.podrun.yml` on the remote host so the same compose file runs on remote Podman without edits.

## Why a Copy

A local `docker-compose.yml` usually binds host ports (`8080:80`), which collide on a shared remote host, and relative-path volumes need the `:z` label on SELinux hosts. PodRun rewrites only the remote copy and leaves the local file untouched.

## Steps

| Step | Action |
|---|---|
| 1 | Look for `docker-compose.yml`, then `docker-compose.yaml` on the remote host; return an error if neither exists |
| 2 | Copy it to `docker-compose.podrun.yml` |
| 3 | Strip host ports with three `sed` rules |
| 4 | Append `:z` to volumes starting with `./` using `awk` |

## Port Stripping Rules

| Original | Rewritten |
|---|---|
| `"8080:80"` | `"80"` |
| `${WEB_PORT}:80` | `80` |
| `${WEB_PORT:?error}:80` | `80` |

With host ports removed, Podman assigns random host ports to container ports; the `podman ps` table printed at the end of `up -d` shows the actual mappings.

## Volume Rules

| Original | Rewritten |
|---|---|
| `- ./data:/data` | `- ./data:/data:z` |
| `- ./data:/data:ro` | Intended `- ./data:/data:ro,z`; the implementation uses `gsub` with a `\1` backreference, which POSIX awk `gsub` does not support, so the actual output is unverified |
| `- ./data:/data:ro,z` | Unchanged |

Only relative volumes starting with `./` are touched; named volumes and absolute paths stay as-is. The rules use `\s`, so the remote awk must support it (for example gawk); the macOS system awk does not, and the rules never match there.

## Execution

`up` first clears old containers with `podman compose -f docker-compose.podrun.yml down -v`, then runs your command, such as `up -d`, with the same file. `clear` also uses this copy.

Passthrough commands (`down`, `ps`, `logs`, and others) currently run `podman compose <args>` in the remote folder without `-f docker-compose.podrun.yml`.