# "Choosing a Runtime Base on Zerops"


## Keywords
alpine, ubuntu, docker, container, base image, linux, runtime base, os, choose base, which container

## TL;DR
**Use Alpine** as the default base for all services. Use Ubuntu only when you need system packages not available in Alpine. Use Docker only for pre-built images.

## Decision Matrix

| Need | Choice | Why |
|------|--------|-----|
| **Any standard app** | **Alpine** (default) | ~5MB, fast, secure, sufficient for 95% of apps |
| System packages (apt) | Ubuntu | Full Debian ecosystem, ~100MB |
| Pre-built Docker images | Docker | VM-based, bring your own image |
| CGO / native libs | Ubuntu | Better glibc compatibility than Alpine's musl |

## Alpine (Default)

- Size: ~5MB base
- Package manager: `apk add`
- Best for: All runtimes (Node.js, Python, Go, Rust, Java, PHP, etc.)
- Zerops uses Alpine as default base for all managed runtimes

## Ubuntu

- Size: ~100MB base
- Package manager: `apt-get install`
- Version: 24.04 LTS
- Use when: You need packages not available in Alpine, or need glibc (not musl)
- Example: Go apps with CGO, Python packages with C extensions that don't compile on musl

## Docker

- **Runs in a VM** (not a container) — slower boot, higher overhead
- Network: **Must use `--network=host`** or `network_mode: host` in compose
- Scaling: Fixed resources only (no min-max auto-scaling), VM restarts on resource change
- Disk: Can only increase, never decrease without recreation
- Build phase runs in containers (not VMs)
- **Always use specific version tags** — `:latest` is cached and won't re-pull

## Gotchas
1. **Alpine uses musl**: Some C libraries may not compile — use Ubuntu if you hit musl issues
2. **Docker is VM-based**: Vertical scaling restarts the VM — expect brief downtime
3. **Docker `:latest` is cached**: Zerops won't re-pull — always use specific tags like `myapp:1.2.3`
4. **Docker requires host networking**: Without `--network=host`, the container can't receive traffic

## See Also
- `zerops://runtimes/{name}` — per-runtime guides (e.g. zerops://runtimes/alpine, zerops://runtimes/docker)
- zerops://themes/core — build environment rules