Architecture

How daemonless container images are layered.

Image Layers

flowchart LR
    base_core["base-core<br/><small>4 images</small>"]
    base_exec["base-exec<br/><small>72 images</small>"]
    base_rcd["base-rcd<br/><small>16 images</small>"]
    base["base<br/><small>4 images</small>"]
    arr_base["arr-base<br/><small>4 images</small>"]
    nginx_base["nginx-base<br/><small>9 images</small>"]
    nginx["nginx<br/><small>18 images</small>"]
    postgres["postgres<br/><small>2 images</small>"]
    node["node"]
    python["python"]
    base_core --> base_exec
    base_core --> base_rcd
    base_core --> base
    base_exec --> arr_base
    base_rcd --> nginx_base
    base_exec --> nginx
    base_exec --> postgres
    base_core --> node
    base_core --> python
    classDef baseStyle fill:#ab2b28,stroke:#333,color:#fff
    classDef intermediateStyle fill:#d35400,stroke:#333,color:#fff
    class base_core,base_exec,base_rcd,base baseStyle
    class arr_base,nginx_base,nginx,postgres,node,python intermediateStyle

Base Layer

base-exec is the default. The app is the container's command (CMD), so its exit is the container's exit, and the runtime does the restarting, stopping, health checks and logs. Appliances that bundle several services (an app behind nginx, an app with its own database) use base-rcd, where rcd starts the services in order and restarts any that crash.

Both run the same setup before the app starts: PUID/PGID remap the bsd user, then the scripts in /daemonless/init.d and your own in /daemonless/custom.d. See Development for how an image is put together.

Intermediate Layers

Build Order

When an image changes, the images built on it are rebuilt:

1. base-core changes: rebuild everything
2. base-exec or base-rcd changes: rebuild the images on it
3. An intermediate image changes: rebuild its children only

Images by Parent

Each parent is indented under the image it is built on.