What this snippet does
An ARG declared before FROM is only usable in FROM lines unless it is redeclared inside the stage.
Why practise typing this
Typing env & arg code builds muscle memory for the symbols and indentation Docker uses most, which prose-based typing tests never cover. DevType measures your words per minute and accuracy on this snippet and tracks the individual characters you mistype, so later lessons can target them.
More Docker practice
- Setting an environment variableENV & ARG · beginner
- Multiple values in one layerENV & ARG · beginner
- Build-time argumentENV & ARG · intermediate
- ARG is gone at runtimeENV & ARG · intermediate
- Parameterised base imageENV & ARG · advanced
- Secrets leak through build argsENV & ARG · advanced