What this snippet does
A cached update layer can pair with stale package indexes, so update and install belong in one RUN.
Expected output
E: Unable to locate package nginx
Why practise typing this
Typing dockerfile basics 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.
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