Build an Image with an Explicit Tag

The Situation

Docker automation with Bash

Task

Build the Dockerfile in a supplied directory and inspect the resulting image.

Save as build-image.sh. This script uses Bash.

#!/usr/bin/env bash
set -euo pipefail

if [[ $# -ne 2 ]]; then
    printf 'Usage: bash build-image.sh CONTEXT IMAGE:TAG\n' >&2
    exit 2
fi

context_dir=$1
image_ref=$2

if [[ ! -f "$context_dir/Dockerfile" ]]; then
    printf 'Dockerfile not found in the supplied context.\n' >&2
    exit 2
fi

if [[ "$image_ref" == -* || "$image_ref" != *:* || "$image_ref" == *: ]]; then
    printf 'Supply an image name with an explicit nonempty tag.\n' >&2
    exit 2
fi

docker build --tag "$image_ref" -- "$context_dir"
docker image inspect --format '{{.Id}}' "$image_ref"

Run

From the custom-image lab directory:

bash build-image.sh . docker-lab-site:3

Docker performs full validation of the reference. The script’s check is a basic guard against accidentally omitting a tag.

Verify

A missing Dockerfile should return a nonzero exit status. A successful build should print the image ID.

Production Extension

Use a CI commit identifier as the tag, test the image, and record its registry digest after publication. Keep registry credentials in the CI secret store.

Docker Roadmap

Build an Image with an Explicit Tag

Task

Run

Verify

Production Extension

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