How to set image name in Dockerfile? - docker

Question

You can set image name when building a custom image, like this:
docker build -t dude/man:v2 . # Will be named dude/man:v2
Is there a way to define the name of the image in Dockerfile, so I don't have to mention it in the docker build command?

Answer 1

Using -t on invocation
How to build an image with custom name without using yml file:
docker build -t image_name .
How to run a container with custom name:
docker run -d --name container_name image_name

Answer 2

Workaround using docker-compose
Tagging of the image isn't supported inside the Dockerfile. This needs to be done in your build command. As a workaround, you can do the build with a docker-compose.yml that identifies the target image name and then run a docker-compose build. A sample docker-compose.yml would look like
version: '2'
services:
man:
build: .
image: dude/man:v2
That said, there's a push against doing the build with compose since that doesn't work with swarm mode deploys. So you're back to running the command as you've given in your question:
docker build -t dude/man:v2 .
Personally, I tend to build with a small shell script in my folder (build.sh) which passes any args and includes the name of the image there to save typing. And for production, the build is handled by a ci/cd server that has the image name inside the pipeline script.

Answer 3

Workaround using docker-compose
Here is another version if you have to reference a specific docker file:
version: "3"
services:
nginx:
container_name: nginx
build:
context: ../..
dockerfile: ./docker/nginx/Dockerfile
image: my_nginx:latest
Then you just run
docker-compose build

Answer 4

My Dockerfile alone solution is adding a shebang line:
#!/usr/bin/env -S docker build . --tag=dude/man:v2 --network=host --file
FROM ubuntu:22.04
# ...
Then chmod +x Dockerfile and ./Dockerfile is to go.
I even add more docker build command line arguments like specifying a host network.
NOTE: env with -S/--split-string support is only available for newer coreutils versions.

Answer 5

With a specific Dockerfile you could try:
docker build --tag <Docker Image name> --file <specific Dockerfile> .
for example
docker build --tag second --file Dockerfile_Second .

Answer 6

Workaround using Docker (and a Makefile)
Generally in Docker you can't say what you want the image to be tagged as in the Dockerfile. So what you do is
Create a Dockerfile
Create a Makefile
.PHONY: all
all: docker build -t image_name .
Use make instead of invoking docker build directly
Or, use buildah
But here is a better idea... Don't build images with Docker! Instead build them with buildah, the new build tool provided by the podman crew which uses shell (or any language), allows building in the cloud easily (without using a different project like kaniko), and allows rootless building of images! At the end of the build script just save the image inside with buildah commit. Here is what it looks like.
#!/bin/sh
# Create a new offline container from the `alpine:3` image, return the id.
ctr=$(buildah from "alpine:3")
# Create a new mount, return the path on the host.
mnt=$(buildah mount "$ctr")
# Copy files to the mount
cp -Rv files/* "$mnt/"
# Do some things or whatever
buildah config --author "Evan Carroll" --env "FOO=bar" -- "$ctr"
# Run a script inside the container
buildah run "$ctr" -- /bin/sh <<EOF
echo "This is just a regular shell script"
echo "Do all the things."
EOF
# Another one, same layer though
buildah run "$ctr" -- /bin/sh <<EOF
echo "Another one!"
echo "No excess layers created as with RUN."
EOF
# Commit this container as "myImageName"
buildah commit -- "$ctr" "myImageName"
Now you don't have to hack around with a Makefile. You have one shell script that does everything, and is far more powerful than a Dockerfile.
Side note, buildah can also build from Dockerfiles (using buildah bud), but this short coming is with the Dockerfile. So that won't help.