Docker – petrhurtak.com

This article assumes basic Docker knowledge and is more of a shortlist of useful commands rather than beginners introduction.

Dockerfile

First, you will need a Dockerfile file in your repository. Here is how simple one might look like.

# Base image
FROM node:12

# Working directory inside of the container
WORKDIR /app/

# Copy stuff inside of the container. The left path is the host OS, the
# right path is inside of the container relative to the WORKDIR.
COPY ./package.json .
COPY ./index.js .

# Run scripts or install dependencies
RUN npm install

# Set environment variables
ENV NODE_ENV production

# What command/binary to run when the image is started
ENTRYPOINT ["node"]
# What default arguments to supply to given ENTRYPOINT
CMD ["index.js"]

Create commands

# Build image
#   -f/--file  Path to Dockerfile, default is 'CWD/Dockerfile'
#   -t/--tag   Name and optionally a tag in the 'name:tag' format
docker build .

# List images
docker image ls

# Run container
#   -d/--detach   Run container in background and print container ID
#   -p/--publish  Connect container port to host OS port, eg: '-p 8000:8000'
docker run <IMAGE ID>

# List running containers
#   -a/--all  Show all containers, default shows just running
docker ps

# Run a command in a running container
#   -i, --interactive  Keep STDIN open even if not attached
#   -t, --tty          Allocate a pseudo-TTY
docker exec -it <CONTAINER ID> /bin/sh

Cleanup commands

# List containers
#   --all  Shows also stopped ones
docker ps --all

# Stop the running container
docker container stop <CONTAINER ID>

# Remove container
#   --force  Remove running containers
docker container rm <CONTAINER ID>

# List images
docker image ls

# Remove images
docker image rm <IMAGE ID>

Example workflow

# Take Dockerfile and build an image
$ docker build .
Sending build context to Docker daemon  2.008MB
...
Successfully built ea5c328aef35

# List images
$ docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED              SIZE
<none>              <none>              ea5c328aef35        About a minute ago   919MB

# Run the container
$ docker run ea5c328aef35
Example app listening at http://localhost:8000

# List running containers
$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED              STATUS              PORTS               NAMES
08d6c527fe82        ea5c328aef35        "node index.js"     About a minute ago   Up About a minute                       mystifying_hellman

# Connect to running container and execute command inside of it.
# Command we execute is '/bin/bash', so we
# can use bash to explore container contents.
$ docker exec -it 08d6c527fe82 /bin/bash
root@08d6c527fe82:/app# ls
index.js  node_modules  packag
root@08d6c527fe82:/app# exit

# Stop and remove the running container
$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
08d6c527fe82        ea5c328aef35        "node index.js"     3 seconds ago       Up 3 seconds                            festive_lehmann

$ docker container stop 08d6c527fe82
08d6c527fe82
$ docker container rm 08d6c527fe82
08d6c527fe82

$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

# Remove the image
$ docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
<none>              <none>              ea5c328aef35        48 minutes ago      919MB

$ docker image rm ea5c328aef35
Deleted: sha256:ea5c328aef35edf1a19e10fa5d7a62f11d9e61f76db01d86c7c94da5f7432185
...