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README.md

Docker

Table of Contents

Basic operations

## List running containers (formerly "docker ps")
docker container ls

# List all containers, running and stopped
docker container ls -a

# Check whether one specific container is running
docker container ls -a | grep container_name

# Stop all running containers
docker stop $(docker ps -q)

# List images
docker image ls

# List dangling images
docker images -f dangling=true

# Remove dangling images
docker image prune

# Remove dangling and unused images
docker image prune -a

# Follow the logs of a running container
docker logs -f <container_name>

# Enter and open a shell in a running container
docker exec -it <container_name> bash

# Print a list of the environment variables of a running container
docker exec -it <container_name> env

# Run a SQL query in a Postgres container
docker exec container-name bash -c 'psql -d database-name -U username --command "select * from users;"'

# Inspect an image (use /bin/sh for alpine images)
docker image pull <image_name>
docker run -t -i <image_id> /bin/bash

Customize containers list

# Show id, image, name and status of all containers
docker container ls -a --format "table {{ .ID }}\t{{ .Image }}\t{{ .Names }}\t{{ .Status }}"

# Show name, status and ports of all containers
docker container ls -a --format "table {{ .Names }}\t{{ .Status }}\t{{ .Ports }}"

# Filter containers by name
docker container ls -f name=container-name

Set a format to use it as a default in your ~/.docker/config.json:

{ "psFormat": "table {{ .Names }}\t{{ .Status }}\t{{ .Ports }}" }

Check if Docker Engine is running

Run:

docker version

If docker is running you will see:

Client: Docker Engine - Community
 Version:           ...
 [omitted]

Server: Docker Engine - Community
 Engine:
  Version:          ...
 [omitted]

If docker is not running you will see:

Client: Docker Engine - Community
 Version:           ...
 [omitted]

Error response from daemon: Bad response from Docker engine

Docker compose

Docker Compose is a way to configure docker containers together as a logical unit, define resources they all share and run containers together.

Some of the advantages include:

  • it keeps track of the container it starts (via labels). If you re-run docker-compose up -d without changes it won’t try to recreate any containers. If on the other hand you change a service a docker-compose up -d will recreate only that service and any service that depends on it.

  • with logs you can look at outputs of all involved containers merged together

  • ls covers just the containers stemming from the given compose-file.

Basic operations

# build
docker-compose build

# start
docker-compose up -d

# stop
docker-compose down --remove-orphans

# restart
docker-compose up -d --force-recreate

# rebuild
docker-compose down --remove-orphans && docker-compose build && docker-compose up -d

# clean up stale images
docker system prune

# prevent containers to start automatically
docker update --restart=no $(docker container ls -a -q)

# make one container start automatically
docker update --restart=always container_name

Useful links