Docker Commands

Docker basics

Start a container in interactive attached mode: docker run -i -t ubuntu:16.04 /bin/bash

Detach from a container: Ctrl + P Ctrl + Q

Start a container in detached mode: docker run -d ubuntu:16.04 /bin/bash

View logs of a container: docker logs ContainerId

Start/Stop/Pause/Restart a container:

• docker start ContainerID
• docker stop ContainerID
• docker restart ContainerID
• docker pause ContainerID
• docker unpause ContainerID

List running containers: docker ps

List all containers: docker ps -a

List only container ids: docker ps -aq

List container ids not running: docker ps -aq -f status=exited

Delete a container: docker rm containerId

Delete all stopped containers:

• docker rm $(docker ps -aq status=exited)
• docker container prune

Automatically remove container once stopped: docker run -i -t --rm ubuntu:16.04 /bin/bash

Commit changes in a docker container: docker commit ContainerID username/repository

Create Docker Image

Build an image using Dockerfile: docker build -t sivaprasadreddy/myapp:1.0 .

Build an image using different Dockerfile name:

docker build -t busyboxplus:1.0 -f ./myfolder/MyDockerFile

View layers of a container: docker history ContainerId

Sample Dockerfile

# A basic apache server. To use either add or bind mount content under /var/www
FROM ubuntu:12.04

LABEL maintainer="siva@mail.com"

RUN apt-get update && apt-get install -y apache2 && \ 
    apt-get clean && rm -rf /var/lib/apt/lists/*

ENV APACHE_RUN_USER www-data
ENV APACHE_RUN_GROUP www-data
ENV APACHE_LOG_DIR /var/log/apache2

EXPOSE 80

CMD ["/usr/sbin/apache2", "-D", "FOREGROUND"]

Docker Instructions

FROM : The FROM instruction initializes a new build stage and sets the Base Image for subsequent instructions.

FROM <image>[:<tag>|@<digest>]

FROM ubuntu:latest

COPY: The COPY instruction copies new files or directories from <src> and adds them to the filesystem of the container at the path <dest>.

COPY <src> ... <dst>

COPY html /var/www/html

COPY httpd.conf magic /etc/httpd/conf/

ADD: The ADD instruction copies new files, directories or remote file URLs from <src> and adds them to the filesystem of the image at the path <dest>.

ADD <src> ... <dst>

ADD web-page-config.tar /

ENV: The ENV instruction sets the environment variable <key> to the value <value>.

ENV <key> <value>

ENV DEBUG_LVL 3

ENV APACHE_LOG_DIR /var/log/apache

WORKDIR : The WORKDIR instruction sets the working directory for any RUN, CMD, ENTRYPOINT, COPY and ADD instructions that follow it in the Dockerfile. If the WORKDIR doesn’t exist, it will be created even if it’s not used in any subsequent Dockerfile instruction.

WORKDIR <dirpath>

WORKDIR /var/log

EXPOSE: The EXPOSE instruction informs Docker that the container listens on the specified network ports at runtime.

EXPOSE <port>[/<proto>] [<port>[/<proto>]...]

EXPOSE 8080 8787

LABEL: The LABEL instruction adds metadata to an image. A LABEL is a key-value pair.

LABEL <key-1>=<val-1> <key-2>=<val-2> ... <key-n>=<val-n>

LABEL version="2.0" release-date="2016-08-05"

RUN The RUN command executes during build time.

RUN <command> (or) RUN ["<exec>", "<arg-1>", ..., "<arg-n>"]

• RUN echo "echo Welcome to Docker!" >> /root/.bashrc
• RUN ["bash", "-c", "rm", "-rf", "/tmp/abc"]

CMD: The CMD is to provide defaults for an executing container and runs when container starts. There can only be one CMD instruction in a Dockerfile. If you list more than one CMD then only the last CMD will take effect.

CMD <command> (or) CMD ["<exec>", "<arg-1>", ..., "<arg-n>"] (or) CMD ["<arg-1>", ..., "<arg-n>"]

//Dockerfile to demonstrate the behavior of CMD

FROM busybox:latest
MAINTAINER Siva <sivaprasadreddy.k@gmail.com>
CMD ["echo", "Dockerfile CMD demo"]

> docker build -t cmd-demo .

> sudo docker run cmd-demo

Output : Dockerfile CMD demo

> sudo docker run cmd-demo echo Override CMD demo

Output : Override CMD demo

ENTRYPOINT: An ENTRYPOINT allows you to configure a container that will run as an executable.

ENTRYPOINT <command> (or) ENTRYPOINT ["<exec>", "<arg-1>", ..., "<arg-n>"]

Only the last ENTRYPOINT instruction will be effective.

//Dockerfile to demonstrate the behavior of ENTRYPOINT

FROM busybox:latest
ENTRYPOINT ["echo", "Dockerfile ENTRYPOINT demo"]

> sudo docker build -t entrypoint-demo .

> sudo docker run entrypoint-demo

Output : Dockerfile ENTRYPOINT demo

> sudo docker run entrypoint-demo with additional arguments

Output : Dockerfile ENTRYPOINT demo with additional arguments

> sudo docker run -it --entrypoint="/bin/sh" entrypoint-demo

Output : /#

HEALTHCHECK: The HEALTHCHECK instruction tells Docker how to test a container to check that it is still working.

HEALTHCHECK [<options>] CMD <command>

Only the last HEALTHCHECK instruction will take effect.

HEALTHCHECK --interval=5m --timeout=3s CMD curl -f http://localhost/ || exit 1

Push image to DockerHub

$ docker images -a

$ docker login

Username: sivaprasadreddy

Password: my_password

• docker push sivaprasadreddy/myapp

Delete Image

• docker rmi sivaprasadreddy/myapp

Docker cleanup

Delete volumes

• docker volume rm $(docker volume ls -qf dangling=true)
• docker volume ls -qf dangling=true | xargs -r docker volume rm

Delete networks

• docker network ls
• docker network ls | grep "bridge"
• docker network rm $(docker network ls | grep "bridge" | awk '/ / { print $1 }')
• docker network prune

Remove docker images

• docker images
• docker rmi $(docker images -q) //delete all images
• docker rmi $(docker images --filter "dangling=true" -q --no-trunc)
• docker images | grep "none"
• docker rmi $(docker images | grep "none" | awk '/ / { print $3 }')

Remove docker containers

• docker ps -a
• docker kill $(docker ps -q)
• docker rm $(docker ps -qa --no-trunc --filter "status=exited")

Docker System Prune

$ docker system prune -a

WARNING! This will remove:
    - all stopped containers
    - all volumes not used by at least one container
    - all networks not used by at least one container
    - all images without at least one container associated to them
Are you sure you want to continue? [y/N] y

Resize disk space for docker vm

• docker-machine create --driver virtualbox --virtualbox-disk-size "40000" default