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Docker Reference

(no brackets in commands unless specified)

Setup

• Install Docker

  • curl -fsSL get.docker.com -o get-docker.sh && sh get-docker.sh
  • obviously, if you want to inspect the shell file before running it, you can modify the command and look it over
• Download an image
  • docker pull [image-name]

Containers

• Create a container and run it in background

  • docker run -d --rm -p 8080:80 --name [createANameHere] --network [networkName] [image-name] [commandToRun]
  • -d means detach and will run it in the background
  • --rm will delete the container after it has stopped
  • -p [containerPort]:[hostPort] connects the port on the host the port on the container NOTE this can (and DOES in the case of ufw) override firewall settings! only use for services you want exposed on the host's network! (use docker network for internal communication between containers)
  • --network and its followup argument is optional, but recommended for production (more on networks below)

• Create a container and use it interactively

  • docker run -it --rm --name [createANameHere] [image-name] [commandToRun]
    • for example docker run -it --rm --name SwiftTest swift:5.7

• List containers

  • docker container ls -a
  • -a lists all containers, not just those running currently

• Connect to existing, running container's main process

  • docker container attach [containerName]
  • Note: The attach command will display the output of the ENTRYPOINT/CMD process. This can appear as if the attach command is hung when in fact the process may simply not be interacting with the terminal at that time. ref

• Run a new process in an existing, running container (best not to do in production)

  • docker -exec -it [containerName] [command (like /bin/bash)]
• Detach from a docker container
  • Hit Ctrl-p and then Ctrl-q
  • can be done without releasing Ctrl key

Networks

• Create a network

  • docker network create --driver bridge [newNetworkName]
  • --driver is optional as bridge is the default value
    • options:
      • bridge - default - can communicate with others on same docker network as well as the internet
      • overlay - can communicate with other docker hosts - untested
  • containers can communicate with each other using container names on custom networks
    • alternatively, on the default network, you can only communicate with other containers via their ip
  • containers CANNOT communicate with containers on the same host UNLESS they share a network
  • containers created without specifying a network are automatically connected to the network named bridge (not to be confused with the driver named bridge)
  • containers can only be connected to one network at instantiation, but more can be added once created

• list networks

  • docker network ls

• connect existing container to a network

  • docker network connect [networkName] [containerName]
• inspect a network
  • docker network inspect [networkName]

Dockerfile

used to create docker images

• a very basic dockerfile looks like this:

  FROM [upstreamImageName]
  MAINTAINER Your Name (email@address.com)
  RUN [commandToRunDuringImageSetup]
  COPY [local file or directory] [/path/to/a/conf/directory/in/image]
  ENTRYPOINT ["command" , "arg1", "arg2", "..."] #brackets actually used here
  CMD ["altPlaceForArg1", "altPlaceForArg2"] #brackets also here
  EXPOSE [port exposed to host]

  • example:

    FROM ubuntu:latest
    MAINTAINER Your Name (email@address.com)
    RUN apt update
    RUN apt install nginx
    COPY default.conf /etc/nginx/conf.d/
    ENTRYPOINT ["/usr/sbin/nginx" , "-g", "daemon-off;"] #brackets actually used here
    EXPOSE 80

• build this image (while in the same directory:

  • docker build -t my-nginx-server:latest .
  • -t means to tag the image
• run this image
  • docker run -d -p 80:80 --name webserver my-nginx-server
  • go to your server's ip in a browser to see the nginx default install landing page

Compose?

deploys containers via yaml script

• docker compose used to be installed via a separate standalone executable, but now it's included in the default docker install. You can use it with the docker compose command

this document last modified: November 18 2022 21:31

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