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2021-09-19 | Personal | NonRoot |
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Configuring docker
title: Summary
collapse: open
This note runs through [docker](https://docker.com), a free tool to create containers to run independent applications.
style: number
Installation
Program installation
- Prerequisites
sudo apt update
sudo apt install curl apt-transport-https ca-certificates software-properties-common
If the packages are already installed and to the latest version, the OS will skip.
- Pull the software signature key & image
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key ad
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable"
- Install docker
sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io
- Test install
sudo systemctl status docker
Configuring user permissions
Users with sudo rights need to be added to the 'docker' group for being able to instruct docker:
sudo gpasswd -a (username) docker
sudo newgrp docker
Installing docker-compose
Docker-compose is a script generatir enabling leaner execution and update of each container. The following commands install the wizard.
sudo curl -L "https://github.com/docker/compose/releases/download/1.29.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
File permissions need to be changed for docker-compose to be executable:
sudo chmod +x /usr/local/bin/docker-compose
Installation can be checked as follows:
sudo docker–compose --version
docker elements
docker network
In order for docker to work, each container needs an internal IP address. This is defined by an internal docker network as follows:
sudo docker network create --driver=bridge --subnet=xxx.yyy.zzz.0/24 --gateway=xxx.yyy.zzz.1 dockernet
x, y, z to be defined by the user.
Creating containers
Containers are created through docker-compose. Tutorial exist for each application to run in docker. In short:
- A directory for the app must be created
- A yaml file for docker-compose must be created in the folder
- The docker-compose command for initialisation must be run from the folder:
sudo docker-compose up -d
Maintaining containers
Maintaining containers with docker is arduous and easier to do with docker-compose. Easiest is to create aliases in the .bashrc of home directory by adding:
alias dc-up='sudo docker-compose --compatibility up -d' alias dc-update='sudo docker-compose pull && sudo docker-compose --compatibility up -d' alias dc-update-all='for d in ./*/ ; do (cd "$d" && dc-update); done'
To the following file:
~/.bashrc
The command needs to be run periodically.
Updating containers
For updating containers, just amend the docker-compose file and run the following command to preserve the mounted data:
docker-compose up -d
From within the container folder.
Update environment variables
Docker does not have a standard way to update environment variables, and requires to take down and then re-initialise a container with the appropriate variable fed in the run script. To avoid that, the followong steps can be taken:
- stop docker
sudo systemctl stop docker
- Edit the json config file
Location: /var/lib/docker/containers/(container id)/config.v2.json
Within the 'Env' declaration, add the requested data field:
"DATA_FIELD=data_value"
- Restart docker
sudo systemctl start docker
Basic commands
List containers
docker container ls
Execute commands in container
docker exec -it -u (username) (command)