Update Dec 2021: I have written an updated article for installing Docker on focal 20.04
Docker is a container platform that streamlines software delivery and provides isolation, scalability, and efficiency with less overhead than OS level virtualization.
These instructions are taken directly from the official Docker for Ubuntu page, but I wanted to reiterate those tasks essential for installing the Docker Community Edition on Ubuntu bionic 18.04.
Uninstall older versions
sudo apt-get remove docker docker-engine docker.io containerd runc
Setup Docker Repository
# additional packages sudo apt-get install apt-transport-https ca-certificates curl gnupg-agent software-properties-common # add docker gpg key curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add - # add to repository list sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
Install Docker Community Edition
# update apt and install sudo apt-get update sudo apt-get install docker-ce docker-ce-cli containerd.io
This should have installed docker which is running under systemd. The docker engine logs should report “Started Docker Application Container Engine”.
journalctl -u docker.service
systemd will already have the service configured to start on boot, but if you want to check:
# check status sudo systemctl status docker.service # ensure start on boot sudo systemctl enable docker
Validate Install
# version installed sudo docker version # quick test of container sudo docker run hello-world
The docker run command from above should return a message like:
Hello from Docker! This message shows that your installation appears to be working correctly. To generate this message, Docker took the following steps: 1. The Docker client contacted the Docker daemon. 2. The Docker daemon pulled the "hello-world" image from the Docker Hub. 3. The Docker daemon created a new container from that image which runs the executable that produces the output you are currently reading. 4. The Docker daemon streamed that output to the Docker client, which sent it to your terminal.
Docker without sudo
You have have noticed that you had to run docker with sudo in the hello-world test above. That is because the Docker daemon binds to a unix socket which is owned by root. If you don’t want to force sudo access, then you can create a ‘docker’ group and add your user to it.
# group already created, but go ahead and make sure sudo groupadd docker # add self to docker group sudo usermod -aG docker $USER # reevaluate group memberships without exiting exec su -l $USER # should list 'docker' group now id
Logout, then log back in to make sure the membership is reevaluated (su – $USER). Then test by running hello-world again without sudo.
docker run hello-world
Docker via TCP
By default, the docker daemon listens on a local unix port owned by root (/run/docker.sock) which means your docker client will only work from the installed server and as sudo.
If you want to use a remote docker CLI to connect to this server, you need to consider the security implications and then you can create the x509 certs to secure the communication as described in the official docs.
Docker Compose
If you want to install docker-compose, you can do so with Python’s pip “sudo pip install docker-compose”, but you are going to get an older version. It is better to install the latest release (check for the latest version here).
# set latest version in variable cversion="1.24.1" # download sudo curl -o /usr/local/bin/docker-compose -L "https://github.com/docker/compose/releases/download/$cversion/docker-compose-$(uname -s)-$(uname -m)" # make executable sudo chmod +x /usr/local/bin/docker-compose # check version docker-compose -v
REFERENCES
fabianlee.org, Installing Docker CE on trusty and xenial
NOTES
backing storage for docker
sudo docker info | grep -i storage -A2