Docker install, docker command and Issues

Docker is a set of platform as a service products that use OS-level virtualization to deliver software in packages called containers. The service has both free and premium tiers. The software that hosts the containers is called Docker Engine. 

Step 1: Uninstall old versions and Update OS

Older versions of Docker were called docker, docker.io, or docker-engine. If these are installed, uninstall using following command:

 sudo apt-get remove docker docker-engine docker.io containerd runc

It’s OK if apt-get reports that none of these packages are installed.

Check if the system is up-to-date using the following command:

sudo apt-get update

Step 2: Install Docker

Now, Install docker by the following command- 

sudo apt install docker.io

Step 3: Install all the dependency packages 

sudo snap install docker

Step 4: Check the version

Before going to work with Docker, check the version installed using the following command:

docker --version

This will shows as like if Docker is installed successfully 

Docker version 20.10.12, build e91ed57

Step 5: hello-world Image: 

Pull hello-world image from the Docker hub using the following command:

sudo docker run hello-world

Here, hello-world is the docker image present on the Docker hub.

This is all about installing docker on Ubuntu.

Docker Commands:

There is some command regarding Docker: 

• Check Docker pulled images

By following command, you can check the docker image has been pulled and is present in your system -

sudo docker images

• Display all the containers pulled

To display all the containers pulled, use the following command:

sudo docker ps -a

• Check for containers 

To check for containers in a running state, use the following command:

sudo docker ps

Issues: 

Issue 1: 

If following comment executing, shows message: permission denied,  

docker image ls

Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get "http://%2Fvar%2Frun%2Fdocker.sock/v1.24/images/json": dial unix /var/run/docker.sock: connect: permission denied

For remedy this,  you have add group: 

 sudo groupadd docker

 groupadd: group 'docker' already exists

sudo usermod -aG docker $USER
newgrp docker

after that, run command again

docker image ls

Output: 

REPOSITORY    TAG       IMAGE ID       CREATED        SIZE
hello-world   latest    feb5d9fea6a5   3 months ago   13.3kB
php           5.6-fpm   3458979c7744   2 years ago    344MB

...............

Thanks