Docker (and docker-compose) on Rocky Linux

I am not a great fan of Docker, but I have to use somehow for several activities. So far, I’ve always used Docker on Ubuntu based distributions, were installing a decent docker and docker-compose version was quite simple and did not require any particular repository to set up. This is not the case with Rocky Linux. First of all, to get docker running on Rocky Linux there is the need to install a particolar repository: 

% sudo dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo


Then, you can install the packages docker-ce and docker-ce-cli to get almost all the commands and machinery up and running. In particular, you have to: 

sudo dnf -y install docker-ce docker-ce-cli


However, the above is not going to give you the docker-compose, and you need also to install the following: 

% sudo dnf install docker-compose-plugin


But, unluckily, this is not going to give you the docker-compose command again: on Rocky Linux docker-compose does not exist and compose is a subcommand of docker, that means it has to be invoked as docker compose. This is clearly a problem for scripts using docker-compose that need to be adjusted to use docker compose instead, and I don’t know the reasons for this non-portable choice! Last, in order to run docker you have to start the service: 

% sudo systemctl --now enable docker


How to change docker-compose to docker compose

There are different ways to switch between a version and the other. The simplest one is to create a shell alias: 

% alias docker-compose='docker compose'


Another approach is to test, in your script, for the existance of docker-compose or docker compose: 

DOCKER_COMPOSE=$(which docker-compose 2>/dev/null)
if [ ! -x "$DOCKER_COMPOSE" ]; then

    # try to run docker compose
    `docker compose > /dev/null 2>&1`
    if [ $? -eq 0 ]; then
		DOCKER_COMPOSE="docker compose"
    fi
fi


In the end, the variable DOCKER_COMPOSE will contain the correct command to invoke, so you are free for instance to run $DOCKER_COMPOSE build and the script will translate it to either docker-compose build or docker compose build according to which command has been found.

Conclusions

Docker is not as portable as it may sound: apparently different distributions use different approaches to some commands. Personally, I do prefer the Rocky Linux approach (i.e., adding commands to docker), but in anycase this is not a portable approach.

The article Docker (and docker-compose) on Rocky Linux has been posted by Luca Ferrari on October 9, 2023

Tags: linux , docker