Information about command syntax:
Before we dive into learning about Docker commands and their many options, I want to
inform you of a change to the Docker CLI that happened in January 2017.
The number of commands and associated options have been increasing with each new
release of Docker. Docker decided that the complexity this was creating needed to be
addressed. So, with the release of Docker version 1.13 (Docker also changed the version
numbing scheme in 2017), the CLI commands have been divided into management
functional groups. For example, there is now a container management group of commands,
and an image management group of commands. This changes how you run Docker
commands. Here is an example of the use of the old and new run command:
# the new command syntax...
docker container run hello-world
# the old command syntax...
docker run hello-world
This change provides better command organisation, but also adds some verbosity to the
command line. It’s a trade-off. For now, as far as I know, the old command syntax still
works for all Docker commands, but for the rest of the examples in this book, I am planning
to use the new syntax. At least I’ll try, as old habits die hard.
One other note I would like to make here is that most command options have a short and
long format. I will try to share the long format as an option in my examples at least once so
you will know what the short version stands for. If you installed the Docker command-line
completion, it will be a helpful resource for remembering both the new Docker
management-based commands and the parameters that can be used with them. Here is a
look at the top-level command-completion help for the container commands:
The version command:
You have already used the docker –version command as a quick test to confirm that
Docker was installed. Now try the command without the dashes:
This version of the command gives you greater detail about the version of Docker installed
on your system. It is worth noting that the docker-compose command, which we will talk
about later, also has two versions of the version command—one with the dashes providing
a single-line response, and one without the dashes that delivers more details.