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Trying to learn docker here but I am a bit confused on what the difference is between docker.io and docker. Is docker.io the daemon server and docker the client? Why does the daemon need to run all the time?

Pithikos
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6 Answers6

48

You probably want docker.io.

The docker.io package is the Docker containerization software; whereas, the docker package is a tray plugin for docking applications to the desktop UI.

Running:

sudo apt-get install docker.io

installs package described as "Docker complements kernel namespacing with a high level API which operates at the process level." That is, the Docker everyone is usually thinking about when they say Docker.

Running:

sudo apt-get install docker

installs a package described as a "System tray for KDE3/GNOME2 applications"

Running:

sudo apt-cache search ^docker

displays descriptions of packages that start with the word "docker".

To make things more confusing, the snap package management tool uses the name docker to refer to the container, not the tray.

Dave Jarvis
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peteshaw
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19

docker-io is the deb package name used by Ubuntu distribution docker-engine is the deb package name from the official Docker Ubuntu distribution.

Probably you want docker-engine because the Ubuntu one is too old and buggy to be used. As of today Ubuntu has 1.6.2 and Docker registry has 1.12.0 !

In terms of Docker, 1.6.2 counts as stone-age.

sorin
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9

Docker is the name of the open platform for developers and sysadmins to build, ship, and run distributed applications. Docker.io on the other hand is the name of the package that you install in your Linux OS (i.e. Ubuntu). See this link here.

In terms of how it works, the Docker Engine consists of two parts: a daemon, a server process that manages all the containers, and a client, which acts as a remote control for the daemon. I would suggest you to try a quick demo they have on their site, located here.

From a usability standpoint, you invoke the Docker client anytime you use the docker command.

dandaman12
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8

Talking about Debian packages: docker.io is the name of the package provided by Debian/Ubuntu, while docker is the name of the package provided by docker.com.

Technically, these packages are built differently: for docker.io the build dependencies are fetched from Debian packages, while for docker, the build dependencies are in-tree, in the vendor directory.

If you want more details, I wrote a detailed blog post at: https://www.collabora.com/news-and-blog/blog/2018/07/04/docker-io-debian-package-back-to-life/

elboulangero
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7

It seems docker is just a symbolic link to docker.io:

> file $(which docker)
/usr/local/bin/docker: symbolic link to `/usr/bin/docker.io'

So we can assume that docker.io is both the daemon and the client process, just invoked with different flags I assume?!

Pithikos
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0

These are just all names: "docker.io" is name of package, and "docker" is name of the binary that interact with the daemon, which is "dockerd".

So when you run the command:

dpkg --listfiles docker.io

These files are listed:

/usr/bin/docker
/usr/bin/docker-init
/usr/bin/docker-proxy
/usr/bin/dockerd
Peter Teoh
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