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?
If you are using Ubuntu, and you do an
sudo apt-get install docker
You will get a package described as a "System tray for KDE3/GNOME2 applications"
If on the other hand, you do
sudo apt-get install docker.io
You will get a package described as "Docker complements kernel namespacing with a high level API which operates at the process level." i.e. the Docker everyone is usually thinking about when they say Docker.
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.
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
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
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/