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I'm trying to install docker on my Ubuntu 20.04. Trying install docker with apt-get and snap:

sudo apt-get install docker

Output:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  wmdocker
The following NEW packages will be installed:
  docker wmdocker
0 upgraded, 2 newly installed, 0 to remove and 6 not upgraded.
Need to get 0 B/14.3 kB of archives.
After this operation, 58.4 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Selecting previously unselected package wmdocker.
(Reading database ... 193518 files and directories currently installed.)
Preparing to unpack .../wmdocker_1.5-2_amd64.deb ...
Unpacking wmdocker (1.5-2) ...
Selecting previously unselected package docker.
Preparing to unpack .../archives/docker_1.5-2_all.deb ...
Unpacking docker (1.5-2) ...
Setting up wmdocker (1.5-2) ...
Setting up docker (1.5-2) ...
Processing triggers for man-db (2.9.1-1) ...

If I run docker command I get error:

a@ubuntu:~$ docker

Command 'docker' not found, but can be installed with:

sudo snap install docker     # version 19.03.11, or
sudo apt  install docker.io  # version 19.03.8-0ubuntu1.20.04.1

See 'snap info docker' for additional versions.

Why system can't find docker command?

Then I tied snap:

sudo snap install docker

And docker command run fine.

Why I can install docker with snap and can't with apt-get ?

vico
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1 Answers1

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Because that docker is not the docker you expected. docker is the package name of system tray for KDE3/GNOME2. You can verify that by visiting Ubuntu package search or by running

apt show docker

The error message you got while running docker from terminal gives a brief idea about this confusion.

To install the docker you expected, refer to official documentation or see How to install docker community on Ubuntu 20.04 LTS?

Kulfy
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    `docker.io` is Docker package in APT! – N0rbert Dec 05 '20 at 07:02
  • @N0rbert Though Ubuntu's official repository contains docker as `docker.io`, [docker's official documentation](https://docs.docker.com/engine/install/ubuntu/) states, *"Older versions of Docker were called `docker`, `docker.io`, or `docker-engine`"*. And the very first step is to remove them. ¯\\_(ツ)_/¯ Anyway with Docker's repository you can have latest version in Xenial Xerus which is not the case with `docker.io`. – Kulfy Dec 05 '20 at 07:28
  • Agree that *`docker`* name confuses the user. But `docker.io` is working normally when installed :) – N0rbert Dec 05 '20 at 07:41
  • If it is not the real docker how it can pull images, and run them? I just installed the docker via snap `sudo snap install docker` and it can run hello-world `docker run hello-world` – AVarf Apr 07 '22 at 09:38
  • @AVarf I believe you misread the question as well as answer. In the question as well, vico confirmed that snap version was working fine which I never denied. My answer was related to the docker installed using APT. – Kulfy Apr 07 '22 at 09:40
  • I am sure I read the Q correctly since I have the same problem and because of some firewall I can't install docker via apt but I am able to install it via snap. Maybe I misunderstood your answer. The only thing I want to know is what are the differences between docker installed via apt and snap? One I could find is when installed via snap there is no docker.service (`Unit docker.service could not be found.`) – AVarf Apr 07 '22 at 09:48
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    @AVarf APT installs deb packages. Snaps and debs differ functionally. See https://snapcraft.io/blog/a-technical-comparison-between-snaps-and-debs. For service not found issue, on a quick Google search, I found this https://askubuntu.com/q/977961 – Kulfy Apr 07 '22 at 09:57