I am typing
$ sudo apt install docker
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
Use 'sudo apt autoremove' to remove it.
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 12.2 kB of archives.
After this operation, 65.5 kB of additional disk space will be used.
Get:1 http://us-central1.gce.archive.ubuntu.com/ubuntu xenial/universe amd64 docker amd64 1.5-1 [12.2 kB]
Fetched 12.2 kB in 0s (132 kB/s)
Selecting previously unselected package docker.
(Reading database ... 158032 files and directories currently installed.)
Preparing to unpack .../docker_1.5-1_amd64.deb ...
Unpacking docker (1.5-1) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up docker (1.5-1) ...
The program 'docker' is currently not installed. To run 'docker' please ask your administrator to install
the package 'docker.io'
synhedionn@instance-7:~/POUB/docker-tomcat-tutorial$ sudo docker
sudo: docker: command not found
So it says installed, but docker keyword is not available.
What happens ?