systemd services like containerd do not read the environment variables configured from the shell. This is a problem when you are working behind a proxy server.
Articles on Linux
A quick reference of commonly used docker commands.
You are already using Ansible for configuring Linux servers. Here's how to use Ansible for verifing configurations.
Using SSH key-based authentication and SSH config file, you can easily push code from multiple GitHub accounts in the same computer.
While installing Ubuntu Server if you let the installer take care of the disk partitioning, the root volume will not occupy the entire disk by default. But, Ubuntu uses LVM so you can easily extend the volumes, if you run out of space.
Get familiat with Docker with this hands-on guide.