These steps cover how to install Debian Linux into your empty virtual or real machine. (The instructions are similar, but may vary somewhat, for Ubuntu Server.)
Download Debian 8 amd64, and burn it to a CD if installing on a real machine; otherwise, attach the downloaded ISO image to your virtual machine's CD/DVD drive.
Answer all the region related questions.
For hostname, enter a2server
Leave domain name empty.
Leave root password empty, and confirm that.
For the full user name, enter user1, and same for account name.
Choose apple2 as the password, and verify by retyping.
Choose your time zone.
Under Partition Disks, choose "Guided - use entire disk" (no LVM).
Choose SCSI1 (or whatever other disk appears), and then "All Files In One Partition", then "Finish Partitioning and write changes to disk", then confirm.
Select your download source.
If you require an HTTP proxy, enter it, or leave it blank if not.
Answer what you like for the package usage survey.
When prompted for software to install, keep in mind that A2SERVER does not require a desktop environment, so don't install one if you don't need one, and choose LXDE if you do, unless you really have a preference here.
Disable Print Server (unless you want it).
Ensure SSH Server and Standard System Utilities are selected, and Continue.
Choose yes to Install the GRUB boot loader to the master boot record
When done installing, the system will reboot.
When prompted, log in with username user1 and password apple2. If you installed a desktop environment, open a terminal window.
sudo sed -i '0,/-eq 0/s/-eq 0/-ge 0/' /etc/profile
When you're back at the prompt, type
sudo shutdown -h now which will turn off the (virtual) machine.
Recommended: If you are using a virtual machine, take a snapshot so you can return to this point if necessary.
A2SERVER home page