Can Ubuntu Desktop "become" Ubuntu Server?
Solution 1:
The differences are just in what's bundled as a default packaging to make things easier. In reality the difference between a server and workstation are just the purpose they're used for; Linux is Linux in either case (indeed Windows NT variants were largely just differences in packaged tools/dll's and some registry hacks to enforce licensing differences for how much you paid for your license...the kernel was the same and the base OS was the same).
In other words, Ubuntu Server and Ubuntu Desktop are two sides to the same coin. Server was just meant to run by default with some packages to make it easier to set up a LAMP server or file server by default while desktop looks nicer and has office tools/GUI/etc. for desktop users.
Solution 2:
As everyone stated, you just need to apt-get the correct packages to make your Ubuntu Desktop "become" an Ubuntu Server.
However, there are differences in the installation process when you opt for the Server edition. For instance it allows you to install Ubuntu on a LVM volume, which the Desktop CD doesn't support.
Solution 3:
That's correct. The default install of a desktop installs the ubuntu-desktop meta-package, which pulls in the normal GUI interface stuff. It also includes metapackages ubuntu-minimal and ubuntu-standard, which together comprise the basic Linux utilities.
Play around with the program tasksel if you would like to deal with server stuff; also note that Ubuntu has a separate server install CD if you wish to use that.
Solution 4:
Correct... Its basically a package thing.
I know of several folks who install SERVER version then add on the desktop GUI for ease of use.
Play around with it... have fun. :-)
Note: I'm not recommending one way or another. I personally like my servers to run with as little as possible. Less moving parts usually means less that can break.
Solution 5:
The best answer is correct, but when I was googling this I expected to find an instruction of how to remove 'desktop' packages (gnome, xserver, etc) from my Ubuntu installation. I've found that I can use tasksel to remove ubuntu-desktop packages:
sudo apt-get install tasksel
sudo tasksel remove ubuntu-desktop
sudo tasksel install server
I did some mess with acpid and got the following error:
acpid.service: Got no socket.
in the systemctl status acpid output. I've fixed this with just:
systemctl stop acpid
systemctl stop acpid.socket
systemctl stop acpid.path
systemctl start acpid