General
You can always upgrade from LTS to LTS, in your case that would mean:
- upgrade from 12.04 to 14.04 and then
- upgrade from 14.04 to 16.04
As far as i know there is no supported upgrade from 12.04 to 16.04 directly.
Following this approach there is no need for your 16.04 medium
As always, consider creating a backup of your critical files before you start.
Limit to LTS
The way to limit upgrades to LTS without a GUI is to change the value of Prompt
in /etc/update-manager/release-upgrades
.
Set it to
[DEFAULT] Prompt=lts
The possible values are
never: Never check for a new release.
normal: Check to see if a new release is available. If more than one new release is found, the release upgrader will attempt to upgrade to the release that immediately succeeds the currently-running release.
lts: Check to see if a new LTS release is available. The upgrader will attempt to upgrade to the first LTS release available after the currently-running one. Note that this option should not be used if the currently-running release is not itself an LTS release, since in that case the upgrader won't be able to determine if a newer release is available
How to upgrade
For both upgrade processes you should always update the current system via
sudo apt-get update
sudo apt-get upgrade
Then start the upgrade via
sudo do-release-upgrade
or - SPECIAL CASE - for development versions (which is valid for upgrades from 14.04 to 16.04 until 16.04.1 was released):
sudo do-release-upgrade -d
If do-release-upgrade
command is not found, install it:
sudo apt-get install update-manager-core
Best Answer
What's the difference between desktop and server?
1) The first difference is in the CD contents. The "Server" CD avoids including what Ubuntu considers desktop packages (packages like X, Gnome or KDE), but does include server related packages (Apache2, Bind9 and so on).
2) The Ubuntu Server Edition installation process is slightly different from the Desktop Edition. Since by default Ubuntu Server doesn't have a GUI, the process is menu driven, very similar to the Alternate CD installation process.
3) Ubuntu server installs a server-optimized kernel by default (the commands you mentioned should do it).
4) Ubuntu Desktop will receive 3 years of support, while Ubuntu Server will be supported for 5 years.
Can I convert the Desktop installation to server?
You can use apt-get to install the packages you need like Apache and Bind9 for example.
Reference: 1.