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Another neat default in Ubuntu Server is that it automatically configures most 
packages to have their daemons start up and also be enabled so that they start with 
each boot. Using the earlier example of 
apache2
, the 
apache2
 service will start and 
the application will automatically start running as soon as you install the package. 
This may seem like a good idea for the sake of convenience, but not everyone prefers 
this automation. As I've mentioned, the more packages installed on your server, the 
higher the attack surface, but running services (also known as daemons, or units) 
are each a method of entry for miscreants should there be a security vulnerability. 
Therefore, some distributions don't enable and start daemons automatically when 
you install packages. The way I see it, though, you should only install packages you 
actually intend to use, so it stands to reason that if you go to the trouble of manually 
installing a package such as Apache, you probably want to start using it.
When you install a package with the 
apt
 keyword, it searches its local database for 
the package you named. If it doesn't find it, it will throw an error. Sometimes, this 
error may be because the package isn't available or perhaps the version that 
apt
 
wants to install no longer exists. Ubuntu's repositories move very fast; new versions 
of packages are added almost daily. When a new version of a package is added, 
its older equivalent may be removed. For this reason, it's recommended that you 
update your package sources from time to time. Doing so is easy, using the following 
command:
sudo apt update
This command doesn't actually update any packages; it merely checks in with your 
local mirror to see if any packages have been added or removed and updates your 
local index. This command is useful because installations of packages can fail if your 
sources aren't up to date. In most cases, the symptom will be that 
apt
 errors out of 
the process when it can't find a package it's looking for.
Removing packages is also very easy and follows a very similar syntax; you would 
only need to replace the 
install
 keyword with 
remove
:
sudo apt remove
And, just like with the 
install
 option, you can remove multiple packages at the 
same time. The following example will remove three packages:
sudo apt remove
If you'd like to not only remove a package but also wipe out its configuration, you 
can use the 
--purge
 option:
sudo apt remove --purge

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Chapter 3