today's admins really don't know what they are doing, because they
don't do things from scratch and instead prefer package management.
I don't think an admin doesn't know what they are doing because they don't choose to use package management. There are many good reasons to use a package manager. I think they don't know what they are doing when they don't take to to understand; how their package management system works, how to build their own packages, or when they should build their own packages.
You can usually get commercial support from distributions like Redhat, and Ubuntu. You will find getting support is a lot easier if you are using the officially supported packages and not something you built yourself.
There are also a few commercial applications out there that require you use the official supported packages to actually make the product function.
If one were a UNIX/Linux
administrator, is it fair to use
package managers and is it trustworthy
The advantages of packages from official major distributions like Redhat, Ubuntu, Debian, and others is that lots of people are using them, there is strength in numbers. All major distributors offer the source you need to rebuild the package yourself. But if you don't trust the distributors to build a package, how can you even trust that there is nothing wrong in the source you downloaded? Do you have the skills to perform a code audit of the source code? Will you be able to detect a back door in the source or an exploitable bug? At a certain point you are going to have to trust someone because you probably won't have time to review every line of code that goes into an operating system.
on a job interview if asked to set up
Apache, does one reach for the source
or the package manager?
To answer the question you need to take some time to study the requirements. Frequently asking the right types of questions on your job interview will be more impressive then a simple response. You could also, just pick one method, and tell them a few reasons why that method is good, and a few reasons why that method is bad.
- Do they need a stable commercial support
- Do they need some unusual feature that is not enabled
- Do expect to support multiple servers in the future
- Do you have enough hosts running apache on your network that you can afford do your own monitoring of the upstream security feeds, and security lists.
I am a bit confused, as there are two
ways to install applications. One
being to configure and make from
source and the other from a package
You skipped the third, option. Build your own packages and maintain a local repository referenced by a package manager. Building your own packages, is preferable because what you have built will be part of the standard system. Someone familiar with the package manager will know how to uninstall it. They will be able to get information about it.