what does a linux administrator have to know?
do they have to know firewalls, routers, C++, shell, etc?
Is anyone here a linux administrator?
What exactly does a linux administrator do? do they fix linux?

I think it depends on the company. I work for a very large corporation, and we separate Server Administration from Network Infrastructure (firewall,routing). It's still good to know these things, but I don't think you need to be an expert on them. That said, things I do are:

Automate tasks via scripting, cron, at, or any means possible.
Administer all services on the server farm. (DHCP, DNS, NFS, SMB/CIFS, FTP, HTTP)
Coordinate all backups to a central SAN for the server farm. (mostly automated)
Coordinate all off-site tape backups (mostly automated, driving isn't)
Create few but handy small applications
Somewhat manage user accounts, but the service center does this also.
Print queue management for linux & AIX (smit), which is transitioning to service center
Terminal Services management
Desktop & Software deployment
** Auditing all server access & security ** (this should have been #1)
Server upgrades(hardware/software) & updates (software patches/kernel upgrades)

Know all the package managers. Its a positive and negative that we run every type of distro out there. We've got a few RPM based, Debian based, AIX, I've snuck in gentoo, and of course a bunch of Windows which I try to get rid of whenever possible.


Thats what I can think of. I'm sure theres more.

Did you get a lot of on the job trainning?

Trainging isn't a word used in my current company. I'd have to beat someone with a log to get them to write documentation. I read a lot, hang around forums like this one and try to keep myself up on the problems and solutions of the day to day grind.

If your looking for recommendation on training, buy VMware and a nice computer. Load several different distros and make them talk. Configure each as a separate function. Run through a gentoo/LSF type install, I learned a lot more through those two distros.