Path to becoming a good sysadmin
Emeka
Learn how to program in C at least well enough to write simple clients and servers, write a trivial threaded application using something like pthreads (just a couple ideas). Then start reading Advanced Programming in the Unix Environment. Really learn how to use Strace -- you should know what the difference is between a system call and a library call and be familiar with many of the common system calls you see in the output of that. You should understand the sockets API and file IO APIs. Should be able to understand socket and file descriptors and understand the output of lsof and be able to use it to debug problems.
Pick up the latest version of the Daemon book and learn how a Unix system is architected and what the different kernel subsystems are. Start poking around in the linux kernel sources. Use your C knowledge to make some toy modifications to the kernel (a /proc entry that echos back 'hello world' when you cat it for example). Read Unix Systems for Modern Architecture by Schimmel as a start if you want to go further here.
Take the same approach to the higher level aspects of systems. Your package manger is important so if you are on a RedHat system you should be able to take a trivial piece of C code that you wrote and properly package it so that you can build it, package it, and install it.
If you've built by hand or seen C packages built by hand you should have encountered 'configure; make; make install'. You should write a toy C program with a portability issue (find a Linux/FreeBSD portability issue and write a toy C program with that problem in it), and write an autoconf script so that you can run your code on either O/S.
Pick up either CFEngine, Puppet or Chef and learn how to use it (you can also add Salt and/or Ansible, but please don't consider yourself an expert if you don't understand the limitations of those two). Study Mark Burgesses Promise Theory.
Learn at least one high level scripting language that is in common use: Ruby, Python or Perl. You should also learn bash (and ideally learn old school /bin/sh and its differences with bash as well), but you cannot stop at just shell scripts.
Ideally you really learn how to program and write 10,000+ line object oriented programs, and write code that is tested. Learn what inheritance and composition are and why some software developers argue you should favor composition over inheritance. Learn the Law of Demeter and other principles.
Install and use something other than Linux to broaden your horizons a bit. FreeBSD at least. Solaris or one of the Solaris derived distros would be even better. Having a Mac as a laptop is also useful but I'm not sure it replaces playing with different server O/Sen.
Then, you definitely do also want Limoncelli's book and Nemeth's Unix and Linux System Administration Handbook and be able to configure a wide range of different systems apps (sshd, ntpd, SMTP mailers, apache, nginx, etc). If all you can do is install and configure apps, though, then you're no better than a scriptkiddie running scripts they download off the internet if you can't write them yourself. You won't understand what you're actually doing, and won't have a prayer of debugging some of the harder problems you can run into in architecting and debugging issue that come up in running those apps in a large and successful environment.
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