So I'm going to be contrary and disagree with your linux section. A few points. 1) I didn't learn anything from linux from scratch that really helped me in an actual enterprise environment. If you want to get familiar with the way that files are organized just do a regular arch linux install. Unless you are working on embedded systems the linux from scratch isn't that good. 2) The RHCSA actually is well before /u/iConrad's list. Infact here is how I would do it.
1- http://www.amazon.com/RHCSA-Linux-Certification-Study-Edition/dp/0071765654 <---- Michael Jang's RHCSA/RHCE guide for RHEL6. Use this with CentOS6 or SL6. This builds those basic skills. Alternatively if you are pursuing certs go ahead and do the RHEL7 version of the material. Jang's isn't out yet but the other ones are fine
2- Learn systemd and docker - these guys are the big difference from RHEL6 and RHEL7 certification.
3- Take the RHCSA exam.
4- Do iConrad's list
5- Revisit the RHCE portions of the study guides
6- Take the RHCE exam
7- Look at AWS/Azure certs.
I'm sure others will disagree with me but that's how i'd go about it. Although I did have the advantage/disadvantage of having come to linux after doing Solaris for awhile so my path might be underestimating the rigor of the RHCSA but I thought it was very basic levels of knowledge.
Just a tip regarding Linux experience - play with CentOS 6 preferably over 7 as it is still the most common enterprise deployment (7 is still too fresh and 6 is supported until 2020 so it's not going away just yet). The RHCSA/RHCE study guide book is a great resource and will give you a great grounding in the basics (even just the first half which covers the RHCSA). Yes it is RHEL focused, but the base concepts are the same in most *nixes.
Edit: This book: http://www.amazon.com/RHCSA-Linux-Certification-Study-Edition/dp/0071765654 (nice and cheap now that the book for 7 is out)
I used this for my study and passed with a great score. http://www.amazon.com/RHCSA-Linux-Certification-Study-Guide/dp/0071765654
You need to be more specific,
*what have you tried so far? *which ISO have you used to install CentOS? *what exactly are you having problems with?
http://certcollection.org/forum/forum/81-linux/ is very good for training and learning what you need to know.
This is usually considered the best book for RHCSA for CentOS 6
This one has a lot of basic skills and is explained very well.
Well, you could get yourself a RHCSA prep book (linked to the one i have and found useful) and go through all of the exercises. The way I learned was basically to set up my own servers, either physical or virtual, at home, and run them. I think FreeBSD, Gentoo, and Slackware were the most beneficial to me in that they don't really make choices for you, so you have to configure things for yourself which forces you to read the documentation and learn. They all have excellent documentation, btw. If you want to go a step further, linux from scratch will really teach you about the operating system from the ground up.
From there, come up with little projects for yourself. Like making a home NAS, setup NFS and Samba shares, install XBMC on a HTPC and hook it up to your tv to stream movies and music. Setup a webserver and owncloud. Stuff like that.
Best book out there if you want to get up to speed on RHEL for the RHCE exam http://www.amazon.com/RHCSA-Linux-Certification-Study-Guide/dp/0071765654/ref=sr_1_1?ie=UTF8&qid=1325116861&sr=8-1
I agree, at least inasmuch as knowing (3) isn't absolutely dependent on knowing (2). But to really hit the "intersection of theory and application" bit, you need to have spent some time doing sysadmin things, especially since they teach you how things break. Having developer-tier competence without sysadmin-tier puts you more on the theoretical end of the spectrum.
This is unfortunate, since there's such a division in the industry between sysadmins and developers that most developers never get a good feel for what it takes to keep a system running. If your software runs on a Linux server, and you know the sysadmin-type and developer-type parts of Linux usage, that gives you the ability to do systems programming and build actual applications (as opposed to just the Perl scripts that a mere sysadmin will write).
Just my two cents. If you want to get a feel for the sysadmin side of things, knowing the kind of stuff covered in the RHCE exams couldn't hurt. Those certs are expensive, so I wouldn't suggest actually getting them (unless somebody pays for it), but if you're already competent at the low-level bits then flipping through an exam study guide should take you at most a weekend. More like a few hours if you know the core concepts and skip the GUI bits.
Then when you have to make a package out of your application, or write a network service that does enterprise-grade authentication, you won't be lost knowing where to start. The actual knowledge contained isn't very much, and you'll have done things like configured Apache and samba - so you can emulate those services when making your own applications.
http://www.amazon.com/RHCSA-Linux-Certification-Study-Edition/dp/0071765654/
Just buy this. It's not going to give you comparisons, but it'll tell you how to do most tasks in RHEL.
I'm working my way through Damian Tommasino's RHCSA/RHCE book right now. It's fine for me (I've got some experience), but a lot of people on Amazon hate it.
This book has better reviews.
As others have said, Linux+/LPIC-1 is decent, but Red Hat certifications are where it's at.