Sunday, August 04, 2013

Another Red Hat Cert

Just last week I sat and passed the dreaded RHS333 Enterprise Network Security Services exams.  The instructor I had said that he only knew of one person who passed these exams first sitting, that was himself.  Now he knows two...  Not that this matters now, Red Hat are deprecating this certification in favour of a new one - that doesn't invalidate what I have done but going forward there will be a new certification to take the place of RHS333.  Regardless, I thought I would put down my thoughts on how to prepare for these exams as it does apply to pretty much all the Red Hat certifications just in case it helps someone else.

Firstly, I set up a lab environment which was just an extension of what I had described in Linux lab in the lap posting.  I just added a couple of new networks but made them routed instead of NAT type networks because it seemed like cross network traffic was being NATed with the IP address of the bridge interface which messed up the IP address based access control exercises.  On one network (the "good" network) I kickstarted a couple of machines to perform the exercises on, on the other network (the "bad" network) I kickstarted another machine to use as the "bad guy" in the lab exercises.  Then I would just run through the lab exercises until I could do them without even thinking, rebuilding all the machines before going over the labs again so I would have clean machines each time.

Here are a few more tips:

  • If yu have the book from the associated course then do all the exercises in the labs and do them well, make sure you understand what you are doing.  Don't skip any because anything that is covered in that book can be in the exam.
  • If a lab does not work then find out why, this is very important.  If you screw up you need to know why so either you can immediately recognise the error in the exam and fix it or just avoid making the error in the first place.  I have seen someone screw up a lab exercise and went on to do the same error in the exam - they failed because of this.
  • You don't have to memorise everything.  One of my instructors said, "this is an open man exam" meaning that you have all the man pages and documentation that is part of the standard RHEL distribution during the exam.  You can install whatever you like on the exam machines.  So, knowing where to look for information instead of rote memorisation is a valid tactic.  A lot of the time the samples provided in the man pages, sample configuration files or under /usr/share/doc are enough to get you going during the exam.  Just cut and paste from the documentation into your config file and adjust to suit the exam requirements.  So make it part of the exam preparation to hunt down where the trickier configuration documentation is kept so you can immediately bring it up during the exam.  Going hunting during the exam wastes precious time.
  • If you are having problems with something during the exam that other things do not rely on then just move on.  You can always revisit the question later, perhaps you will have worked out what to do or have time to spare to fiddle around.  By moving on you may able to pick up extra marks on things you can get working instead of beating your head against a wall fruitlessly
  • Do the chkconfig on immediately after installing or starting any new service that has been asked for.  If you are asked to provide a service then it must come up on reboot - ensure it does.  Same with selinux settings and other system settings - make sure they are permanent from the get-go, saves having to rework later.  Same with firewall settings, if iptables is running then add the appropriate rules for the service as you go - I usually just edit /etc/sysconfig/iptables directly and reload the service, saves typing because you can copy another existing line (though, command line history would be just the same...)
  • Make sure you are careful with file modes and ownership - I must admit to being sloppy with this during the exam and it does cost me
  • Leave enough time for a couple of reboots and carefully check everything that has been asked for still works after the reboot.  I have found that after drilling on the lab exercises I have plenty of time for this, in all the exams I have faced after starting really working on the lab exercises in my own time I have found that I can easily complete the entire exam with plenty of time to spare.
Hopefully this stuff will make a difference for someone else...

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