Κατηγορία: System Administration

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Red Hat Certificate Exam Preparation

Marios asked me to elaborate a little on the Red Hat Certification Exams and my preparation.

I found the lab based exams much better than other multiple choice exams. It doesn’t matter if you do something using the command line, a gui tool, or if you write a program yourself to do the job. It’s real world simulation!

The preparation was self-study using the following:

No book covering RHEL6 existed while I was preparing, but I believe one is available now (ISBN 0321767950) and others are on their way (e.g. ISBN 0071765654).

I also recently discovered OpenRHCE by @texastwister, an effort to collaboratively prepare study materials to help candidates achieve Red Hat’s RHCE certification, under a CC license.

I found the journey of answering all the above quite a rewording experience. I have learned new things and I can definately troubleshoot SELinux issues faster than before ;-)

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HDD Power-on hours

All modern hard disks are S.M.A.R.T. enabled. «SMART is a monitoring system for hard disks to detect and report on various indicators of reliability, in the hope of anticipating failures».

Most people never pay attention to the numbers, some people only pay attention to the templerature, and if something bad happens (a failure) then they give some attention to the error counters.

But here are two counters that I found very interesting: Power_On_Hours and Power_Cycle_Count.

A hard disk used in my desktop machine

Power_On_Hours 7566
Power_Cycle_Count 314

A hard disk used in a server machine

Power_On_Hours 45030
Power_Cycle_Count 28

To see this info about your hard disk, use «smartctl -a /dev/sda | grep Power».
smartctl is part of the smartmontools package in most linux distros.

This was triggered by the following tweet