Friday, April 15, 2011

Passed 1/5 RHCA: EX442 System Monitoring and Performance Tuning

I passed the first exam,EX442 System Monitoring and Performance Tuning,in my road to RHCA (Red Hat Certified Architect) today.
Here are some tips I can share, I think, without violating confidential agreement.
Document Source.
EX442 is very heavy on theory, you simply can't remember every bit ( and  its different unit: kb,byte,sector, block, bit,million secs, secs). The key is to  get them in the system documents without Googling.
#Man pages e.g
man 5 proc
#man pages keyword search
$ man -k semget
semget               (2)  - get a semaphore set identifier
semget               (3p)  - get set of XSI semaphores
#man pages full text search
$man -w -K SEMMNI
/usr/share/man/man5/proc.5.gz
/usr/share/man/man2/semget.2.gz
#/usr/share/doc, full text search
$yum install kernel-doc
$grep -ri isolcpus /usr/share/doc/kernel-doc*/Documentation/.* 
/usr/share/doc/kernel-doc-2.6.18/Documentation/kernel-parameters.txt:   isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
#Other documentations in html/pdf/info/ps format
$rpm -ql valgrind | grep /usr/share
..
/usr/share/doc/valgrind-3.5.0/html/index.html
..
$elinks /usr/share/doc/valgrind-3.5.0/html/index.html
Make the change persistent
#always put the change in configuration file first, then run the command to activate the change 
- Startup service: chkconfig svc-name on; service svc-name start
- User auto start script: edit /etc/rc.local;  execute “/etc/rc.local”
- Kernel Parameter: edit /etc/sysctl.conf; execute “sysctl -p
- File system: edit /etc/fstab ; mount -a
- Kernel modules: edit /etc/sysconfig/modules/XXX.modules;   execute  “/etc/sysconfig/modules/XXX.modules”
Calculator:
#You got to know how to use bc.
#Always start with bc with “-l” option to support floating  point.
#e.g 1Gibit=131072KiByte
$ bc -l
1*2^30/1024/8
131072.00000000000000000000
#if there are too many to be added up, you got to use awk
#e.g  sum and average value calculated from 1 to 1000
$ echo {1..1000} | sed "s/ /\n/g" | awk ' {x=$1+x} END {print $1,x,x/NR } '
1000 500500 500.5
#convert  hexadecimal  value  to decimal  
#the hex letter must be in upper case
$echo -e " obase=10 \n ibase=16 \n 0F0" | bc -l
240
Time is essence, every minute counts, you got to master bash command line.
Check this: http://honglus.blogspot.com/2010/07/master-bash-command-line.html
lastly, the Exam day
 - take your RHCE number with you
 - there are a couple of tricky questions, I finished all, I thought I could get 90, but I only got 80. I don't know what went wrong.
 - Unlike RHCE exam, which has 2 sessions with a break for lunch, the EX442  only has 1 morning  session  last for 4 hours
 - Exam result will be emailed in 2 business days, but I got mine in 2 hours.


My Blog posts for EX442 study notes
Load kernel modules at boot time on Redhat/Centos Linux.
Tune Interrupt and Process CPU affinity
Understanding Linux CPU scheduling priority
Setup SNMP V3 USM with encryption.

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