Installing eAccelerator In Ubuntu Server
eAccelerator is a free open-source PHP accelerator & optimizer. It increases the performance of PHP scripts by caching them in their compiled state, so that the overhead of compiling is almost completely eliminated. It also optimizes scripts to speed up their execution.
“eAccelerator typically reduces server load and increases the speed of your PHP code by 1-10 times.” - eAccelerator
CentOS Firewall Init Script
I wrote a simple chkconfig compatible firewall init script for CentOS/RedHat/Fedora based Linux systems.
It will setup iptables firewall rules allowing anyone to access user defined ports (22,80 by default). It also has the ability to whitelist and blacklist IP’s. I’ve tested it with chkconfig on CentOS 5.
Print next few lines after pattern in AWK
Input data.txt is a collection report for XYZ corp group by different collection zones.
$ cat data.txt
Total Collection = $10291 {Fri May 8}
zone7 4500
zone8 3545
zone1 1200
zone0 900
zone3 70
zone5 67
zone11 9
Total Collection = $11847 {Sat May 9}
zone1 2800
zone3 2800
zone6 2567
zone8 2300
zone9 1200
zone12 90
zone11 90
Required: We need to find out the top 4 collection zones for each day from the above file. i.e. to print next 4 lines where the pattern “Total Collection =” is found (as the items are sorted on collection amount).
This is how we can achieve this using awk:
$ awk '/^Total Collection =/{c=4;next}c-->0' data.txt
zone7 4500
zone8 3545
zone1 1200
zone0 900
zone1 2800
zone3 2800
zone6 2567
zone8 2300
Now if we need to print the header line also, something like:
$ awk '/^Total Collection =/{c=4;{print}next}c-->0' data.txt
Total Collection = $10291 {Fri May 8}
zone7 4500
zone8 3545
zone1 1200
zone0 900
Total Collection = $11847 {Sat May 9}
zone1 2800
zone3 2800
zone6 2567
zone8 2300
And if you want to just print the date part as the header with top 4 collection zones.
$ awk -F "[{,}]" '/^Total Collection =/{c=4;{print $2}next}c-->0' data.txt
Fri May 8
zone7 4500
zone8 3545
zone1 1200
zone0 900
Sat May 9
zone1 2800
zone3 2800
zone6 2567
zone8 2300
Multiple FS in AWK
Sample file:
$ cat summary.txt A|Jan|clerk|02:45 B|Jan|Salesman|02:12 C|Jan|Accountant|03:12 A|Feb|clerk|01:10 B|Feb|Salesman|11:10 B|March|Salesman|3:10 C|Feb|Accountant|3:34
Output Required:
(First field)|(last field converted to minutes)
i.e. A|165 B|132 C|192 A|70 B|670 B|190 C|214
This is how we can specify two field separators (| and 
with FS in awk:
$ awk 'BEGIN{FS="[|,:]"; OFS="|"} {print $1,$(NF-1)*60+$NF}' summary.txt
How to change the hostname in Ubuntu
To change hostname in Ubuntu or any Debian variant Linux, modify the /etc/hostname and /etc/hosts.
sudo vi /etc/hostname
Change the old hostname to a new hostname.
sudo vi /etc/hosts
Also, change the oldhostname to a new hostname,
192.168.1.100 newhostname
After done, changing the /etc/hostname and /etc/hosts, you need to restart the hostname service.
sudo /etc/init.d/hostname.sh stop
sudo /etc/init.d/hostname.sh start
And then you log out from the shell and log in back. Once logged in, type
hostname
to check on the changes you have made for the hostname.
Ubuntu auto shutdown due to high CPU temperature
I use a laptop with Ubuntu 8.10 installed at work. While running the some high process, the CPU temperature get really high and its automatically shutdown the system. This thing happen every 2 or 3 days and its really annoying. The syslog showed the following error message:
ACPI: Critical trip point
Critical temperature reached (100 C), shutting down.
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