Benchmarking Your Site with ‘http_load’
http_load is a stunningly useful HTTP benchmarking utility that gives you a rough idea of how many hits per second a server is capable of serving. You simply tell it what pages to grab, and how many “clients” it should run in parallel; it gives you back useful information about the average fetches per second and the average, minimum, and maximum response times. It’s no substitute for a solid profiler to dig into the hows and whys of your application’s performance, but it’s great at telling you when you’re “good enough” to launch.
Installing http_load on OS X
- Download from http://www.acme.com/software/http_load/
- Open terminal, cd to the directory where the archive is and unzip
$ tar xvzf http_load-12mar2006.tar.gz - Move to that directory
$ cd http_load-12mar2006 - Run
$ make - Run
$ sudo make install
How to check an MD5 hash on a file
MD5 is a one-way hash algorithm as defined by RFC1321 and can be used to help determine the integrity of a file by providing a 128 bit digital signature. This digital signature is like a fingerprint for a file, changing just one single byte in a file will result in a different MD5 hash.
MD5 hashes can be used to catalog files on a filesystem and then determine at a later date that the files have not been altered in any way, for example if someone broke into a system and modified system files.
They can also be used to ensure a file downloaded from a website is the same as expected. This can be especially important when downloading a file from a mirror site to ensure you are not installing a modified program which contains a trojan horse or some other nasty. By simply comparing the MD5 hash of the file you have downloaded from the mirror with that from the original website you can determine whether or not the file is exactly the same.
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Check / List Running Services
Q. How do I list all currently running services in CentOS / RHEL / Fedora Linux server ?
A. There are various ways and tools to find and list all running services under CentOS / RHEL / Fedora Linux systems.
service command – list running services
service --status-all
service --status-all | grep ntpd
service --status-all | less
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How to Change the Timezone in Linux
- Logged in as root, check which timezone your machine is currently using by executing `date`. You’ll see something like Mon Nov 9 13:49:01 EST 2009, PST in this case is the current timezone.
- Change to the directory /usr/share/zoneinfo here you will find a list of time zone regions. Choose the most appropriate region, if you live in Hong_Kong or the Singapore this directory is the “Asia” directory.
Install bandwidth monitor vnstat
vnStat is a network traffic monitor for Linux that keeps a log of daily network traffic for the selected interface(s). vnStat isn’t a packet sniffer. The traffic information is analyzed from the /proc -filesystem, so vnStat can be used without root permissions. However at least a 2.2.x kernel is required.
- Install vnStat
wget http://humdi.net/vnstat/vnstat-1.7.tar.gz
tar zxvf vnstat-1.7.tar.gz
cd vnstat-1.7
make
make install
Block IP Addresses With IPtables & APF
Have a user that keeps hammering your FTP or trying to login over and over and over again that you just want to ban and never see again? We’ll show a quick and dirty method to ban an IP address from the server.
We commonly receive questions like:
“I would like to ban that ip address to prevent the access to the server.
how can i ban that Ip address from the server?”
Simple !
Login to the server as root.
- If you are running iptables, you can enter:
iptables -A INPUT -s IP_ADDRESS -j DROP
Ex: Block IP 68.72.72.25
iptables -A INPUT -s 68.72.72.25 -j DROP
Tuning the Apache MaxClients parameter
One thing that can have a really drastic effect on a large site using Apache, is the value assigned to the MaxClients parameter.
This parameter defines how many simultaneous request can be served. Any connection request from browsers that come in after that will be queued.
Apache prefork, StartServers, MaxSpareServers and MinSpareServers
In the most common case, you will be using Apache in the prefork mode, meaning one process per connection, with a pool of processes pre-forked to standby for connections. The number of spare processes is defined by the values MaxSpareServers, MinSpareServers, while the number to start is defined by StartServers.
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Simple AJAX Example
This aims to be the easiest possible example demonstrating AJAX (Asynchronous JavaScript and XML).
AJAX is a technique rather than a technology: It describes how JavaScript can be used to pull data from the server using the XML HTTP Request object and then insert this data into the website using DOM. This is done asynchronously – that is, in the background, without having to refresh the whole page. The technology which AJAX is based on has already been available for a while, the combination is what makes it new.
You can try the examples online or download them and run them locally (except for the PHP script, that would require a webserver with PHP).
1. The DOM
The Document Object Model is the internal representation of your website. The DOM is accessible by JavaScript and provides a way to programmatically insert, remove and modify tags in your website (except that they are called elements or nodes instead of tags, because the DOM manipulates the data model in memory and not the representation as XML). This example shows how to set the content of the element with the id “foo” to “Hello, AJAX world!”: Read more…
Stop PHP nobody Spammers
PHP and Apache has a history of not being able to track which users are sending out mail through the PHP mail function from the nobody user causing leaks in formmail scripts and malicious users to spam from your server without you knowing who or where.
Watching your exim_mainlog doesn’t exactly help, you see th email going out but you can’t track from which user or script is sending it. This is a quick and dirty way to get around the nobody spam problem on your Linux server.
If you check out your PHP.ini file you’ll notice that your mail program is set to: /usr/sbin/sendmail and 99.99% of PHP scripts will just use the built in mail(); function for PHP – so everything will go through /usr/sbin/sendmail =)
Requirements:
We assume you’re using Apache 1.3x, PHP and Exim. This may work on other systems but we’re only tested it on a Cpanel/WHM Red Hat Enterprise system. Read more…
Rotating Banner in PHP
This is a snippet that will rotate a banner on a page. All you have to do is set $File and $Images to the paths to the images. It will just do the next image in $Images in order. It doesn’t rotate banners for seperate users, it just goes through. Before you use it, create the $Stat file and set the contents of it to 0 and your ready to go!
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