So If you’ve ever woke up in the morning and asked yourself…”Hmm, how can I make my system admin’s job harder to the point where they get mad and shut down my server?” Well, lucky for you I can answer that question. All you have to do is use the ‘dd‘ command to write a 120gb file to an 80gb hard drive. That’s a winner.

By ‘dd’ I’m not talking about my bra size, people. It’s sad, but we recently had an over-curious customer try to see what would happen if the hard drive filled up on his dedicated server. You know what happens when you flush a clogged toilet? Yea….

So here’s the command:

dd if=/dev/zero of=test bs=1024 count=125829120

This command will write a 120gb file directly to the disk. ‘of’ specifies the name of the output file, while ‘bs’ represents the size of a block and ‘count’ is how many blocks to create. Really, it’s a dangerous thing to do if you don’t know what you’re doing. Generally the only time I do this is when I’m testing large file support for servers and PHP.  Nevertheless, the sheer curiosity of ignorant users is enough for me to pull the power plug on a server.

Working with a webhosting company I get asked all the time — which programming language is better? It’s obvious that I’m more bias towards PHP, but there are other great languages out there that may be more suitable for certain people creating certain sites. I’ve decided to write a nutshell comparison on the most common languages, so you can decide for yourself.

PHP

My preferred language, PHP, is the most popular and widely-used dynamic programming language on the Internet. As a result, it’s increasingly become easy to learn (I have 4 brain cells and even I could do it) and can be run on virtually any operating system. It’s popularity has resulted in the availability of thundreds of contributions, modules, and addons for PHP to increase its functionality and integration with other software. It’s also free to download and easy to install (for most people), and is the most common in CMS’s and prebundled website software.

The major downside to PHP is that it’s so popular that security holes are being found all the time. Its very nature requires some configuration changes and restrictions in order to boost security.

Perl

Perl is one of the oldest and most successful languages to date. With thousands of modules that can be added, it can pretty much do anything. While it’s currently not as popular as PHP, it’s more efficient for server management in its double use as a shell scripting language. It’s also open-source and compatible for most all OS’s. The only real downside is that it’s not as quick and easy to learn, and even the simplest tasks can take more programming and lines of code to accomplish. Also, the camel logo is fugly.

ASP/VBScript

I’ll try to be nice about this one. Really, I’m not an ASP fan mainly because it’s proprietary to Windows and IIS. That being said, I’m sure you can figure how secure and reliable it is. It’s not as actively maintained by its developers (Microsoft) so major bugs have been known to linger for months — unacceptable for busy webmasters trying to manage professional websites. While ASP, .net, and VBScript (aka the ASP family) are all “free”, if you want any of the fancy addons or modules for them you’ll be owing Microsoft a nice little licensing fee. On a positive note, Chilisoft has made is possible to port ASP over to Linux, so it’s no longer 100% platform dependent.

JSP

Java Server Pages (developed by Sun) is more similar to the ASP framework, but targeted towards Java fanatics. Out of all the programming languages I’ve studied in school, JSP is probably my least favorite. Not only is it hard to learn, but there’s no such thing as simplicity with it. However, it’s very powerful software and is platform-independent, as long as you have a Java Environment for it to run in. Tomcat (an Apache Project) is the most common servlet container for JSP. But, Java takes up a lot of memory and JSP servers are very difficult to maintain and administer for non-experts.

Ruby

Ruby is one of the newer programming language to hit the web developer market, and it’s actually quite close in concept to PHP except that it’s 100% object-oriented, and very clean because you don’t need as much punctuation. It’s also very beginner-friendly, and is growing in popularity. The main disadvantage to Ruby is that it’s difficult to troubleshoot runtime errors because its reluctance to declare variables before their use. And being that it’s a newer language, there are definitely less resources available and not as many applications currently employing Ruby as a framework. However, it is cross-platform compatible, easy to install, and even easier to learn.

Python

I really don’t know a whole lot about Python other than that expert programmers claim that it’s such a strong language. I personally think it’s crap…my one shot at Python and I find out that it’s very whitespace/tab sensitive, so one extra space can ruin your program. Coming from PHP I don’t find that very appealing…I personally think it’s a mistake, and that its developers just call it a ‘programming guideline’ since they can’t figure out how to fix it. Really, there’s no huge benefit in using Python other than for your Google sitemaps, so all I’m going to say is steer clear.

HTML

I put this at the bottom of the list because I don’t really consider it a programming language, but it is the more predominate and widely used language that all the others revolve around. I do think it’s important that every programmer become an expert in HTML before going dynamic with their coding. While other languages rely on HTML for output, it’s very common for sites to be purely HTML and nothing else. However, HTML is a static language with no dynamic capabilities in itself whatsoever, so it’s somewhat boring on its own

Client-side

In a category all its own, there are several client-side languages that augment the others. Client side languages no require any server-side software to be installed, just a browser capable of interpreting them. CSS (Cascading Style Sheets) is a language primarily used in formatting and creating a uniform and repetitive style for use across multiple pages. JavaScript is a mini-java language used to create mild effects for a website, like popup windows and form validation. I also consider it to be very insecure, so it should be used sparingly. AJAX is a newer JavaScript framework that is more appealing to the eye and lets you create those special effects that you see on many web 2.0 sites…things like refresh-less page loading.

I don’t even know…I just came home one day and here they were:

If you’ve ever needed to move a ton of cPanel accounts from one server to another, you probably know the following:

1. The multiple account move feature in WHM fails miserably
2. It takes forever to do them one by one, esp. when you have other things to do

I figure the best way to mass-move accounts is by listing all the accounts in a file, then using a simple bash script to repetitively package all the accounts to they can be moved to another server.

First, you need to create a file (like users.txt) to list all the users you wish to move. If you’re only doing a few you can just go ahead and list the users in there manually, but if you’re doing like a whole server, you can get all the users in one file like so:

ls /var/cpanel/users > users.txt

You’ll then need to manually edit the users file and remove the ‘.’ and ”..’ entries, and any others that should not be included. The users.txt file should also be in a format like this:

user1
user2
user3
…

Next, you may want to set up an SSH key between servers so all the cpmove files and be transferred automatically. If you don’t know how to do this, here is a simple and straight-through tutorial.

Create a bash script called ‘cpbackup.sh’ with the following lines:

#! /bin/bash
for i in `cat users.txt`; do /scripts/pkgacct $i; done
scp -r /home/cpmove* root@server:/home
echo "Account backups done" > email.txt
mail -vv -s "Account backups done" your@emailaddress.com < email.txt

This will run cPanel backups up all the accounts listed in users.txt, scp them over to the new server, then email you when it’s done. Note that if you do not have SSH keys installed, you will have to manually type in the new server’s password when the script is ready to transfer the accounts over.

The on the new server you can use the same script and users.txt file, just change it around:

#! /bin/bash
for i in `cat users.txt`; do /scripts/restorepkg $i; done

This will restore all the user accounts that you copied over. From there, you’re all done!
One simple note: I’m not a shell programmer so I’m sure there are a lot better ways to accomplish this..if so, you can post them in a comment. The downside of using this method to move accounts is that all of the accounts are backed up in order so if you have a hundred some users, the backup files might be sitting on the server for hours until they are moved and restored, so you’ll want to make sure that your users are not making changes to their sites during the move process. Also, since the backup files are stored on the server it’s a good idea to figure out how much disk space you are going to need to avoid going over. You may be able to modify the script to do groups of 10-20 then delete the cpmove files if disk space is a concern.

I recently became pretty fond of Ubuntu when I installed it on my work computer after dealing with daily crashes of Windows XP Pro. I find it to be a lot easier to manage, though it sucks that some software is still not compatible with Unix and installing a wireless network card is about as hard as finding a 34D push-up bra at Victoria’s Secret. I mean, it’s a lingerie store…you’d think they’d have a bigger push-up bra. Maybe I want my boobs to peek out of my shirt every once in a while…or maybe I’ll decide to turn tricks someday and need a good “come get me” outfit. I also just realized that this is the third time today I went off on a tangent about boobs.

So anyways, out comes PCLinuxOS which is a new OS determined to be the bridge between Linux and Windows, targeted towards beginner Unix-ers who aren’t quite ready to kick Microsoft to the curb. It’s not quite the Gnome desktop, but rather a Windows Vista-inspired interface powered by a Linux core. I think it’s a good idea and will probably help the world see that Windows is officially the dead rat in the soup, by converting end users over to Linux. Best off, it’s completely free and can be downloaded here.
I don’t have any plans in the near future to use PCLinuxOS since I’ve become very content with Ubuntu, but If you’re a beginner to Unix you might want to give this one a look and let me know how it works.
Screenshots

Earlier I showed some examples of commands you can use to pull software versions into a simple PHP script. In the next example I’ll show how to do the distro and kernel versions. I’m sure that there’s a much simpler way to do this (i.e. a simple cat command on the /proc/version file), but I figured I’d use a more advanced example in the form of a function. I did the distro as a variable to show how easy this is:


<?php
function kernelinfo () {
$buf = exec( 'cat /proc/version');
if ( $buf == "ERROR" ) {
$result = "N.A.";
} else {
if (preg_match('/version (.*?) /', $buf, $ar_buf)) {
$result = $ar_buf[1];

if (preg_match('/SMP/', $buf)) {
$result .= ' (SMP)';
}
}
}
return $result;
}

$distro = exec('cat /etc/redhat-release');

$kernel = kernelinfo();

echo $distro;

echo "<html><br></html>";

echo $kernel;

?>


This will show a result of the following, obviously various depending on your platform:

CentOS release 4.5 (Final)
2.6.9-023stab033.9-enterprise (SMP)

Keep in mind that this script (as the last) requires the ability to pass shell commands through PHP. So, you would need to be able to the exec function, or replace it with system, passthru, escapeshellcmd, or shell_exec if those are allowed in your php.ini configuration. Also, if you run PHP as an Apache module, this will not work if you have open_basedir protection enabled.

I’ve been working on this application for work that does some simple server reporting, part of which involves displaying the versions of major software running on the machines. The importance of this to me personally is that since we have over 30 shared servers hosting multiple customers, we are continually moving websites between servers. Some of our older generation servers are still running MySQL 4.0 and PHP 4.3, so I need to be aware of this to make sure that customers are being moved to servers with compatible versions. It’s also good in tracking and planning upgrades.

I find it best to use the exec() function since it’s not blocked by most hosts. However, if you are on a shared host it’s very likely that certain PHP functions are disallowed in the php.ini. In that case you may be able to subsitute exec with system, passthru, escapeshellcmd, or shell_exec…unless those are blocked too. Then I guess you’re out of luck.

Start by creating some variables to store ordinary shell commands. If you wanted to find the php version from command line, you would usually type:

php -v

This will give a huge chunk of crap that you really don’t need if you’re making a simple version display script. In this case, you can use grep, awk, sed, and cut to trim down the output into a one-liner:

php -v |grep built |awk {‘print $2′}

The awk command prints out columns, so in the above example I’m printing out the second column of the line that contains the word ‘built’. Once the desired output is figured out, you simply assign it to a variable passed through exec() or a similar function:

$phpver = exec("php -v |grep built |awk {'print $2'}");

Then you can call the variable $phpver anywhere in your script:

echo "PHP Version: $phpver";

You can probably go through and figure out the commands to show other software versions on your server. In my script I’m showing the perl, php, mysql, apache, python, cpanel, and ruby versions. Here are the commands I used:

<?php

$perlver = exec("perl -v |grep linux |awk {'print $4'}|sed -e 's/v//'");
$phpver = exec("php -v |grep built |awk {'print $2'}");
$mysqlver = exec("mysql -V |awk {'print $5'} | sed -e 's/,//'");
$apachever = exec("apachectl -v |grep version |awk {'print $3 $4'}|sed -e 's/Apache\///'");
$pythonver = exec("python -V 2>&1 | sed -e 's/Python //'");
$cpanelver = exec("cat /usr/local/cpanel/version");
$rubyver = exec("ruby -v |awk {'print $2'}"); ?>

Then I just echoed out all the variables to display my version numbers:

See here .