How To Heaven

How to fix vsftpd error “500 OOPS: cannot change directory:/some/directory”

2012-08-21T04:26:00.002-07:00

that error is generate for Selinux plz do the following actions:

[root@sun02 vsftpd]# getenforce
Enforcing
[root@sun02 vsftpd]# getsebool -a | grep ftp
allow_ftpd_anon_write –> off
allow_ftpd_full_access –> off
allow_ftpd_use_cifs –> off
allow_ftpd_use_nfs –> off
allow_tftp_anon_write –> off
ftp_home_dir –> on (change that to on in ur case this option is off)
ftpd_disable_trans –> off
ftpd_is_daemon –> on
httpd_enable_ftp_server –> off
tftpd_disable_trans –> off
[root@sun02 vsftpd]# setsebool -P ftp_home_dir on

This is all that u want to need.

Good Luck!

how to create a custom Pinterest “Pin It” button for your website

2012-07-14T13:48:00.001-07:00

Here is the Javascript code I use to create a Pin It button for a web page using a custom graphic:

<div>
<a href="javascript:void((function(){var%20e=document.createElement('script'); e.setAttribute('type','text/javascript'); e.setAttribute('charset','UTF-8'); e.setAttribute('src','http://assets.pinterest.com/js/pinmarklet.js?r='+Math.random()*99999999);document.body.appendChild(e)})());"> <img src="images/pinit.jpg" alt="Pin It" /></a> </div>

You will want to change the path to the image in the code above so that it points to the graphic that you want to use for the Pin It button. You could also substitute text for the graphic if you prefer.

ho to Set static front page and blog page programmatically in WordPress

2012-07-08T07:26:00.000-07:00

You want to make sure the About and Blog pages exist, so create them before if necessary, see wp_insert_post()

<?php

// Use a static front page
$about = get_page_by_title( 'About' );
update_option( 'page_on_front', $about->ID );
update_option( 'show_on_front', 'page' );

// Set the blog page
$blog   = get_page_by_title( 'Blog' );
update_option( 'page_for_posts', $blog->ID );

// Switch to our theme
//switch_theme( 'Template', 'stylesheet' );
?>

How to Force a WordPress plugin to be loaded before all other plugins

2012-07-06T07:17:00.003-07:00

When you activate a plugin via the WordPress admin panel it calls the action hook “activated_plugin“, which updates the “active_plugins” site option stored in the database to determine which plugins your site should load.
The option value is a serialized array of the active plugins saved in alphabetical order according to the plugin directory and file name, for example:

Array
(
 [0] => akismet/akismet.php
 [1] => example-plugin/index.php
)

You can however alter the order of the plugins in the array, which will in turn set the order in which the plugins are loaded by WordPress.
The first step towards adjusting the order is to add the following action to your plugin file, which is most likely to be /my-plugin/index.php or /my-plugin/my-plugin.php.

add_action( 'activated_plugin', 'my_plugin_load_first' );

Next you need to include the functionality to perform the actual re-ordering. The following function will fetch the existing list, check that your plugin is in the array and if so remove then append it to the beginning, before finally saving the altered list to the database.

function my_plugin_load_first()
{
 $path = str_replace( WP_PLUGIN_DIR . '/', '', __FILE__ );
 if ( $plugins = get_option( 'active_plugins' ) ) {
  if ( $key = array_search( $path, $plugins ) ) {
   array_splice( $plugins, $key, 1 );
   array_unshift( $plugins, $path );
   update_option( 'active_plugins', $plugins );
  }
 }
}

It should not be necessary for you to adjust anything specified here other than modifying the name of the function used to suit the namespace used by your plugin.
One final thing to consider is only adding this action when the dashboard or administration panels are being displayed, by making use of the is_admin() conditional tag.
Please note that modifying this option is not something I recommend people do unless absolutely necessary, and it my situation it proved to be very useful.

How to load the template you want with template_redirect - Wordpress

2012-07-04T12:11:00.000-07:00

If you’re a web developer and you are using WordPress to create a website rather than a blog, I’m pretty sure you would try to achieve some of the following:

use a different layout for a certain category (and maybe all it’s subcategories)
use a different layout for a certain post
use a different layout for a certain post inside a certain category
load a different page for a certain non-WordPress-URL

If I guessed, then this tutorial is for you.

template_redirect – where all begins

The drawing bellow illustrates how template_redirect works. Basically, you use it to intervene just before WordPress decides which template to use, and then override it with what you want.

The simplest way to show how template_redirect works would be to tell WordPress that, no matter which page is requested, just display “Testing template_redirect” on a blank page.
The code is below. I recommend you put it in functions.php file of your theme:

function my_template() {

     echo "Testing template_redirect";

     exit;

}

add_action('template_redirect', 'my_template');

add_action is a function that allows you to hook to certain moments in the WordPress loading process and provide custom functionality. template_redirect is one of the many functionalities you can alter.
As a result of the add_action call, WordPress will execute my_template function every time a page is requested in order to find out which template should it load.
As I said above, this example just prints that text and does nothing afterward (because of the exit keyword). If exit would not be present, the text would have been printed, and WordPress would have continued with it’s default logic.

So, what can we really do inside template_redirect?

Because I don’t like theory either, I will begin with some simples examples and explanations.

Use a different template for a certain category (example “fun”)

function my_template() {

    if (is_category() && get_query_var('cat') == get_cat_id('fun')) {

        include (TEMPLATEPATH . '/category-fun.php');

        exit;

    }

}

add_action('template_redirect', 'my_template');

The first thing we check is whether we find ourselves in a category. is_category() tells me if I am currently trying to access a category page. This first condition is useful, because we wouldn’t want to apply this rule to a post, to a page or the front page.
The next condition (get_query_var(‘cat’) == get_cat_id(‘fun’)) checks whether we are trying to access the “fun” category of our blog. get_query_var gets the numeric id of the category we are currently accessing. get_cat_id gets the id for the given category name. We could also do get_query_var(‘cat’) == 7 (assuming that “fun” has the id 7, but it is not recommended to leave numbers in your code, as later you won’t have any idea what “7″ represents)
If both conditions are true, that means we are accessing the “fun” category and we load a different template for it. In this case, we include the file “category-fun.php” and then exit. As I said above, we exit because we loaded the template and we have to tell WordPress to stop executing the default logic.
If one or both conditions are false, then nothing happens, and WordPress continues to process it’s default logic, thus loading the default category page.

Use a different template for a certain category and all it’s subcategories (example “fun”)

Suppose now that our “fun” category has more subcategories, such as “jokes”, “cats”, “epic fails”, “shows”. If you want all these categories (including their parent – fun) to have the same template, there are two options:
- either you add more conditions to the function in the previous example (which is really not a good idea, as for any new subcategories you would also have to add new conditions)
- either you use the code below that explicitly states that both fun and it’s subcategories (that may change in time) will be loaded using the given template (this is the good solution)

function my_template() {

    if (is_category() &&

            (get_query_var('cat') == get_cat_id('fun') ||

            cat_is_ancestor_of(get_cat_id('fun'), get_query_var('cat')))) {

        include (TEMPLATEPATH . '/category-fun.php');

        exit;

    }

}

add_action('template_redirect', 'my_template');

This example adds a new condition referring to the category ancestor. So basically now, all it does is check:

whether it is the “fun” category itself OR
whether it is a category that is a children of “fun”

Use a different layout for a certain post

function my_template() {

    if (is_single()) {

        global $post;

        if ($post->ID == 10) {

            include (TEMPLATEPATH . '/post-with-id-10.php');

            exit;

        }

        if ($post->post_name == 'hello-world') {

            include (TEMPLATEPATH . '/post-with-permalink-hello-world.php');

            exit;

        }

    }

}

add_action('template_redirect', 'my_template');

The example below shows that you can check for any property of the post in order to take a decision about which template to load.
is_single() returns true if a single post is being accessed.

Use a different layout for a certain post inside a certain category

function my_template() {

    if (is_single()) {

        global $post;

        $current_post_categories = wp_get_post_categories($post->ID);

        if (in_array(get_cat_id('fun'),$current_post_categories)) {

            include (TEMPLATEPATH . '/post-in-fun.php');

            exit;

        }

    }

}

add_action('template_redirect', 'my_template');

The first thing we do is to get the list of categories in which the current post belongs and then see if “fun” is one of them. If yes, that means the post is in the “fun” category and we load it’s template.

Load a different page for a certain non-WordPress-URL

This is a bit tricky, because if you want to have a custom link structure for some sections of your website, if they do not look like what WordPress knows, it will throw you a nice 404 not found response and will mess up both your SEO and your page (on some browsers like Internet Explorer, if it receives a 404, it displays their default 404 page). That’s why first we have define a function like this:

function include_wordpress_template($t) {

    global $wp_query;

    if ($wp_query->is_404) {

        $wp_query->is_404 = false;

        $wp_query->is_archive = true;

    }

    header("HTTP/1.1 200 OK");

    include($t);

}

What this function does is it removes the 404 flag for WordPress, it sends the 200 OK header and then includes the requested template

function my_template() {

    if ($_SERVER['REQUEST_URI'] == '/high-scores') {

        include_wordpress_template(TEMPLATEPATH . '/high-scores.php');

    }

}

add_action('template_redirect', 'my_template');

What this function does is that if someone enters on /high-scores, it justs loads a certain template, without letting wordpress deciding whether it is a post or a page. It is extremly useful for embedding extra-functionality based on a custom link structure. It’s like building a whole new attached to the structure of WordPress, but without needing to map it to the WordPress default entities such as “posts”, “pages”, “categories”, “tags”, etc.

Where to go from here

This tutorial presented you some basic examples of how you can load custom templates depending on some given conditions. As you can see, the possiblities are limitless and this is where you must begin to make a simple WordPress blog become a complex website.
I recommend reading the WordPress Codex to find out what other cool functions you can use.
Some quick links for that are: Conditional Tags, Query posts, Function reference

How to add jQuery Thickbox on Ajax Generated Pages

2012-06-27T13:18:00.001-07:00

The jQuery thickbox plugin is fantastic. All you have to do is include the js file, and give the elements that require a jQuery thickbox, a class of thickbox. Like below;

<a class="thickbox" href="thickboxexample.php?height=600&width=600">jQuery Thickbox Example</a>

The thickbox plugin then automically!! attaches its events to those elements. For ease of use this is great, but it has its limitations, because the events are attached on page load.
What happens when you want to attach a thickbox to an element that is generated via an ajax call?
Well you’re gonna kick yourself! You simply need to re-call the the thickbox initialise function within your ajax call, just like the example below:

$.ajax({
    type:       "GET",
    url:        "/ajax-content.php",
    cache:      false,
    data:       "f=foo&b=bar",
    loading:    $('.loading').html(""),
    success:    function(html) {
                    $("#ajaxContent").html(html);
                    //re-attach thickbox
                    tb_init('a.thickbox, area.thickbox, input.thickbox');
                }
});

I am assuming that you already know how to make an ajax call using jQuery, so I won’t explain the above code, except for the fact that a call is made to tb_init() after the ajax response. This is the thickbox initialise function which attaches its events to your selected elements.

How To Use PHP to Force a File Download

2012-06-20T08:12:00.001-07:00

PHP allows you to change the HTTP headers of files that you're writing, so that you can force a file to be downloaded that normally the browser would load in the same window. This is perfect for files like PDFs, document files, images, and video that you want your customers to download rather than read online.

Here's How:

Upload the file you want to make available for download to your Web server. For example,
huge_document.pdf
Edit a new PHP file - I recommend naming it the same name as your downloaded file, only with the extension .php. For example:
huge_document.php
Open the PHP block:
<?php
On the next line, set the HTTP header:
header('Content-disposition: attachment; filename=huge_document.pdf');
Then set the MIME-type of the file:
header('Content-type: application/pdf');
Point to the file you want to download:
readfile('huge_document.pdf');
Then close the PHP block and save the file:
?>[/blockquote>
Your PHP file should look like this:
<?php
header('Content-disposition: attachment; filename=huge_document.pdf');
header('Content-type: application/pdf');
readfile('huge_document.pdf');
?>
Link to your PHP file as a download link. For example:
<a href="huge_document.php">Download my huge document (PDF)</a>

Tips:

There should be no spaces or carriage returns anywhere in the file. Blank lines will cause PHP to default to text/html and your file won't download.

What You Need

The file to be downloaded
The MIME type of the file

How to send email from the Linux command line

2012-06-20T04:01:00.000-07:00

The Linux command line can be very powerful once you know how to use it. You can parse data, monitor processes, and do a lot of other useful and cool things using it. There often comes a need to generate a report and mail it out. It could be as simple a requirement as a notification that the day’s backup went through fine, or did not. I’ll help you get started with sending mails from the Linux command line and in shell scripts. We will also cover sending attachments from the command line. We will begin with the “mail” command.

MAIL

First run a quick test to make sure the “sendmail” application is installed and working correctly. Execute the following command, replacing “you@youremailid.com” with your e-mail address.
# mail -s “Hello world” you@youremailid.com
Hit the return key and you will come to a new line. Enter the text “This is a test from my server”. Follow up the text by hitting the return key again. Then hit the key combination of Control+D to continue. The command prompt will ask you if you want to mark a copy of the mail to any other address, hit Control+D again. Check your mailbox. This command will send out a mail to the email id mentioned with the subject, “Hello world”.
To add content to the body of the mail while running the command you can use the following options. If you want to add text on your own:
# echo “This will go into the body of the mail.” | mail -s “Hello world” you@youremailid.com
And if you want mail to read the content from a file:
# mail -s “Hello world” you@youremailid.com < /home/calvin/application.log
Some other useful options in the mail command are:
-s subject (The subject of the mail)
-c email-address (Mark a copy to this “email-address”, or CC)
-b email-address (Mark a blind carbon copy to this “email-address”, or BCC)
Here’s how you might use these options:
# echo “Welcome to the world of Calvin n Hobbes” | mail -s “Hello world” calvin@cnh.com -c hobbes@cnh.com -b susie.derkins@cnh.com

MUTT

One of major drawbacks of using the mail command is that it does not support the sending of attachments. mutt, on the other hand, does support it. I’ve found this feature particularly useful for scripts that generate non-textual reports or backups which are relatively small in size which I’d like to backup elsewhere. Of course, mutt allows you to do a lot more than just send attachments. It is a much more complete command line mail client than the “mail” command. Right now we’ll just explore the basic stuff we might need often. Here’s how you would attach a file to a mail:
# echo “Sending an attachment.” | mutt -a backup.zip -s “attachment” calvin@cnh.com
This command will send a mail to calvin@cnh.com with the subject (-s) “attachment”, the body text “Sending an attachment.”, containing the attachment (-a) backup.zip. Like with the mail command you can use the “-c” option to mark a copy to another mail id.

SENDING MAIL FROM A SHELL SCRIPT

Now, with the basics covered you can send mails from your shell scripts. Here’s a simple shell script that gives you a reading of the usage of space on your partitions and mails the data to you.

#!/bin/bash
df -h | mail -s “disk space report” calvin@cnh.com

Save these lines in a file on your Linux server and run it. You should receive a mail containing the results of the command. If, however, you need to send more data than just this you will need to write the data to a text file and enter it into the mail body while composing the mail. Here’s and example of a shell script that gets the disk usage as well as the memory usage, writes the data into a temporary file, and then enters it all into the body of the mail being sent out:

#!/bin/bash
df -h > /tmp/mail_report.log
free -m >> /tmp/mail_report.log
mail -s “disk and RAM report” calvin@cnh.com < /tmp/mail_report.log

Now here’s a more complicated problem. You have to take a backup of a few files and mail then out. First the directory to be mailed out is archived. Then it is sent as an email attachment using mutt. Here’s a script to do just that:

#!/bin/bash
tar -zcf /tmp/backup.tar.gz /home/calvin/files
echo | mutt -a /tmp/backup.tar.gz -s “daily backup of data” calvin@cnh.com

The echo at the start of the last line adds a blank into the body of the mail being set out.
This should get you started with sending mails form the Linux command line and from shell scripts. Read up the “man page” for both mail and mutt for more options.

how to fix Yum thread.error: can’t start new thread

2012-05-17T06:06:00.002-07:00

If you get this error (thread.error: can’t start new thread) when you are trying to update your CentOS (I got this error when I tried to install PHP), you have a two step solution to overcome this issue. This is not very common issue, and its about the memory resource problem with the VPS which is caused by Yum’s fastestmirror plugin. Here is the solution;

Stop the mysql server.
Start Yum again after disabling Yum’s fastestmirror plugin like the code below;

yum --disableplugin=fastestmirror update

You should now update your CentOS.

How to Install Apache 2.4.2 from Source on CentOS 6.2 with SSL

2012-05-10T14:36:00.001-07:00

Make sure you have gcc and openssl-devel installed.

# yum install gcc
# yum install openssl-devel

You also need “Apache Portable Runtime Library” APR to install Apache from source.
You’ll already have “apr” and “apr-util” package installed. Install the apr-devel and apr-util-devel packages.

# yum install apr-devel
# yum install apr-util-devel

Note: In our case (because of the version compatibility issues), we’ll be downloading these and installing it manually later. But, let us go with the flow for now and see what happens when you try to do it this way.

Download Apache

Download Apache from httpd.apache.org. The current stable release is 2.4.2.
Once you get the direct URL to download the latest stable version of Apache, use wget as shown below to download it directly to you server.

cd /usr/src
wget http://mirror.nyi.net/apache//httpd/httpd-2.4.2.tar.gz
tar xvfz httpd-2.4.2.tar.gz

Install Apache with SSL/TLS

View all available Apache installation and configuration options as shown below.

cd httpd-2.4.2
./configure --help

To install an Apache module, you would typically say –enable-{module-name}. For example, to install SSL with Apache, it is –enable-ssl. To install ldap module, it is –enable-ldap.
To uninstall any default module that comes with Apache, you would typically say –disable-{module-name}. For example, to disable basic authentication in Apache, it is –disable-auth-basic
In this example, we will install Apache with all default modules, with addition of –enable-ssl (to install mod_ssl for SSL support), and –enable-so, which helps to load modules in Apache during run-time via the Dynamic Shared Object (DSO) mechanism, rather than requiring a recompilation.

./configure --enable-ssl --enable-so
make
make install

Note: By default the above installs Apache under /usr/local/apache2. If you like to change this location, use –prefix option in the ./configure.

Fixing APR Utility Error Messages

You might’ve not faced this problem while installing older version of Apache as we discussed a while back.
When you execute the “make”, you might get “rotatelogs.c:(.text+0x5ed): undefined reference to `apr_file_link’” error message if you are doing this on CentOS 6.2 as shown below.

# make
rotatelogs.c:298: warning: implicit declaration of function âapr_file_linkâ
/usr/lib64/apr-1/build/libtool --silent --mode=link gcc -std=gnu99 -pthread
-o rotatelogs  rotatelogs.lo /usr/lib64/libaprutil-1.la -ldb-4.7 -lexpat -ldb-4.7 /usr/lib64/libapr-1.la -lpthread
rotatelogs.o: In function `post_rotate':
rotatelogs.c:(.text+0x5ed): undefined reference to `apr_file_link'
collect2: ld returned 1 exit status
make[2]: *** [rotatelogs] Error 1
make[2]: Leaving directory `/usr/src/httpd-2.4.2/support'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/usr/src/httpd-2.4.2/support'
make: *** [all-recursive] Error 1

This is because on CentOS 6, the latest APR version available through yum installation is 1.3.9 as shown below.

# rpm -qa apr*
apr-1.3.9-3.el6_1.2.x86_64
apr-util-1.3.9-3.el6_0.1.x86_64

However, Apache 2.4.2 needs the latest version of APR (which is currently 1.4.6).
So, go to APR download page and download both apr and apr-util.

cd /usr/src
wget http://mirror.atlanticmetro.net/apache//apr/apr-1.4.6.tar.gz
wget http://mirror.atlanticmetro.net/apache//apr/apr-util-1.4.1.tar.gz
tar xvfz apr-1.4.6.tar.gz
tar xvfz apr-util-1.4.1.tar.gz

Now, you should place this new version of apr and apr-util directories (without the version name in the directory) under “srclib” directory located under the httpd-2.4.2 directory that was created when you uncompressed the downloaded apache software.
In my example, I downloaded the httpd-2.4.2.tar.gz and uncompressed it under /usr/src. So, I need to place the latest apr and apr-util under this directory.

mv apr-1.4.6 /usr/src/httpd-2.4.2/srclib/apr
mv apr-util-1.4.1 /usr/src/httpd-2.4.2/srclib/apr-util

After this is done, we need to configure and make it again. If you execute the ./configure –help, you’ll see the following options that are related to APR

# cd /usr/src/httpd-2.4.2
# ./configure --help
  --with-included-apr     Use bundled copies of APR/APR-Util
  --with-apr=PATH         prefix for installed APR or the full path to apr-config
  --with-apr-util=PATH    prefix for installed APU or the full path to apu-config

If you decide to install the apr-1.4.6 and apr-util-1.4.1 on your system, you need to use “–with-apr” and “–with-apr-util” and provide the path where you installed these utility.
In this example, we didn’t do that. i.e We didn’t install the apr and apr-util that we downloaded. Instead we placed them under the httpd-2.4.2/srclib/apr-util. So, we should use “–with-included-apr” in the ./configure which will use these apr and apr-util only for the apache compilation and installation.
So, let us re-do the ./configure (using –with-included-apr), make and make install as shown below.

./configure --enable-ssl --enable-so --with-included-apr
make
make install

Now, make will not give “rotatelogs.c:(.text+0x5ed): undefined reference to `apr_file_link” error message anymore.

Enable SSL in httpd.conf

Apache configuration file httpd.conf is located under /usr/local/apache2/conf.
Uncomment the httpd-ssl.conf Include line and the LoadModule ssl_module line in the /usr/local/apache2/conf/httpd.conf file.

# vi /usr/local/apache2/conf/httpd.conf
LoadModule ssl_module modules/mod_ssl.so
Include conf/extra/httpd-ssl.conf

View the httpd-ssl.conf to review all the default SSL configurations. For most cases, you don’t need to modify anything in this file.

# vi /usr/local/apache2/conf/extra/httpd-ssl.conf

The SSL certificate and key are required before we start the Apache. The server.crt and server.key file mentioned in the httpd-ssl.conf needs to be created before we move forward.

# cd /usr/local/apache2/conf/extra
# egrep 'server.crt|server.key' httpd-ssl.conf
SSLCertificateFile "/usr/local/apache2/conf/server.crt"
SSLCertificateKeyFile "/usr/local/apache2/conf/server.key"

Create server.crt and server.key file

First, Generate the server.key using openssl.

# cd /usr/src
# openssl genrsa -des3 -out server.key 1024

The above command will ask for the password. Make sure to remember this password. You need this while starting your Apache later.
Next, generate a certificate request file (server.csr) using the above server.key file.

# openssl req -new -key server.key -out server.csr

Finally, generate a self signed ssl certificate (server.crt) using the above server.key and server.csr file.

# openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt

After you’ve done with the above steps, you’ll see the following three files under /usr/src

# ls server*
server.crt  server.csr  server.key

Copy the server.key and server.crt file to appropriate Apache configuration directory location.

cp server.key /usr/local/apache2/conf/
cp server.crt /usr/local/apache2/conf/

Start the Apache

If you are getting the below error message, make sure to uncomment the line shown below in httpd.conf

# /usr/local/apache2/bin/apachectl start
AH00526: Syntax error on line 51 of /usr/local/apache2/conf/extra/httpd-ssl.conf:
Invalid command 'SSLCipherSuite', perhaps misspelled or defined by a module not included in the server configuration

# vi /usr/local/apache2/conf/httpd.conf
LoadModule ssl_module modules/mod_ssl.so

If you are getting the below error message, make sure to uncomment the line shown below in httpd.conf

# /usr/local/apache2/bin/apachectl start
AH00526: Syntax error on line 76 of /usr/local/apache2/conf/extra/httpd-ssl.conf:
SSLSessionCache: 'shmcb' session cache not supported (known names: ). Maybe you need to load the appropriate socache module (mod_socache_shmcb?).

# vi /usr/local/apache2/conf/httpd.conf
LoadModule socache_shmcb_module modules/mod_socache_shmcb.so

Finally, this will prompt you to enter the password for your private key before starting up the apache.

# /usr/local/apache2/bin/apachectl start
Apache/2.4.2 mod_ssl (Pass Phrase Dialog)
Some of your private key files are encrypted for security reasons.
In order to read them you have to provide the pass phrases.

Server www.example.com:443 (RSA)
Enter pass phrase:

OK: Pass Phrase Dialog successful.

Verify that the Apache httpd process is running in the background

# ps -ef | grep http
root   29529     1  0 13:08 ?     00:00:00 /usr/local/apache2/bin/httpd -k start
daemon 29530 29529  0 13:08 ?     00:00:00 /usr/local/apache2/bin/httpd -k start
daemon 29531 29529  0 13:08 ?     00:00:00 /usr/local/apache2/bin/httpd -k start
daemon 29532 29529  0 13:08 ?     00:00:00 /usr/local/apache2/bin/httpd -k start
root   29616 18260  0 13:09 pts/0 00:00:00 grep http

To stop the apache use apachectl stop.

# /usr/local/apache2/bin/apachectl stop

Use httpd -l to view all the modules that are compiled inside the Apache httpd daemon.

# /usr/local/apache2/bin/httpd -l
Compiled in modules:
  core.c
  mod_so.c
  http_core.c
  event.c

By default Apache SSL runs on 443 port. Open a web browser and verify that you can access your Apache using https://{your-ip-address}

How Traceroute Works

2012-05-10T14:33:00.001-07:00

There are scenarios in which one would like to know the route which a connection follows. By route here we mean the IP addresses of all the forwarding entities (like routers in between).
Although there is no guarantee that the route will remain same for all the packets of a connection but usually it is same. This route related information can be very handy while debugging network related issues.

traceroute utility prints out complete route to a particular destination. In this article we will discuss how traceroute works and will see some practical examples.

How Traceroute Works?

Before beginning with examples, lets understand the concept on which traceroute works.
Traceroute utility uses the TTL field in the IP header to achieve its operation. For users who are new to TTL field, this field describes how much hops a particular packet will take while traveling on network.
So, this effectively outlines the lifetime of the packet on network. This field is usually set to 32 or 64. Each time the packet is held on an intermediate router, it decreases the TTL value by 1. When a router finds the TTL value of 1 in a received packet then that packet is not forwarded but instead discarded.
After discarding the packet, router sends an ICMP error message of “Time exceeded” back to the source from where packet generated. The ICMP packet that is sent back contains the IP address of the router.
So now it can be easily understood that traceroute operates by sending packets with TTL value starting from 1 and then incrementing by one each time. Each time a router receives the packet, it checks the TTL field, if TTL field is 1 then it discards the packet and sends the ICMP error packet containing its IP address and this is what traceroute requires. So traceroute incrementally fetches the IP of all the routers between the source and the destination.
You should also understand the IP header fields that we discussed a while back.

Traceroute Examples

1. How to run traceroute?

$ traceroute <server-name>

The server-name above is the destination name or IP address. For example, traceroute is used to find the network path from my machine to google.com :

$ traceroute google.com
traceroute to google.com (74.125.236.132), 30 hops max, 60 byte packets
1  220.224.141.129 (220.224.141.129)  89.174 ms  89.094 ms  89.054 ms
2  115.255.239.65 (115.255.239.65)  109.037 ms  108.994 ms  108.963 ms
3  124.124.251.245 (124.124.251.245)  108.937 ms  121.322 ms  121.300 ms
4  * 115.255.239.45 (115.255.239.45)  113.754 ms  113.692 ms
5  72.14.212.118 (72.14.212.118)  123.585 ms  123.558 ms  123.527 ms
6  72.14.232.202 (72.14.232.202)  123.499 ms  123.475 ms  143.523 ms
7  216.239.48.179 (216.239.48.179)  143.503 ms  95.106 ms  95.026 ms
8  bom03s02-in-f4.1e100.net (74.125.236.132)  94.980 ms  104.989 ms  104.954 ms

Each lines gives the details of interaction with each router encountered. So we see that traceroute not only gives the IP addresses of the intermediate routers but also three round trip times for that particular router as for each router the traceroute commands fires three packets.

The ‘*’ field in output

There are times when one could encounter an ‘*’ in the output rather than a value. This depicts that the required field could not be fetched. The reason can be anything from reverse DNS lookup failure to packets not hitting the target router to packets getting lost on their way back. So we see that the reason could be many but for all these type of cases the traceroute utility provides an * in the output.

2. Disable IP address and host name mapping

Traceroute provides and option through which the mapping of IP addresses with host name (that traceroute tries) is disabled. The option for doing this is ‘-n’ . Following example illustrates it :

$ traceroute google.com -n
traceroute to google.com (173.194.36.7), 30 hops max, 60 byte packets
1  220.224.141.129  109.352 ms  109.280 ms  109.248 ms
2  115.255.239.65  131.633 ms  131.598 ms  131.573 ms
3  124.124.251.245  131.554 ms  131.529 ms  131.502 ms
4  115.255.239.45  131.478 ms  131.464 ms  199.741 ms
5  72.14.212.118  199.674 ms  199.637 ms  199.603 ms
6  209.85.241.52  199.578 ms  199.549 ms  209.838 ms
7  209.85.241.187  199.488 ms  177.264 ms  177.196 ms
8  173.194.36.7  177.159 ms  187.463 ms  187.434 ms

So we see that no host name is displayed in the output.

3. Configure Response Wait Time

The time for which traceroute utility waits after issuing a probe can also be configured. This can be done through ‘-w’ option that it provides. The -w option expects a value which the utility will take as the response time to wait for. In this example, the wait time is 0.1 seconds and the traceroute utility was unable to wait for any response and it printed all the *’s.

$ traceroute google.com -w 0.1
traceroute to google.com (74.125.236.101), 30 hops max, 60 byte packets
1  * * *
2  * * *
3  * * *
..
26  * * *
27  * * *
28  * * *
29  * * *
30  * * *

So we see that traceroute tried 30 attempts (the max hop attempts) and then gave up as no ICMP packet was received in 0.1 seconds.

4. Configure Number of Queries per Hop

As already explained earlier, the traceroute utility sends 3 packets per hop to provide 3 round trip times. This default value of 3 is configurable using the option ‘-q’. This option expects an integer which it sets as new value of number of probes per hop.

$ traceroute google.com -q 5
traceroute to google.com (173.194.36.46), 30 hops max, 60 byte packets
1  220.224.141.129 (220.224.141.129)  91.579 ms  91.497 ms  91.458 ms  91.422 ms  91.385 ms
2  115.255.239.65 (115.255.239.65)  91.356 ms  91.325 ms  98.868 ms  98.848 ms  98.829 ms
3  124.124.251.245 (124.124.251.245)  94.581 ms  107.083 ms  107.044 ms  107.017 ms  106.981 ms
4  115.255.239.45 (115.255.239.45)  106.948 ms  106.918 ms  144.432 ms  144.412 ms  144.392 ms
5  72.14.212.118 (72.14.212.118)  115.565 ms  115.485 ms  115.446 ms  115.408 ms  115.381 ms
6  72.14.232.202 (72.14.232.202)  115.351 ms  87.232 ms  117.157 ms  117.123 ms  117.049 ms
7  209.85.241.189 (209.85.241.189)  126.998 ms  126.973 ms  126.950 ms  126.929 ms  126.912 ms
8  bom04s02-in-f14.1e100.net (173.194.36.46)  126.889 ms  95.526 ms  95.450 ms  95.418 ms  105.392 ms

So we see that after configuring the number of probes to 5, the output started showing five round trip times per hop.

5. Configure the TTL value to start with

Traceroute utility is flexible enough to accept the TTL value that the user wants to start the utility with. By default its value is 1 which means it starts off with the first router in the path but using the ‘-f’ option (which expects the new value of TTL) a new value of the TTL field can be set. For example, I tried a normal traceroute operation and then tried a traceroute with a different TTL value.

$ traceroute google.com
traceroute to google.com (74.125.236.132), 30 hops max, 60 byte packets
1  220.224.141.129 (220.224.141.129)  89.181 ms  101.540 ms  101.503 ms
2  115.255.239.65 (115.255.239.65)  101.468 ms  101.431 ms  101.324 ms
3  124.124.251.245 (124.124.251.245)  121.373 ms  121.350 ms  158.694 ms
4  115.255.239.45 (115.255.239.45)  101.223 ms  141.135 ms  123.932 ms
5  72.14.212.118 (72.14.212.118)  123.867 ms  123.832 ms  123.802 ms
6  72.14.232.202 (72.14.232.202)  123.773 ms  123.742 ms  587.812 ms
7  216.239.48.179 (216.239.48.179)  587.723 ms  587.681 ms  587.642 ms
8  bom03s02-in-f4.1e100.net (74.125.236.132)  577.548 ms  577.524 ms  587.512 ms

$ traceroute google.com -f 8
traceroute to google.com (74.125.236.129), 30 hops max, 60 byte packets
8  bom03s02-in-f1.1e100.net (74.125.236.129)  96.961 ms  96.886 ms  96.849 ms

So we see that after using the -f option with value 8, only the last (8th) line from the previous output was shown.

How to add cakePHP auto-complete to netbeans

2012-05-03T05:25:00.003-07:00

NetBeans is a very powerful development environment for many languages including PHP. With the release of its latest version, NetBeans announced full support for symfony PHP framework. NetBeans can also support many other PHP frameworks and libraries although it is not officially supported by NetBeans. This support needs some effort to enable some tools specially auto-complete, or intellisense, which saves a lot of time for developers.
We will start to make NetBeans support CakePHP. Firstly we need to create a cake project using cake command line tools.

1cd DOCUMENT_ROOT

2cake bake PROJECT_NAME

Then we need to create a NetBeans project using the create files. Click file > New Project, then choose New Project. From the window choose PHP from categories and from projects choose PHP Application with Existing Sources. Click Next then choose the project path. and click finish.

NetBeans New Project Dialog

After the project is created select the project in the Projects pane and right click Include Path. Click add folder and choose cake library path and add it. NetBeans will scan and add the library to its internal library.

NetBeans PHP include path dialog

Now you will have auto-complete working in your controllers, models, controllers, behaviors and helpers files. This will happen because NetBeans is smart enough to know that your inheriting AppController, AppModel,...etc which in turn inherits Controller and Model classes which is found in CakePHP library directory which NetBeans just scanned. But till now we don't have support for models and components included magically by CakePHP in controllers and models. To make NetBeans identifies those variables we will use PHPDoc trick. In your model or controller add a variable with the same name of your model or any other model you want, but make sure it is loaded as this will not include your model.

01class ProductsController extends AppController{

02    var $name = 'Products';

03 

04    /**

05     * @var Product

06     */

07    var $Product;

08 

09    /**

10     * @var EmailComponent

11     */

12    var $Email;

13}

You will notice that NetBeans enables auto-complete even in comments. Just hit Ctrl + Space when writing the name of any class. This will work with associated models in a model class.
Now you will notice that your CakePHP work is much more easier, but we still have auto-complete is not working in views. This problem can be solved using NetBeans feature which enables us to define a variable's type using comments. I call this feature var-doc or variable type notice. Just write a comment like this before any variable. You even can make this with $this variable to define the class you are working with as View class.

1/* @var $this View */

2/* @var $html HtmlHelper */

3/* @var $javascript JavascriptHelper */

4.....

This way you can have auto-complete support for your views and helpers included in views and you will notice that NetBeans also has support for your classes in comments.
At last the only thing that I couldn't have support for is behaviors methods which can be called from a model's instances if you now a way to do this please tell me. But we are waiting for more from NetBeans which has introduced too much for us, PHP Developers.

How to fix ubuntu high CPU temperature

2012-05-01T21:25:00.003-07:00

There is a common problem with some laptop owners with Ubuntu OS installed on their laptops to have high CPU heat issues. Especially after heavy load of applications running (especially 3D/Multimedia/Webcam applications), CPU temperature may rise through 70-80 celcius degrees. And that is a real dangerous and critical situation for hardware health. Dynamic CPU function at Ubuntu or the lack of hardware driver support that manufacturers share for Linux is causing that issue according to talks at Ubuntu Community Forums.

There are lots of complains about that situation and most of em were reported to Ubuntu developers but unfortunately yet Ubuntu has not shared any fix against that. Fortunately there is a solution for that.

Well this does not guarantee solving your heat issues but at least this solution worked for a lot of users (check Ubuntu community forums).

First of all be sure about that your laptop fans and components are cleaned because most of the cpu heat issues are related with that.

If you think that Ubuntu is the reason that causes the problem then you can try this solution. It worked for my Dell Inspiron N5010 laptop.

1) To monitor you cpu and other other components, install lm-sensors;

Open the terminal.

sudo apt-get install lm-sensors

After that ;

sensors-detect

and type Y to all questions, so it is going to install some modules to your kernel.

By typing sensors you can monitor your components.

2) Instal six important modules to fix your heat issue;

Open the terminal.

sudo gedit /etc/modules

Then add those lines save the editor and close;

#added to fix heat issue

battery
ac
thermal
processor
acpi-cpufreq
cpufreq-userspace

3) Restart Ubuntu and check the temperature values again by sensors command.

4) Try updating your hardware drivers. (Especially graphics card drivers)

If this does not solve your problem, avoid using Ubuntu till a solution for that appears. Because it may cause unfixable damages to your hardware.

How to add wordpress Uploader to plugins

2012-05-01T21:23:00.000-07:00

WordPress has a nice media uploader dialog that it uses on the editor pages. Now wouldn’t it be nice if you could use it to handle image uploads for part of a plugin or theme you’re writing? Maybe you want to add an easy way to change the logo in a theme? A simple “Upload Image” button would work quite well for that, wouldn’t it?

It’s fairly simple to implement, providing you already have a bit of experience with the WordPress API.
The first step is to prepare your HTML. Put it wherever the code for your admin page is. You want to have a text input for the image URL, and a button that will launch the uploader dialog.

<tr valign="top">

<th scope="row">Upload Image</th>

<td><label for="upload_image">

<input id="upload_image" type="text" size="36" name="upload_image" value="" />

<input id="upload_image_button" type="button" value="Upload Image" />

<br />Enter an URL or upload an image for the banner.

</label></td>

</tr>

Now that the easy part is out of the way, it’s time to start making it do something. You need to enqueue some scripts and styles. Here’s an example function to show how it’s done:

function my_admin_scripts() {

wp_enqueue_script('media-upload');

wp_enqueue_script('thickbox');

wp_register_script('my-upload', WP_PLUGIN_URL.'/my-script.js', array('jquery','media-upload','thickbox'));

wp_enqueue_script('my-upload');

}

function my_admin_styles() {

wp_enqueue_style('thickbox');

}

if (isset($_GET['page']) && $_GET['page'] == 'my_plugin_page') {

add_action('admin_print_scripts', 'my_admin_scripts');

add_action('admin_print_styles', 'my_admin_styles');

}

We need the media-upload and thickbox scripts for  starters, as well as jQuery, which is already included. Then we have to  register and enqueue our own JavaScript file, my-script.js, which will handle the media uploader functionality. We also need to load the thickbox stylesheet in the next function.

The if (…) block ensures that the scripts and styles will  only be included if the user is on a specific admin page. If you look at  your plugin’s (or theme’s) admin page, the URL should have a ?page=some_string at the end. Substitute my_plugin_page for that string.

Now for the part the actually invokes the uploader: the JavaScript. This will go in the my-script.js file we included earlier.

jQuery(document).ready(function() {

jQuery('#upload_image_button').click(function() {

 formfield = jQuery('#upload_image').attr('name');

 tb_show('', 'media-upload.php?type=image&amp;TB_iframe=true');

 return false;

});

window.send_to_editor = function(html) {

 imgurl = jQuery('img',html).attr('src');

 jQuery('#upload_image').val(imgurl);

 tb_remove();

}

});

The first click() event listener opens a ThickBox dialog  when the “Upload Image” button is clicked, and loads the uploader page  inside it. It also stores the name of the URL input field in a variable,  for later use.

The second function overrides the send_to_editor() function in the media-upload  script. This is probably the most important part. When the “Insert into  Post” button is clicked in the uploader dialog, this function fires. It  collects the URL of the image that was uploaded, dumps it into the  awaiting form field, and closes the ThickBox dialog.

That’s it. Providing everything went according to planned, you should  have a form field that will either accept an arbitrary image URL, or  allow a user to upload one on the spot.

how to Strip filename from a URL with php

2012-04-20T04:06:00.002-07:00

Using PHP, you might need to strip the path from a URL, leaving behind just the filename at the end of the URL. You can achieve this with a regular expression pattern of course, but I have a much simpler solution. See the example code below.

$url = "http://www.domain.com/path/to/file/filename.php";
$filename = basename($url);
echo $filename; //filename.php

And that’s all there is to it. I hope that you found this useful.

How to replace all instances of a character in a string with Javascript

2012-04-20T03:50:00.002-07:00

The easiest would be to use a regular expression with g flag to replace all instances:

str.replace(/foo/g, "bar")

This will replace all occurrences. If you just have a string, you can convert it to a RegExp object like this:

var pattern = "foobar",
    re = new RegExp(pattern, "g");

how to to add options to a select from an array with jQuery

2012-04-20T03:49:00.000-07:00

Using DOM Elements Creator plugin :

$.create('option', {'value': 'val'}, 'myText').appendTo('#mySelect');

Using the Option constructor (not sure about browser support):

$(new Option('myText', 'val')).appendTo('#mySelect');

Using document.createElement (avoiding extra work parsing HTML with $("<option></option>")):

$('#mySelect').append($(document.createElement("option")).attr("value","val").text("myText"));

how to Find base name in URL in Javascript

2012-04-20T03:48:00.000-07:00

Simply use this regex :

url.replace(/^.*\/|\.[^.]*$/g, '')

how to fix PHP Fatal error: Class ‘DOMDocument’ not found

2012-04-17T06:48:00.000-07:00

from the tail -f /var/log/httpd/error

[Tue Mar 10 16:01:30 2009] [error] [client 127.0.0.1] PHP Fatal  error:  Class 'DOMDocument' not found in /home/namran/src/....php on  line 15, referer: http://...

the solution turn out to be

yum install php-xml

How do I Find Out Linux CPU Utilization?

2012-04-07T06:13:00.004-07:00

Whenever a Linux system CPU is occupied by a process, it is unavailable for processing other requests. Rest of pending requests must wait till CPU is free. This becomes a bottleneck in the system. Following command will help you to identify CPU utilization, so that you can troubleshoot CPU related performance problems.
Finding CPU utilization is one of the important tasks. Linux comes with various utilities to report CPU utilization. With these commands, you will be able to find out:
* CPU utilization
* Display the utilization of each CPU individually (SMP cpu)
* Find out your system's average CPU utilization since the last reboot etc
* Determine which process is eating the CPU(s)

Old good top command to find out Linux cpu load

The top program provides a dynamic real-time view of a running system. It can display system summary information as well as a list of tasks currently being managed by the Linux kernel.
The top command monitors CPU utilization, process statistics, and memory utilization. The top section contains information related to overall system status - uptime, load average, process counts, CPU status, and utilization statistics for both memory and swap space.

Top command to find out Linux cpu usage

Type the top command:
$ top
Output:

You can see Linux CPU utilization under CPU stats. The task’s share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time. In a true SMP environment (multiple CPUS), top will operate in number of CPUs. Please note that you need to type q key to exit the top command display.
The top command produces a frequently-updated list of processes. By default, the processes are ordered by percentage of CPU usage, with only the "top" CPU consumers shown. The top command shows how much processing power and memory are being used, as well as other information about the running processes.

Find Linux CPU utilization using mpstat and other tools

Please note that you need to install special package called sysstat to take advantage of following commands. This package includes system performance tools for Linux (Red Hat Linux / RHEL includes these tools by default).
# apt-get install sysstat
Use up2date command if you are using RHEL:
# up2date sysstat

Display the utilization of each CPU individually using mpstat

If you are using SMP (Multiple CPU) system, use mpstat command to display the utilization of each CPU individually. It report processors related statistics. For example, type command:
# mpstat Output:

Linux 2.6.15.4 (debian)         Thursday 06 April 2006
05:13:05  IST  CPU   %user   %nice    %sys %iowait    %irq   %soft  %steal   %idle    intr/s
05:13:05  IST  all   16.52    0.00    2.87    1.09    0.07    0.02    0.00   79.42    830.06

The mpstat command display activities for each available processor, processor 0 being the first one. Global average activities among all processors are also reported. The mpstat command can be used both on SMP and UP machines, but in the latter, only global average activities will be printed.:
# mpstat -P ALL
Output:

Linux 2.6.15.4 (wwwportal1.xxxx.co.in)         Thursday 06 April 2006
05:14:58  IST  CPU   %user   %nice    %sys %iowait    %irq   %soft  %steal   %idle    intr/s
05:14:58  IST  all   16.46    0.00    2.88    1.08    0.07    0.02    0.00   79.48    835.96
05:14:58  IST    0   16.46    0.00    2.88    1.08    0.07    0.02    0.00   79.48    835.96
05:14:58  IST    1   15.77    2.70    3.17    2.01    0.05    0.03    0.00   81.44    822.54

Another output from my HP Dual Opteron 64 bit server:# mpstat -P ALLOutput:

Linux 2.6.5-7.252-smp (ora9.xxx.in)   04/07/06
07:44:18     CPU   %user   %nice %system %iowait    %irq   %soft   %idle    intr/s
07:44:18     all    3.01   57.31    0.36    0.13    0.01    0.00   39.19   1063.46
07:44:18       0    5.87   69.47    0.44    0.05    0.01    0.01   24.16    262.11
07:44:18       1    1.79   48.59    0.36    0.23    0.00    0.00   49.02    268.92
07:44:18       2    2.19   42.63    0.28    0.16    0.01    0.00   54.73    260.96
07:44:18       3    2.17   68.56    0.34    0.06    0.03    0.00   28.83    271.47

Report CPU utilization using sar command

You can display today’s CPU activity, with sar command:
# sar
Output:

Linux 2.6.9-42.0.3.ELsmp (dellbox.xyz.co.in)         01/13/2007
12:00:02 AM       CPU     %user     %nice   %system   %iowait     %idle
12:10:01 AM       all      1.05      0.00      0.28      0.04     98.64
12:20:01 AM       all      0.74      0.00      0.34      0.38     98.54
12:30:02 AM       all      1.09      0.00      0.28      0.10     98.53
12:40:01 AM       all      0.76      0.00      0.21      0.03     99.00
12:50:01 AM       all      1.25      0.00      0.32      0.03     98.40
01:00:01 AM       all      0.80      0.00      0.24      0.03     98.92
...
.....
..
04:40:01 AM       all      8.39      0.00     33.17      0.06     58.38
04:50:01 AM       all      8.68      0.00     37.51      0.04     53.78
05:00:01 AM       all      7.10      0.00     30.48      0.04     62.39
05:10:01 AM       all      8.78      0.00     37.74      0.03     53.44
05:20:02 AM       all      8.30      0.00     35.45      0.06     56.18
Average:          all      3.09      0.00      9.14      0.09     87.68

Comparison of CPU utilization

The sar command writes to standard output the contents of selected cumulative activity counters in the operating system. The accounting system, based on the values in the count and interval parameters. For example display comparison of CPU utilization; 2 seconds apart; 5 times, use:
# sar -u 2 5
Output (for each 2 seconds. 5 lines are displayed):

Linux 2.6.9-42.0.3.ELsmp (www1lab2.xyz.ac.in)         01/13/2007
05:33:24 AM       CPU     %user     %nice   %system   %iowait     %idle
05:33:26 AM       all      9.50      0.00     49.00      0.00     41.50
05:33:28 AM       all     16.79      0.00     74.69      0.00      8.52
05:33:30 AM       all     17.21      0.00     80.30      0.00      2.49
05:33:32 AM       all     16.75      0.00     81.00      0.00      2.25
05:33:34 AM       all     14.29      0.00     72.43      0.00     13.28
Average:          all     14.91      0.00     71.49      0.00     13.61

Where,

-u 12 5 : Report CPU utilization. The following values are displayed:

%user: Percentage of CPU utilization that occurred while executing at the user level (application).
%nice: Percentage of CPU utilization that occurred while executing at the user level with nice priority.
%system: Percentage of CPU utilization that occurred while executing at the system level (kernel).
%iowait: Percentage of time that the CPU or CPUs were idle during which the system had an outstanding disk I/O request.
%idle: Percentage of time that the CPU or CPUs were idle and the system did not have an outstanding disk I/O request.

To get multiple samples and multiple reports set an output file for the sar command. Run the sar command as a background process using.
# sar -o output.file 12 8 >/dev/null 2>&1 &
Better use nohup command so that you can logout and check back report later on:
# nohup sar -o output.file 12 8 >/dev/null 2>&1 &
All data is captured in binary form and saved to a file (data.file). The data can then be selectively displayed ith the sar command using the -f option.
# sar -f data.file

Task: Find out who is monopolizing or eating the CPUs

Finally, you need to determine which process is monopolizing or eating the CPUs. Following command will displays the top 10 CPU users on the Linux system.
# ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10
OR
# ps -eo pcpu,pid,user,args | sort -r -k1 | less
Output:

%CPU   PID USER     COMMAND
  96  2148 vivek    /usr/lib/vmware/bin/vmware-vmx -C /var/lib/vmware/Virtual Machines/Ubuntu 64-bit/Ubuntu 64-bit.vmx -@ ""
 0.7  3358 mysql    /usr/libexec/mysqld --defaults-file=/etc/my.cnf --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --skip-locking --socket=/var/lib/mysql/mysql.sock
 0.4 29129 lighttpd /usr/bin/php
 0.4 29128 lighttpd /usr/bin/php
 0.4 29127 lighttpd /usr/bin/php
 0.4 29126 lighttpd /usr/bin/php
 0.2  2177 vivek    [vmware-rtc]
 0.0     9 root     [kacpid]
 0.0     8 root     [khelper]

Now you know vmware-vmx process is eating up lots of CPU power. ps command displays every process (-e) with a user-defined format (-o pcpu). First field is pcpu (cpu utilization). It is sorted in reverse order to display top 10 CPU eating process.

iostat command

You can also use iostat command which report Central Processing Unit (CPU) statistics and input/output statistics for devices and partitions. It can be use to find out your system's average CPU utilization since the last reboot.
# iostatOutput:

Linux 2.6.15.4 (debian)         Thursday 06 April 2006
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
     16.36    0.00    2.99    1.06    0.00   79.59
Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
hda               0.00         0.00         0.00         16          0
hdb               6.43        85.57       166.74     875340    1705664
hdc               0.03         0.16         0.00       1644          0
sda               0.00         0.00         0.00         24          0

You may want to use following command, which gives you three outputs every 5 seconds (as previous command gives information since the last reboot):$ iostat -xtc 5 3

GUI tools for your laptops/desktops

Above tools/commands are quite useful on remote server. For local system with X GUI installed you can try out gnome-system-monitor. It allows you to view and control the processes running on your system. You can access detailed memory maps, send signals, and terminate the processes.
$ gnome-system-monitor

(Click to enlarge image)
In addition, the gnome-system-monitor provides an overall view of the resource usage on your system, including memory and CPU allocation.

(Click to enlarge image)

HOW TO Install phpMyAdmin in CentOS

2012-03-28T08:34:00.000-07:00

I am using CentOS 5 in one of my Virtual Servers and I wanted it to have phpMyAdmin. I tried installing it by doing yum install phpmyadmin but it said No package phpmyadmin available. So I add to add a repo. I discovered that rpmforge repo had this package. To add it, I executed the following commands:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.1-1.el5.rf.i386.rpm
rpm -Uhv rpmforge-release-0.5.1-1.el5.rf.i386.rpm

If you have 64-bit version installed, you should try this one out:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.1-1.el5.rf.x86_64.rpm
rpm -Uhv rpmforge-release-0.5.1-1.el5.rf.x86_64.rpm

If you get a 404 Not Found, then you will need to figure out the latest updated version of repo url from rpmforge usage page.
After that, you may like to update your packages by doing this:

yum update

and then continue installing phpmyadmin

yum install phpmyadmin

It should ask you for confirmation and you can continue installing phpMyAdmin with dependencies.
When installation is done, you can edit /etc/httpd/conf.d/phpmyadmin.conf and allow it to be opened from anywhere and not just the same computer. You are going to need this if you have installed it in a remote virtual server.
To do so, open up /etc/httpd/conf.d/phpmyadmin.conf using:

nano /etc/httpd/conf.d/phpmyadmin.conf

You will see:

<Directory "/usr/share/phpmyadmin">
  Order Deny,Allow
  Deny from all
  Allow from 127.0.0.1
</Directory>

Just change the line “Allow from 127.0.0.1″ to “Allow from [yourip]“, where [yourip] is IP address of your computer if you have public static IP. Otherwise, you can also set it to “Allow from all”.
Press Ctrl+O followed by Enter to save and Ctrl+X to exit nano.
Now, you must restart apache. To do so, run

service httpd restart

Now, you can access phpMyAdmin by visiting http://vps_server_IP_or_domain/phpmyadmin. But you will get the following error:

Error
The configuration file now needs a secret passphrase (blowfish_secret).

To make it work, you will need to edit config.inc.php. To do so, type in:

nano /usr/share/phpmyadmin/config.inc.php

Find a line saying:

$cfg['blowfish_secret'] = ''; /* YOU MUST FILL IN THIS
FOR
COOKIE AUTH! */

Fill in any secret keyword there, eg mysecretpassphrase, so that it looks like:

$cfg['blowfish_secret'] = 'mysecretpassphrase'; /* YOU MUST FILL IN THIS
FOR
COOKIE AUTH! */

and then save it.
If you don’t have mysql server installed, you will get the following error:

Error
#2002 – The server is not responding (or the local MySQL server’s socket is not correctly configured)

To install mysql-server, just run:

yum install mysql-server

and then start it:

service mysqld start

Then change the root password:

mysqladmin -u root password PASSWORD_HERE

Now, you will have to remove phpmyadmin:

yum remove phpmyadmin

and reinstall it again:

yum install phpmyadmin

Then you will need to edit the config.inc.php again to enter blowfish secret (see above). Then, you can login.
If however, you want phpMyAdmin to connect to a remote server, you can change the line by replacing localhost with your server IP:

$cfg['Servers'][$i]['host'] = 'localhost';

Hope this helps.

how to fix : No activity within 1800 seconds; please log in again

2012-03-28T07:44:00.002-07:00

1800 seconds is such a long time, right?

It’s 30 minutes.
It’s 0.5 hours.
It’s 0.0208333333 days.
It’s also 5.70397764 × 10^-5 years.

And it’s not long enough for me. phpMyAdmin logs you out after 1800 seconds, obviously for security reasons. That’s fine if there are other people about, if I was in an office with people coming and going, but I work from home. All I see for most of the day is my family, the radio, my messy desk, computers, and the view out the window. Time to figure out how to make that 1800 second limit a little longer or remove it altogether.
After a little digging, I discovered that extending the time limit to a day is actually quite easy. Open your phpMyAdmin’s config.inc.php and search for or add the following line:

$cfg['LoginCookieValidity'] = 86400;

Refresh your logged out phpMyAdmin and presuming you haven’t left it idle for 24 hours, you’ll be logged in again!
If the time limit really bugs you, you need http authentication. Look for the “auth_type” line in the config.inc.php and change that to “http”. phpMyAdmin won’t log you out as long as your browser is open. Perfect!
If you’re concerned about sending your MySQL username and password in the clear each time you make a request to phpMyAdmin you can either use SSL or try the “config” auth_type. Make sure you fill in the username and password fields in the config file, and secure the phpMyAdmin directory with a htpasswd file.

How to Install php-mcrypt on CentOS 6.2

2012-03-28T03:28:00.000-07:00

Symptoms :
This error appeared when i try to use phpmyadmin on authentication type as cookie. mcrypt is necessary if you want to use cookie based authentication with phpymyadmin.

The mcrypt exension is missing. Please check your PHP configuration.

To install php-mcrypt on CentOS 6.2, follow the following steps :
1. Download epel repository :

[root@centos62 ~]# [root@centos62 ~]# wget http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-5.noarch.rpm
[root@centos62 ~]# wget http://ftp.riken.jp/Linux/fedora/epel/RPM-GPG-KEY-EPEL-6

2. Install epel repository :

[root@centos62 ~]# rpm --import RPM-GPG-KEY-EPEL-6
[root@centos62 ~]# rpm -i epel-release-6-5.noarch.rpm

3. Simply run the following command to install php-mcrypt :

[root@centos62 ~]# yum install php-mcrypt -y

How to check CentOS version via command line?

2012-03-28T03:24:00.002-07:00

Via command line, type this:

cat /etc/redhat-release

To safely upgrade CentOS to the latest version, type this:

yum update

PHP jQuery AJAX Javascript Long Polling

2011-10-16T09:25:00.000-07:00

Background

"Long polling" is the name used to describe a technique which:

An AJAX request is made (utilizing a javascript framework such as jQuery)
The server waits for the data requested to be available, loops, and sleeps (your server-side PHP script)
This loop repeats after data is returned to the client and processed (usually in your AJAX request's onComplete callback function)

This essentially simulates a continuous real-time stream from the client to the server. It can be more efficient than a regular polling technique because of the reduction in HTTP requests. You're not asking over and over and over again for new data - you ask once and wait for an answer. In most cases this reduces the latency in which data becomes available to your application.
There are a variety of use cases in which this technique can be handy. At the top of the list are real-time web-based chat applications. Each client executes a long polling loop for chat and user events (sign on/sign off/new message). Meebo is perhaps the greatest example of this.
It's important to note some of the server side technical limitations of long polling. Because connections remain open for considerably longer time than a typical HTTP request/response cycle you want your web server to be able to handle a large number of simultaneous connections. Apache isn't the best candidate for this type of situation. nginx and lighttpd are two lightweight web servers built from the ground up to handle a high volume of simultaneous connections. Both support the FastCGI interface and as such can be configured to support PHP. Again, Meebo uses lighttpd.
For similar reasons - it's also a good idea to choose a different sub-domain to handle long polling traffic. Because of client side browser limitations you don't want long polling connections interfering with regular HTTP traffic delivering page and media resources for your application.

Implementation

jQuery makes implementation a breeze.

var lpOnComplete = function(response) {
    alert(response);
    // do more processing
    lpStart();
};
 
var lpStart = function() {
    $.post('/path/to/script', {}, lpOnComplete, 'json');
};
 
$(document).ready(lpStart);
 
 

Straightforward. When the document is ready the loop begins. Each iteration the returned data is processed and the loop is restarted.
On the server side - just like we discussed earlier:

$time = time();
while((time() - $time) < 30) {
    // query memcache, database, etc. for new data
    $data = $datasource->getLatest();
 
    // if we have new data return it
    if(!empty($data)) {
        echo json_encode($data);
        break;
    }
 
    usleep(25000);
}
 

Actually, a couple points of interest here. We don't actually loop infinitely server side. You may have noticed the logic for the while loop - if we've executed for more than 30 seconds we discontinue the loop and return nothing. This nearly eliminates the possibility of substantial memory leaks. Also, if we didn't put a cap on execution time we would need to print a "space" character and flush output buffers every iteration of the loop to keep PHP abreast to the status of this process/connection. Without output being sent PHP cannot determine if the connection was lost via connection_status() or connection_aborted(). As a result this could lead to a situation where there are an increasing number of "ghost" processes eating up server resources. Not good!
That pretty much sums it up! Not that difficult, right?