Speed Up and Secure SSH to Linux by Disabling GSSAPI-Authentication

Every time you try to connect with SSH after you enter your username, GSSAPI Authentication will attempt to authenticate you using the Kerberos protocol.

The problem with this is that nobody sets up GSSAPI Authentication services: this is both a waste of time and a security risk, as you are attempting to authenticate a service that you're not hosting, and is therefore prone to "Man in the Middle" attacks.

Unfortunately, GSSAPI Authentication with SSH in Linux is the default option. You can easily turn it off by doing the following. Open the SSH config file...

[user@localhost /]$ vi etc/ssh/ssh_config

And then find this line...

Host *
GSSAPIAuthentication yes

You may not have GSSAPIAuthentication set there yet, but you will want to find the line beginning with Host *. And then you can adjust it like so...

Host *
GSSAPIAuthentication no

Now your SSH will load instantly and securely.

Using HTAccess to Redirect All Users (and POST data) to the Same URL

With the Apache .htaccess file, you can control a good number of things on your server.

If you turn on the RewriteEngine, you can have one URL example.com/123, always return the results of another URL, like example.com/index.php?id=123.

To do this, you need to have a .htaccess file in the base directory of your apache htdocs folder. It should start with this...

RewriteEngine On
RewriteBase /

And, it can redirect everyone to index.php with this...

RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ index.php [QSA,NC,L]

You can change index.php to anything you like, of course. Then you can get the information about the original URL by using the $_POST parameters, which you can see with...

print_r($_POST);

How to Grep files in Linux, but only certain file extensions?

Want to search your file system on Linux?  It's easy!

    grep -r --include=\*.txt 'searchterm' ./

...or case-insensitive version...

    grep -r -i --include=\*.txt 'searchterm' ./

• grep : command
  
• -r : recursively
  
• -i : ignore-case
  
• --include : all *.txt: text files (escape with \ just in case you have a directory with asterisks in the filenames)
  
• 'searchterm' : What to search
  
• ./ : Start at current directory.

Installing Apache, PHP, and ImageMagick together using Linux/CentOS

There is a big disclaimer that should be made to all those about to venture on ImageMagick programming using PHP: the great, vast majority of WAMP (Windows-Apache-MySQL-PHP) servers do not support ImageMagick commands at all, since it is a "different package," and there appears to be no way to install ImageMagick through standard Add/Remove Applications within Linux (as far as standard Debian linux releases go).  It's very easy to get Apache/PHP running in either Windows or Linux with pretty much any standard OS/distro supported so that you can run all of your own code on your own computer.  But that's definitely not the case when you want Imagick to cooperate with your Apache server and your PHP code!

It took me almost an entire week just to get Apache/PHP/ImageMagick working all together nice and happily so that I could run my own PHP code on my own machine (natively, too).  So, I decided to simply write down the steps, to help anyone else out who could need help.

Guide to Building an Apache/PHP/Imagick Server with Linux/CentOS 6.4:::

1. Install CentOS 6.4.  (Theoretically, other versions of CentOS should work as well, but I simply chose the most recent one.)  Also, you can very easily emulate CentOS within Windows (for instance, the unfree choice of VMWare).
2. Install PHP, PHP-Common, PHP-extensions, etc., from standard Application Package Manager ("Add/Remove Programs", usually in system tools somewhere).  (You don't have to worry about Apache, because that comes with CentOS 6.4 anyway.)
3. Open up a terminal and enter admin mode with the command "su".  You'll need a password for this.
4. Enter this command: yum install ImageMagick ImageMagick-devel
5. Enter this command: pecl install imagick
6. Modify php.ini and include the line "extension=imagick.so".  This file is located at "/etc/php.ini" normally.  The line must be exactly inserted in the section of "Dynamic Extensions", which begins with this commented out text:

--------------------------------
;;;;;;;;;;;;;;;;;;;;;;
; Dynamic Extensions ;
;;;;;;;;;;;;;;;;;;;;;;
--------------------------------

Use the "search" feature of gedit to find the text.  Add the extension below the commented out note in this section so that the result looks like:

--------------------------------
;;;;
; Note: packaged extension modules are now loaded via the .ini files
; found in the directory /etc/php.d; these are loaded by default.
;;;;

extension=imagick.so
--------------------------------

Putting the extension directly at the top caused me serious permission issues in running Imagick code.  Also, with CentOS, the permissions automatically disable user control for this php.ini.  Enter the following terminal command: "chown [YOUR-USERNAME] -R /etc/php.ini", without the quotes to get control to modify it.  Note to insert your username where it states "[YOUR-USERNAME]".
7. Enter this command: "service httpd restart", without quotes, from admin mode.  This restarts Apache/PHP/PHP's extensions now that you've installed ImageMagick.  If this gives you an error, just try "service httpd start".

My favorite part about this method is that you can update your system with issuing the "yum update" command and then the "yum upgrade" command -- and the Apache/PHP/Imagick combination will still be working perfectly!  Unlike some other guides out there for this, you don't need to rely on antiquated, unsupported versions that can be nearly impossible to find.  Also, you don't need to worry about the MySQL, Hash, MBString, Exif packages, because they all seem to be installed and properly cooperating with PHP automatically after installing PHP from the Application Manager.  This solution makes everything work well together.

The root directory of your public files is located at /var/www/html/.  Normally, this folder is not owned by the user, so you'll get a permission error when trying to add files or folders to it.  Correct that with entering admin mode in the terminal/command-line window ("su" command) and entering the following command: "chown [YOUR-USERNAME] -R /var/www/html/", without quotes.  Again, replace "[YOUR-USERNAME]" with your actual user name.  (Warning: The first time I did this, I was lazy and entered the command for only the "/var/" folder, which prevented my system ever from booting.  It would always freeze with the notorious and googleable error-message: "Could not update ICEauthority file /var/lib/gdm/.ICEauthority".  So, make sure to change ownership only for "/var/www/html/".)

To view your root directory files as compiled, resultant, PHP pages, open up a browser and enter "127.0.0.1" as the address.  So, a file in your root directory would be accessed at the following URL in your browser: http://127.0.0.1/your.file.php .  If you get a "could not connect" error message, try the command "service httpd start" at the terminal window from admin mode.  (You have to start this service manually every time the machine boots, although there's plenty of ways to automate it.)

I hope this helps!  I tried a hundred different guides on getting Apache/PHP/Imagick to work together and none of them worked.  Don't give up!  ImageMagick is a package of really neat imaging functions!