I ran into a strange problem after upgrading to wordpress 3.5.1.  I’ve read that this problem can affect some hosted wordpress instances as well (though not wordpress.com).  Most of the other posts in wordpress support forums point to a plugin or theme that has some broken javascript.  After disabling all of my plugins and reverting to the default wordpress theme, my issue persisted.  I wasn’t able to get the javascript media upload to work.  My “add media” button and “Set featured image” links didn’t work on any of my pages.

I finally came across a post in the wordpess forums that pointed to mod_pagespeed as the culprint.  The .js files in /wp-admin/ are already minified, and mod_pagespeed attempts to compress them again.  As a result, the javascript doesn’t work.

The quick solution?  Add the following to your .htaccess file in the /wp-admin/ directory:

ModPagespeedDisallow *

This will keep mod_pagespeed from compressing anything in your /wp-admin/ directory, and your javascript now works.  If your web host allows .htaccess directives, this should also work for hosted wordpress instances.

I have several apache servers that sit behind various load balancing appliances and assorted reverse proxy servers.  I don’t maintain the proxies and from time to time I have the need to allow/block IPs and ranges of IPs from my web servers.

Normally my .htaccess files contain something like this:

Order deny,allow
Deny from all
Allow from 192.168.1.0/24
Allow from 10.0.6.0/24

If you’ve got a reverse proxy in front of your web server, all of the traffic appears to originate from the proxy instead of the true origin.  You can use the apache’s mod_setenvif to extract the original IP address (the X-Forwarded-For value) and then use some regex to update your allow/deny rules.  Your rules then look like this:

Order deny,allow
Deny from all
SetEnvIF X-Forwarded-For "^192\.168\.1\.([1-9]|[1-9][0-9]|1([0-9][0-9])|2([0-4][0-9]|5[0-4]))$" AllowThisSubnet
SetEnvIF X-Forwarded-For "^10\.0\.6\.([1-9]|[1-9][0-9]|1([0-9][0-9])|2([0-4][0-9]|5[0-4]))$" AllowThisSubnet
Allow from env=AllowThisSubnet

If you’re like me and not a regex master, Google analytics (and I’m sure other places) has this helpful calculator to generate the regular expressions that you need on your SetEnvIF lines.

I enjoy hacking on old hardware and making linux run on things that weren’t designed to run it.  It’s not a very productive way to use time at home, but I end up learning a lot about the inner working linux.  It’s how I taught myself to use linux in the mid 90′s.  It’s great fun (!?) and you’ll learn how linux works.

I also highly discourage doing this at work and on any production level machines in your life.  Use the -stable branch.  Use the LTS version. Life is much easier when you follow that path.  You’ll also be much more productive because you’re spending less time compiling modules and more time writing code that contributes to the bottom line of your business.

Occasionally, these two path cross.  I normally don’t have bleeding edge workstations to deal with, but this month I did.  The HP Z220 is a fabulous piece of hardware.  Xeon processors and solid state drives are amazing.  The problem is that the built in Intel HD4000 graphics adapter will only mirror the display to the HP display port with the xorg modules that are currently in Ubuntu 12.04. I didn’t want to upgrade to 12.10, so the next best solution was to update the kernel.  I have tested this process only with a 3.6.x kernel.  I’ve read that 3.4.x might work, but I have failed to get it to work with a 3.2.x kernel.  Kernel 3.6.0 is available from Quantal mainline, and here’s a guide to install the it in 12.04 if you need such a thing.  That’s still doesn’t fix the display port issue.  You still wont’ be able to extend the display, but kernel 3.6.0 will correctly identify the chipset as Ivybridge.

You’ll now need a PPA with updated intel and mesa packages.  I’m using Oibaf’s repo which you can add by executing:

sudo apt-add-repository ppa:oibaf/graphics-drivers
sudo apt-get update
sudo apt-get upgrade

Reboot and go to display settings and you should now be able to uncheck the ‘Mirror Displays’ option and extend your desktop to a second display device.