How to install ngx_pagespeed Module in ubuntu 14.04 where nginx server is already installed?

This question was answered by @jefftk:

Saurabh is correct: you first have to remove the nginx installed by your package manager, and then build from source following the instructions you referenced.

But I did just want to clear up a couple side things:

• Google hasn’t donated ngx_pagespeed to the Apache Foundation. Perhaps you’re thinking of mod_spdy?
• The reason we provide binary packages for Apache but not Nginx is that Apache supports loadable modules and Nginx doesn’t. If Nginx adds support for packages we’ll gladly prepare them.

(I’m a developer on PageSpeed at Google.)

You can see the comment here.

This question was answered by @saurabh:

Hey. Once this is already installed, it is not possible to compile it with the module thereafter. Also hopefully you are already aware that this mod has been officially donated by Google to Apache and that is the primary reason Google offers “Build From Source” code and for Apache it is pre-built!

Yet if you want to compile it again, you only need to do this:

sudo apt-get remove --purge nginx
sudo apt-get autoremove
sudo apt-get autoclean

Once you have completely removed Nginx, then you will be required to follows steps as described on this page.

Hope this helps!

– Regards Saurabh

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You can see the comment here.