Instructions are here, reposted for my own convenience:

This is for Ubuntu Server 12.04 64-bit.

edit /etc/apt/sources.list and add to the bottom:

deb http://dl.ajaxplorer.info/repos/apt/ stable main
deb-src http://dl.ajaxplorer.info/repos/apt/ stable main

Then, install the gpg key

wget -O - http://dl.ajaxplorer.info/repos/charles@ajaxplorer.info.gpg.key | sudo apt-key add -

Lastly:

sudo apt-get update
sudo apt-get install ajaxplorer

A few more steps to get it working…

copy the sample config file over (and make it readable by the web server):

cp /usr/share/doc/ajaxplorer/apache2.sample.conf /etc/apache2/sites-enabled/ajaxplorer.conf
chown www-data:www-data /etc/apache2/sites-enabled/ajaxplorer.conf

Restart apache…

service apache2 restart

…or…

/etc/init.d/apache2 restart

Make AjaXplorer redirect to HTTPS… (this is displayed during the initial page visit anyway)

edit /usr/share/ajaxplorer/conf/bootstrap_conf.php and uncomment the following line (or add it to the bottom)

define("AJXP_FORCE_SSL_REDIRECT", true);

If HTTPS doesn’t load, it’s probably because apache isn’t configured for SSL. That’s in the next section.

If you get a warning about Server charset encoding, uncomment this line in /usr/share/ajaxplorer/conf/bootstrap_conf.php

define("AJXP_LOCALE", "en_US.UTF-8");

Lastly, since I have /srv on a separate partition, I want ajaxplorer data stored there. By default it’s stored in /usr/share/ajaxplorer/data, which is actually a symlink to /var/lib/ajaxplorer/data.

mkdir /srv/ajaxplorer
cp -r /var/lib/ajaxplorer/data/* /srv/ajaxplorer
chown -R www-data:www-data /srv/ajaxplorer
rm /usr/share/ajaxplorer/data
ln -s /srv/ajaxplorer /usr/share/ajaxplorer/data

Warning: AjaXplorer will start acting odd if /srv isn’t mounted at boot time. Keep that in mind.

By default, PHP max file upload is 2M, and this setting will carry over to AjaXplorer. In order to increase it, you have to change it in three places.  The AjaXplorer documentation says that this is set by php’s upload_max_filesize, but I’ve found that you also have to change php’s post_max_size to match. (/etc/php5/apache2/php.ini). After which, go into AjaXplorer settings repository, then Global Configurations > Core Configs > Common ‘uploader’ core configs. Expand Limitations, then set File Size to 0 to inherit the PHP setting. (Note: It won’t stay 0, it will auto-set to php’s setting. Keep this in mind if you want to change it later.)

More later…