FWIW the OP mentioned that his server restarted itself. It sounds to me like your issue is different.
However, I'm 99% sure I know why you are having issues. xcache is the default php 5.4 caching app. But it is incompatible with Moodle 2.7 (and no doubt other new php web apps). I you check the apache error log (in /var/log/apache2/error.log) I'm sure that you'll see segfaults in there (caused by the xcache incompatibility...)
To install Moodle 2.7 on TKL v13 LAMP have a read of this post.
TBH I'm not sure you're having the same issue...
FWIW the OP mentioned that his server restarted itself. It sounds to me like your issue is different.
However, I'm 99% sure I know why you are having issues. xcache is the default php 5.4 caching app. But it is incompatible with Moodle 2.7 (and no doubt other new php web apps). I you check the apache error log (in /var/log/apache2/error.log) I'm sure that you'll see segfaults in there (caused by the xcache incompatibility...)
To install Moodle 2.7 on TKL v13 LAMP have a read of this post.