Detecting if system is running CloudLinux/CloudLinux kernel:
$ uname -r|grep lve
If you get an output, it means the system is running CloudLinux kernel. CloudLinux kernels have lve in its name, like: 2.6.32-458.18.1.lve1.2.44.el6.x86_64
Alternatively you can check for the presence of /proc/lve/list file.
Check if CageFS is enabled (as root):
$ /usr/sbin/cagefsctl --cagefs-status
Check if CageFS is enabled for a particular user (as root):
$ /usr/sbin/cagefsctl --user-status _USER_NAME_
Check if you are inside CageFS:
Check for the presence of /var/.cagefs/.cagefs.token file - if present, it means that you are inside CageFS.