Here is the tips how to boot into single user mode on CloudLinux OS
step 1: At the GRUB splash screen at boot time, press any key to enter the GRUB interactive menu.
step 2: type c (goes to grub command line) then hit esc
step 3: Select Cloud Linux with the version of the kernel that you wish to boot and type a to append the line.
step 4: type single and hit enter to boot
source: http://quags.net/archives/73