/etc/init.d/cpanel stop
/etc/init.d/httpd stop
/etc/init.d/lsws stop
/etc/init.d/mysql stop

umount -l /tmp
umount -l /var/tmp
Move /usr/tmpDSK file to another location (just in case you’ll need to mount it somewhere else to preserve data):

mv /usr/tmpDSK /usr/tmpDSK_back
Modify /scripts/securetmp to set tmpdsksize to desired size:

vi /scripts/securetmp
$tmpdsksize = 2048000

/scripts/securetmp

Start cpanel, apache (litespeed), mysql services:
/etc/init.d/cpanel start
/etc/init.d/httpd start
/etc/init.d/lsws start
/etc/init.d/mysql start