If your /tmp partiton is filling up fast lor your server was installed with too small of tmp partiton then this is an easy way to get it done on cpanel servers.
From 1-2 gb is needed on most mid to high usage servers.
First edit /scripts/securetmp and look for the current size, change it to your desired size.
Then umount /tmp and /var/tmp:
umount -l /tmp
umount -l /var/tmp
Then remove the partition file:
rm -fv /usr/tmpDSK
Then create a nice new one:
/scripts/securetmp
And that is it.