Changing Partition Attributes (such as securing tmp) do not need a reboot.
You can remount the partition immediately with the new attributes doing something like…

mount -o remount,noexec,nosuid /tmp or

make the change in the fstab

LABEL=/tmp              /tmp                    ext3    noexec,nosuid,nodev,rw  1 2

then remount it mount -o remount /tmp

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The following is how to secure your /TMP directory using a cPanel Script.
You MUST have cPanel installed for this to work.

1. Login to your server as root via SSH.
2. Type: /scripts/securetmp

That’s it your done. cPanel wrote that script to allow users to secure their /TMP Directory very easily.