Hello and welcome to the forums.
Note: This discussion was moved from the VMware vSphere Storage community to the Virtual Machine & Guest OS community.
VMware kb 1035655 has instructions for this procedure on the VMware Management Appliance, but they should be basically the same. Make sure you have a backup, before you try any of these changes.
Good Luck!
welcome to the community - The first step would be increase the size of the virtual disk that has the /sys partition on it - the from within the guest o/s you will need to expand the paritition.
To extend the partition you need LVM on Linux. If is not enable I suggest to go to a simple way: add a new disk, copy the data, mount the new disk in /sys instead of the existing one and then delete the old disk.
Andre