All cluster admin starts with the main head node, which normal users do not have access to. 
To log in directly from outside the cluster ssh to `stri-cluster.herts.ac.uk`. 
If already logged in to another cluster machine, you can ssh to `head.data`. 

Once logged in to this machine (which calls itself `‘uhhpc’`) you may use `sudo` to carry out sysadmin tasks. 
This has the advantage that it doesn’t leave you sitting at a root prompt. 

Sudo will prompt you for your own password. You do not need to know the root password to use sudo. 

You may of course use this to get a root prompt on another machine by doing e.g. `sudo ssh node001`. 
Sudo is not set up on other machines. However, please use sudo if possible on `uhhpc` rather than a root prompt.