Shutdowns and Reboots
Power Saving
Most of the Maths Linux computers will shut down automatically when they have been idle and unused for half an hour. (To be precise, the machine checks for user processes every 30 minutes. If it finds nothing on two successive checks, it will shut itself down.) There are exceptions for servers including machines which NFS-export data spaces, so you won't find yourself cut off from your data because the computer on which it is stored is down.
Windows computers will go into hibernation when they have been idle for a period of time, whether anyone is logged in or not.
Security Reboots
The below is planned to change so that machines will reboot overnight for security updates rather than having a reboot window.
Linux computers will reboot in the early hours of Wednesday morning if needed to install security updates including a new kernel. These regular reboots are unannounced and Wednesday 4:00-6:00am should be considered a vulnerable period. The best way to minimise the disruption this causes is to get into the habit of logging off when you have finished using your computer for the day. This gives it a chance to reboot when you are not using it, so that it doesn't need to reboot when you are using it.
Note: if you are leaving your computer idle and it is failing to switch itself off, a process has probably got stuck. You may be able to shut it down manually.
If there is a critical security update it may be necessary to reboot the Linux computers at short notice.
No attempt is made to protect long running jobs from being killed by the security reboots, and you must ensure that your jobs checkpoint regularly.
Advice and policies on long jobs
The security reboots are advertised on the Maths Computing News page. You can also sign up to hear about them by email:
Shutting Down and Rebooting Your PC
You can shut down or restart a Maths Linux PC in the same way that you would shut down a personal Linux laptop - via the power icon or by typing shutdown or reboot. We have configured Ubuntu 16.04 so that this will not work if someone else is using the computer. Under these circumstances, please email help@maths explaining why you needed to switch off the machine and we will investigate.
If you have a reasonably new Linux PC (less than 5 years old) in your office, be aware that other people may want to use it for number-crunching jobs.
- It's fine to disconnect the monitor, keyboard or mouse for use with your laptop, but please leave newer Linux PCs connected to power and network.
- Unplugging PCs from the network so you can plug in your laptop won't work because laptops are connected to a separate network. Please email help@maths to request a laptop network connection in your office if the wifi is not sufficient.
- If you want your PC removed from your office email help@maths. We may be able to find it a good home.
- If your PC is making a lot of noise email help@maths.
- If your PC is overloaded with someone else's jobs please contact them directly. Our policy on running long jobs
Windows computers can be rebooted via the "Sleep, Shutdown or Reboot" desktop icon. If you need to shut down a Windows machine please email help@maths.
Waking up PCs Remotely
Alternatively, you can use ssh.maths.cam.ac.uk which is always switched on.
