13 January 2018
This is going to involve a series of 'maintenance windows' where the physical servers are shut down and rebooted. Downtime in each case could be up to 2 hours. See the link below for details.
When we know the schedule we will post details here. According to Linode we should have at least a days notice in each case.
Update: All of our servers are running with updated kernels, and our final web server is undergoing hardware maintenance today (17 Jan).