This morning, after a reboot of fileserver zwik4 at around 06:30, its NFS server did not start correctly. This affected several users who were unable to log in to login nodes such as lilo and cnlogin22; clusternode and JupyterHub users were probably affected as well.

We rebooted zwik4 again at around 11:10, after which the NFS server started without problems and the login nodes were reachable again.

We do not yet know why this happened. The error we saw, “address already in use”, was quite unexpected, and the problem appears to have been temporary. We will investigate further and update this message if we learn more.