After upgrading an environment from ESX5 to ESX5U1, I noticed syslog stopped working. Since ESXi by default does not keep log messages across reboots, it is a must to either specify a syslog server to collect the log files, or set the log directory to a shared datastore.
In this environment I used syslog to log all messages from the ESX hosts to a central syslog server.
When checking the syslog server after the upgrade, I noticed there where no more log messages arriving at the syslog server, and confirmed there used to be log messages just prior to the upgrade. Continue reading