A kernel upgrade on a Coordinating Node requires a system restart. Restarting a CN requires that the environment is placed in read-only mode to help avoid content inconsistency between the CNs operating within an Environment. Restarting the Primary CN in an Environment requires that the Environment DNS be switched to another CN so the read only service (resolution, retrieval, and search) remain available to clients. The DNS switch is required in the production environment and is optional in the various test environments.
Figure 1. Typical setup of Coordinating Nodes in an environment. When restarting CN-1 it is necessary to change the Environment DNS to point to one of the other nodes so that operations such resolve and external applications (e.g. Search UI) continue to function.
Set read-only mode
Update non-primary nodes (Indexing CN and Third CN), avoiding an update of DataONE packages:
#optional hold on DataONE packages sudo apt-mark hold dataone* sudo apt-get update sudo apt-get dist-upgrade #when ready, restart the server sudo reboot
#undo hold on DataONE packages sudo apt-mark unhold dataone* # verify new kernel running uname -r
Switch DNS to a non-primary node. For example, switch the environment DNS entry to point to the Indexing CN.
Update the remaining node. As for #4.
Switch DNS back to the original primary node.
Leave read-only mode