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Oracle Linux, virtualization , Enterprise and Cloud Management Cloud technology musings

  • October 15, 2014

Oracle Linux Containers and docker and the magic of ksplice becomes even more exciting

So, in my previous blogs I talked about the value of ksplice for applying updates and keeping your system current. Typical use case has been on physical servers running some application or in a VM running some application and it all keeps every system pretty isolated. Downtime on a single server is often, by a system admin, seen as no big deal, downtime of a bunch of servers because of a multi-tier application that goes down, however, by the application owner is a pretty big deal and can take some scheduling (and cost) to agree on downtime for reboots. If you have to patch a database server and reboot it, then you first have to bring down your application servers, then bring down the database, then reboot the server. So that 'single reboot' from a sysadmin point of view, is a nightmare and long downtime and potential risk for the application owner that has an application across many servers. Do keep that complexity in mind...

Anyway, we introduced support for Linux containers a year ago, back with Oracle Linux 6 and the release of UEKr3, no need to wait for OL7 (or rhel7...) we 've been doing this for almost a year and it was possible without having to reinstall servers and go from 6 to 7 and to systemd and have major changes. Just simply updating an OL6 environment and a reboot into uek3 and you were good to go, a year ago. So... with containers (and docker is very similar here)... you run one kernel. As opposed to running VMs where each VM is a completely isolated virtual environment with their own kernel and you can live migrate the VMs to another host if you need to update/patch the host, etc... So you run an OS that supports containers, you deploy your apps and isolate them nicely in a container each... and now you need to apply kernel security updates... well... that means, the host kernel on which all these containers environments are running... oops. my reboot now brings down a ton of containers. Well, not with ksplice. You run uptrack-update in the main environment and it nicely, online, without affecting your running apps in their containers or docker environments, updates to the latest fixes and CVEs. Done. No downtime, no scheduling issues with your application users... all set.

Supported.. since a year ago. Stable.

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