Ksplice works on an unmodified stock Linux kernel and functions by examining a unified diff and the original Linux kernel source code, then analyzing that compared to the running kernel to be able to update the areas of the kernel where the security update resides. Processes are automatically turned off while loading the new kernel code into system memory and then automatically resumed afterwards. Ksplice is mainly targeted for enterprise environments where downtime must be at a minimum and security updates are critical.
Up to now, Ksplice has been offered for free to Ubuntu and Fedora users while a product subscription is required for Red Hat Enterprise Linux, CentOS, etc. Oracle is looking to use Ksplice to bolster its Oracle Linux operating system and to make Oracle Ksplice part of their Oracle Linux Premier Support program.
From the press release, "The addition of Ksplice's technology will increase the security, reliability and availability of Oracle Linux by enabling customers to apply security updates, diagnostics patches and critical bug fixes without rebooting. Oracle believes it will be the only enterprise Linux provider that can offer zero downtime updates, and expects to make the Ksplice technology a standard feature of Oracle Linux Premier Support."
This latest Oracle acquisition is likely more bad news for Linux and open-source, unless you happen to be an Oracle Linux customer.