Rebootless Updates

In earlier versions of Parallels Server Bare Metal, applying updates to your system often required rebooting the server. During reboot, all virtual machines and Containers running on the server were shut down and started again. If the number of running virtual machines and Containers was high enough, stopping and starting each of them could result in significant downtime.

Starting with version 6.0, Virtuozzo supports rebootless updates. During such an update, all running virtual machines and Containers are suspended in the server's memory and then resumed rather than shut down and started again. This greatly reduces their downtime and virtually eliminates service outage or interruption for end users.

To perform a rebootless update:

1. Download and install the new Virtuozzo kernel using yum. For detailed information on updating kernels, see Updating Kernel.
2. Run the vzreboot command:

   # vzreboot

   This command checks the GRUB configuration file to determine the default kernel, loads this kernel into memory, and then boots the new kernel. You can also specify the kernel version manually, for example:

   # vzreboot 2.6.32-042stab054.2

   In this case, the command will load and then boot the specified kernel instead of the one set as default in the GRUB configuration file.

Note: Updating certain components of Virtuozzo may involve automatic update of guest tools in Windows-based virtual machines, which may lead to their additional downtime. To avoid such downtime, you can disable automatic update of guest tools with the prlctl set --tools-autoupdate off command.