Danube Cloud v4.2 and later supports hybrid boot from USB and from a disk. That means you can boot the legacy BIOS way or UEFI way without any modifications. Just change your boot settings in BIOS.

If you are installing a new compute node using v4.2 or higher, you don’t have to do anything. By upgrading a platform from previous versions using esdc-platform-upgrade, USB boot will automatically receive UEFI support. However platform upgrade of disk install will not create EFI partitions because it would require destroying the zones pool.

Disk UEFI Boot And Replacing Disks

UEFI boot requires at least one EFI partition. Installer creates EFI partitions on every disk in zones pool. This ensures that you will be able to boot from disk (when disk install is selected) even after disk(s) failure/replacement. Furthermore, esdc-platform-upgrade always checks the EFI partitions and reinstalls them as needed (even if the platform upgrade is not neccesary).

If you replace any disk, the appropriate EFI partitions will be reinstalled on next run of esdc-platform-upgrade.

If you want to reinstall EFI partitions without platform upgrade, just run esdc-platform-upgrade with the current platform version, e.g. esdc-platform-upgrade $(uname -v|sed 's/esdc_//').