How to install UCS without writing partition table

I am trying to test UCS community on a machine that is not able to boot from a GPT formatted hard disk, so I have to use MBR.
As long as UCS will be installed with other test systems, I will have to put it on an extended partition.
It happens that, for something very odd, UCS installation program is not able to recognize, in the properly way, my hard disk, while other linux distros (Slackware, Ubuntu for instance) do.
Simply the system, after I tried the expert or MBR installation mode, stops after trying to write the partition table, claiming it is not able to do that.
I tried to pre-prepare the extended partition using gparted, hoping that UCS installator will be able to just write in its data, but no way: always the program tries to write the partition table, so ending always in error.
Maybe I forget something, but is there a way to just write UCS installaton data in some partition without writing again the partition table?
Thank you all for any help


did you try to define the desired (and prepared) partition layout with UCR vars as described in Extended installation documentation - Expert mode for the partitioning in Univention Installer and Software-RAID?

Best Regards,

thank you. Now it is installing, without trying to write the partition table. Just keeping my fingers crossed.
Following your advice I manually set my partitions I prepared before starting the UCS installer (fdisk and cfdisk commands had the same error problem I encounter while just using the installer as is).
Thank you for your help.
Best Regards