I am working on the unattended-iso project, and seeing this message:
for the bots and search engines
The installer has detected that the following disks have mounted partitions: /dev/sda Do you want the installer to try to unmount the partitions on these disks before continuing? If you leave them mounted, you will not be able to create, delete, or resize partitions on these disks, but you may be able to install to existing partitions there. Unmount partitions that are in use?
It happens whenever you already have a filesystem on say sda1. Workaround:
d-i preseed/early_command string umount /media || true
