The scenario:
- Acer Altos server with legacy LSI MEGARAID onboard card
- only one previous HD left, so I basically don't need RAID anymore
The problems are 3:
- the BIOS settings, to be setup from RAID to ACPI
- the RAID configurations left on the HD from previous installations
- Ubuntu actually do recognizes the card even if disabled and refuses to use ACPI configuration
I solved this way:
- BIOS settings in Advanced / IDE configuration: disabled everything and enabled legacy support (it eats 2 SATA ports but I dont think it's mandatory... however I don't need them)
- from Ubuntu netinstall 16.04 I launched the command line (there's the option during the installation when the bootloader fails or you exit partitioning or choose safe mode at the beginning) and gave these command:
- take note of "124914352 sectors" and give
- Now proceed to install CentOS 7, because Ubuntu will keep recognizing the RAID onboard card and refuses to use ACPI configuration
- # dmraid -r
- /dev/sdb: ddf1, ".ddf1_disks", GROUP, ok, 124914352 sectors, data@ 0
- # mdadm --zero-superblock /dev/sdb
- and then try again # dmraid -r
- it should reply with no raid disks and with names: "/dev/sdb"
- If the first gave error, get the sectors you noted before and give
- # dd if=/dev/zero of=/dev/sdb bs=512 seek=124914352
- and then try again # dmraid -r
