Can't get ProxMox to boot on Legacy BIOS.

Justarico

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Feb 13, 2025
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> Heya everyone, obligatory this is my first post line here <

I'm trying my best to give a full rundown of the steps I've taken since I've received the system. Please keep in mind I'm newish to Linux and this is the first enterprise grade server I bought after hosting proxmox on an old desktop.

I bought an old Fujitsu RX300 S8 with a Fujitsu D3116C Megaraid card. As I wanted to use truenas and ZFS to install the containers and VM's to, I didn't want the D3116C to create a raid array. However, that version of the card doesn't come with IT, firmware. Finding out it was based on the LSI 2208 and knowing that can be flashed to IT mode firmware for cards based on 2308, I did so. I followed this guide with the adaptations from this forum thread of someone trying the same thing on the D3116(non-C) card. The C was just a later revision and those steps worked. My drives, two Seagate 10k RPM 600GB SAS HDD's and one Crucial 500GB Sata SSD, showed up as plain drives in the proxmox installer.

After completing the GUI Install and getting to the reboot phase and unplugging the install USB, it booted me straight back into the BIOS. I was stuck for a while and found out through lsblk, lspci, and dmesg | grep SAS. that it had properly formatted the drives into partitions. But they still weren't showing up in the boot screen, boot settings or bios settings.

I then found out that the bios/motherboard combo in this particular server doesn't support UEFI booting from PCie attached storage. And seeing as it doesn't have available plugs for sata power (the controller backboard is powered by proprietary plug), I have to install it in legacy mode. After enforcing legacy boot media with CSM settings I ran the non eufi installer, but it still wouldn't let me boot. I used the previously mentioned commands and saw it still created an EFI sba volume and used GPT instead of MBR.

It's at this stage that I'm stuck. I can't seem to get proxmox to install to legacy compatible hardware.

It's so unbelievably infuriating slowly getting further and further into the install process, only to get snagged at what feels like the final stretch. So if anyone knows what I should do, or has faced the same issue, please let me know what to do. I'm more than happy to provide console logs, command outputs, whatever is necessary to get support. I just don't know what I should already include in the post as like I said earlier, I'm newish to Linux and don't know what is, and isn't relevant.

Kind regards, and thanks for reading all this:

Rico
 
Have you selected a disk to boot from in the controller bios? Even in IT mode, this may be necessary. If it's a general problem, try to install an OS you're comfortably with in order to see if it's a PVE or a general boot problem.

Please keep in mind I'm newish to Linux and this is the first enterprise grade server I bought after hosting proxmox on an old desktop.
Your old desktop may be newer than the RX300S8, which is VERY old and IIRC with a seriens Xeon 5600 CPU. Fujitsu discontinued after the RX300S8 with the scheme and we're now 7 generations later on the RX2540M7.
 
Hey, thanks for the reply! I had not checked if it was selected as a boot drive in the controller bios, only the motherboard. Luckily, the drive was automatically selected as boot media in the drive controller. Ubuntu and Windows 10 did install using legacy mode, only the proxmox installer and Debian refused to play ball. I think the issue was with the motherboard enforcing legacy bios boot only for the pci-e attached storage. USB and direct sata connections can be set to uefi as well as legacy. Perhaps the installer saw uefi was one of the possible options, even after enforcing legacy in the bios, and selecting the non uefi boot entry (Sandisk, as opposed to UEFI: Sandisk) from the boot menu. Luckily after a few days of trying I managed to find a good quality molex to sata adapter (I know, molex to sata, lose your data, but for a singular SSD it should be fine). Which allowed me to boot from UEFI as it was directly connected to the motherboard using sata.

I'll happily concede that the server itself is quite old. But it's actually one year newer than my old desktop, with dual CPU's and about 10 times the amount of equal speed ram, so from that point of view, it's still a huge upgrade.

I should've probably mentioned it's for a homelab setup, and therefore isn't anything remotely close to mission critical infrastructure.

In any case many thanks for the suggestion as it was something I hadn't considered before.

Kind regards,

Rico