Boot Loader on Mirrored Boot Device

[chrism]

I was setting up a mirrored boot device (per http://doc.freenas.org/11/system.html#mirroring-the-boot-device) after I had a single USB device die and fail to boot. The previous and new device was setup to boot in Legacy (Non-EFI) mode.

I added a second (to be mirrored) device, and set it to mirror in the GUI. I can see the stripes now being mirrored. Yay!

However, when I go into the BIOS to see if there is a second bootable device, I only see the original device. I would expect to see both devices and be able to boot from either of them.

My primary question is: Is the GRUB bootloader mirrored in this process as well?

I know based on the documentation that it is stated to be a second, backup "boot device", but if there is no boot-loader, it is essentially a configuration backup (valuable, but not 100% of the expectation). If in fact the boot-loader isn't installed on the second disk, is there a procedure to do so?

Otherwise, would a "dd if=/dev/<device with bootloader> of=/dev/<device with out bootloader> bs=440 count=1" be an easy fix?

Thanks in advance for your time and knowledge,
Chris

 

[Chris Moore]

I was setting up a mirrored boot device (per http://doc.freenas.org/11/system.html#mirroring-the-boot-device) after I had a single USB device die and fail to boot. The previous and new device was setup to boot in Legacy (Non-EFI) mode.

I added a second (to be mirrored) device, and set it to mirror in the GUI. I can see the stripes now being mirrored. Yay!

However, when I go into the BIOS to see if there is a second bootable device, I only see the original device. I would expect to see both devices and be able to boot from either of them.

My primary question is: Is the GRUB bootloader mirrored in this process as well?

I know based on the documentation that it is stated to be a second, backup "boot device", but if there is no boot-loader, it is essentially a configuration backup (valuable, but not 100% of the expectation). If in fact the boot-loader isn't installed on the second disk, is there a procedure to do so?

Otherwise, would a "dd if=/dev/<device with bootloader> of=/dev/<device with out bootloader> bs=440 count=1" be an easy fix?

Thanks in advance for your time and knowledge,
Chris

There may be something that needs to be configured in your BIOS / UEFI firmware, but both devices should be equally bootable. I have tested that on my system (by removing one of the devices and rebooting) and it will boot from either device. You can test it for yourself with just a couple of reboots.

 

[Ericloewe]

Way back in the day, this was somewhat broken and some scenarios only installed the bootloader on one device. That was fixed quite some time ago.

 

[David Steinberger]

I just tried it myself. I had a single USB device and added a mirror via the UI. When i then reboot with just the new USB stick I get a Grub error (something like "no such device: ..."). Booting from the other USB device works just fine.

 

[Ericloewe]

Well, the exact error would be useful to know.