Nas raid server with Linux? not booting

[Zourous]

I know nothing about these things, as I was brought up on Windows.

The first disk (primary) out of four in the raid was reported bad by the smart diagnostics. I replaced the disk but it doesn't boot and gives out these three lines at the end.

VFS: Cannot open root device "md3" or unknown-block(0,0)
Please append a correct "root=" bot option
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

Ok, so I have to edit and change something to get it to work, but as a starting point how to I even do that? Do you have to use some sort of bootable USB? and what config's am I likely to need to change? I think the system is using something called LILO (v.22.6.1) if that's any help.

[mister_z]

1. Does it boot with the new disk removed ?
2. Is there a controller BIOS setup screen (Ctrl-A at boot up, for example) ?
3. Is this a "regular" server with multiple drives, software RAID, and linux loaded ? If not, what is the manufacturer ?

One thing in my experience that matches this is a system with software raid, that is trying to boot from a hard drive that was never bootstrapped. One can start up a system from drive 0. install Linux on software RAID, and think "Aha! Now I am safe!." But without loading LILO or GRUB into the boot block of the second physical hard disk, if disk 0 fails, the O/S has nothing to boot from.

Another alternative, presuming SCSI disks, is the need to set the disk controller BIOS (e.g. the Adaptec 29160 or what have you) to boot from the second SCSI ID if the first one has failed and been replaced. Otherwise, the BIOS goes to the first disk, which was replaced and has no boot block. and fails to boot.

[dhicks]

The first disk (primary) out of four in the raid was reported bad by the smart diagnostics. I replaced the disk

Are you sure you replaced the right disk? Linux doesn't neccesarily enumerate disks in the order they happen to be arranged in.

Is this a bought device, or a home-made server? If it's bought I'd be surprised if the OS was on the RAID array along with the data. If you boot the machine off SystemRescueCD, it should scan the machine for any software RAID arrays, full or partial. After that you can tell mdadm (the utility that handles arrays for you) to add the new disk to the RAID array and to start syncing data.