Re: Raid failing, which command to remove the bad drive?

[Bill Davidsen <davidsen@tmr.com>]

Simon Matthews wrote:
> On Sat, Sep 3, 2011 at 10:03 AM, Simon Matthews
> <simon.d.matthews@gmail.com>  wrote:
>    
>> On Sat, Sep 3, 2011 at 5:17 AM, Robin Hill<robin@robinhill.me.uk>  wrote:
>>      
>>> On Sat Sep 03, 2011 at 04:35:39 -0700, Simon Matthews wrote:
>>>
>>>        
>>>> On Fri, Sep 2, 2011 at 8:42 AM, Timothy D. Lenz<tlenz@vorgon.com>  wrote:
>>>>          
>>>>>            
>>>>>> How did you install Grub on the second drive? I have seen some
>>>>>> instructions on the web that would not allow the system to boot if the
>>>>>> first drive failed or was removed.
>>>>>>
>>>>>>              
>>>>>
>>>>> I think this is how I did it, at least it is what I had in my notes:
>>>>>
>>>>> grub-install /dev/sda&&  grub-install /dev/sdb
>>>>>
>>>>> And this is from my notes also. It was from an IRC chat. Don't know if it
>>>>> was the raid channel or the grub channel:
>>>>>
>>>>> [14:02]<Jordan_U>  Vorg: No. First, what is the output of grub-install
>>>>> --version?
>>>>> [14:02]<Vorg>    (GNU GRUB 1.98~20100115-1)
>>>>> [14:04]<Jordan_U>  Vorg: Ok, then run "grub-install /dev/sda&&  grub-install
>>>>> /dev/sdb" (where sda and sdb are the members of the array)
>>>>>
>>>>>            
>>>> Which is exactly my point. You installed grub on /dev/sdb such that it
>>>> would  boot off /dev/sdb. But if /dev/sda has failed, on reboot, the
>>>> hard drive that was /dev/sdb is now /dev/sda, but Grub is still
>>>> looking for its files on the non-existent /dev/sdb.
>>>>
>>>>          
>>> The way I do it is to run grub, then for each drive do:
>>>     device (hd0) /dev/sdX
>>>     root (hd0,0)
>>>     setup (hd0)
>>>
>>> That should set up each drive to boot up as the first drive.
>>>
>>>        
>> How about (after installing grub on /dev/sda):
>> dd if=/dev/sda of=/dev/sdb bs=466 count=1
>>      
> ooops, that should be bs=446, NOT bs=466
>    

Which is why you use grub commands, because a typo can wipe out your 
drive. May or may not have in this case, but there's no reason to do 
stuff like that.

-- 
Bill Davidsen<davidsen@tmr.com>
   We are not out of the woods yet, but we know the direction and have
taken the first step. The steps are many, but finite in number, and if
we persevere we will reach our destination.  -me, 2010