[CentOS] Re: Please help! boot problem

Mace Eliason meliason at shaw.ca
Mon May 1 20:27:17 UTC 2006



Scott Silva wrote:
> Mace Eliason spake the following on 5/1/2006 12:55 PM:
>   
>> Scott Silva wrote:
>>     
>>> Mace Eliason spake the following on 5/1/2006 12:29 PM:
>>>  
>>>       
>>>> Scott Silva wrote:
>>>>    
>>>>         
>>>>> Mace Eliason spake the following on 5/1/2006 12:13 PM:
>>>>>  
>>>>>      
>>>>>           
>>>>>> So from what I have read I would run grub-install /dev/sda ?
>>>>>>
>>>>>> I have setup the raid with
>>>>>> /boot (100Meg)
>>>>>> /swap (2gig)
>>>>>> / (the rest)
>>>>>>
>>>>>> All 3 are mirrored.
>>>>>>
>>>>>> I don't want to mess this up sorry I am new to this.
>>>>>>
>>>>>> Mace
>>>>>>
>>>>>> Scott Silva wrote:
>>>>>>           
>>>>>>             
>>>>>>> Mace Eliason spake the following on 5/1/2006 10:58 AM:
>>>>>>>  
>>>>>>>               
>>>>>>>               
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I have a setup with raid 1 and one drive has failed, and the other
>>>>>>>> drive
>>>>>>>> won't boot says missing os.
>>>>>>>>
>>>>>>>> I thought I had it setup and tested but it would appear that it
>>>>>>>> wasn't
>>>>>>>> setup to boot form either drive.
>>>>>>>>
>>>>>>>> How can I boot from the good drive that is missing the grub.
>>>>>>>>
>>>>>>>> I am thinking of using linux rescue when booting from the centos 4.2
>>>>>>>> disc
>>>>>>>>
>>>>>>>> This is a production machine and I don't want to mess it up.
>>>>>>>>
>>>>>>>> Please help
>>>>>>>>                         
>>>>>>>>                 
>>>>>>> Use linux rescue and you can fix grub.
>>>>>>> http://www.gnu.org/software/grub/manual/html_node/Invoking-grub-install.html
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>  
>>>>>>>                 
>>>>>>>               
>>>>> less /boot/grub/grub.conf and post please-- just to be careful.
>>>>>
>>>>> Okay I have booted with linux rescue and skiped the network setup, and
>>>>> skiped the next part and gone right to the shell.
>>>>>         
>>>>>           
>>>> If I type grub-install it says no such file or directory.
>>>>
>>>> I tried less /boot/grub/grub.conf same thing.
>>>>
>>>> I did boot with the centos cd as if I was installing and used manual
>>>> partion to see if the partions where still there and they are.
>>>>
>>>> No sure what to do now.  I will try and search for  grub-install.  I am
>>>> assuming that I am searching the cd?
>>>>
>>>> Mace
>>>>     
>>>>         
>>> You can't skip the part about mounting your existing system. You will
>>> need to
>>> do that, and after it mounts, run chroot /mnt/sysconfig.
>>> That should make all the commands run on YOUR files instead of the
>>> bootdisks
>>> running system.
>>>
>>>   
>>>       
>> Okay I didn't skip this time and it did a search and says "You don't
>> have any Linux partitions. Press return to get a shell. The system will
>> reboot automatically when you exit from the shell."
>>
>> What the?
>>
>> If I goto the shell and run fsdisk /dev/sda it shows I have 3 partitions
>> with /boot set for booting.
>>
>> I do get that?
>>     
> If you show a /boot partition you don't have software raid.
> The partitions in software raid are type fd (linux raid).
> Does the replaced drive show up?
>
> With a scsi drive, the lowest number addressed drive in the chain will be sda.
> So if you had an sda set as device id 0, and an sdb set as device id 1, and
> removed the sda drive, what was sdb would now show up as sda. Scsi doesn't
> have fixed addresses like ide.
> If you had proper software raid, your partitons would be all of typd fd, and
> you should have a matching set on each drive ( sda1 and sdb1 would both be
> type fd and the same size ,etc...).
>   
Okay to clarify

I have only hooked up the drive that is not bootable.  The drive that is 
bootable has been disconnected.

If I run sfdisk on the nonbootable drive I get
/dev/sda1  (id fd linux raid autodetect) marked * for boot
/dev/sda2   "   "
/dev/sda3   "   "

So yes it is software raid am I right.  The system has been running off 
this drive for almost a month, until someone rebooted the server.

Should I have both drives installed when I run the linux rescue?  I know 
the one drive will boot now that I fixed it but the info on it is amost 
a month old.  I really need the info from the drive that is not 
bootable.  Last time I tried to boot with both drives installed it 
didn't it gave a no boot partition error.

Does linux automatically rebuild the raid when it boot?  If I do get 
them to boot with the good drive I don't want it to over write the 
current drive.

Thanks  you have been alot of help so far. 
>
>   



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