[CentOS] Re: Please help! boot problem

Mon May 1 19:38:01 UTC 2006
Scott Silva <ssilva at sgvwater.com>

Mace Eliason spake the following on 5/1/2006 1:27 PM:
> 
> 
> 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.
>>
>>   
Then the other drives partition table has been changed. You will need to have
both drives in to repair the system. If you just want to get booting, you can
swap the drives scsi id's so the good drive is the lower numbered drive. Then
you can use the rescue disk to get the system running.
After you boot with both drives in with the rescue cd, try the option to look
for linux systems. Make sure that you see both drives, and lets see the
partition info from both, again just to be safe.
I don't want to give you some commands that will cause damage.


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