Can I Rebuild / and /usr Remotely? Ideas?

Drew Tomlinson drew at mykitchentable.net
Tue Sep 20 14:43:32 PDT 2005


On 9/20/2005 11:28 AM Jerry McAllister wrote:

>>On 9/20/2005 10:20 AM Jerry McAllister wrote:
>>
>>    
>>
>>>>When I built this system, I configured the disks using sysinstall.  I 
>>>>used the "dangerously dedicated"mode just as I had when I ran the 4.x 
>>>>series.  I suspect my problems occur because geom_stripe doesn't get 
>>>>along well with disks that are "dangerously dedicated". 
>>>>
>>>>Anyway, my system has 2 9gb drives (da0 and da1) that I wish to use for 
>>>>the main system.   I want a 500mb slice as /dev/da0s1a for '/', a 500mb 
>>>>slice as /dev/da1s1b for swap, and the rest of each drive as 
>>>>/dev/daXs1d.  I will build my stripe with /dev/da0s1d and /dev/da1s1d 
>>>>and mount it at /usr.  Other directories such as /var, /home, etc. will 
>>>>be symlinked to /usr/var, /usr/home, etc.
>>>>        
>>>>
>>>I would be inclined to want some swap on da0 - the boot drive - too, but
>>>I guess you don't have too.
>>>
>>>      
>>>
>>What would the advantage be?  My thinking is to put root on one and the 
>>same size swap on the other leaving two equal sized partitions (or are 
>>they slices? I'll never get that straight) with which to build my stripe 
>>set.
>>    
>>
>
>Just always the feeling that I should be adequately functional at least
>to be able to work on fixing things with only one drive available.
>Actually, I would put swap on both  da0s1b = 500MB and da1s1b = 1GB.
>  
>

OK, thanks for that explanation.

>>>>I have another disk on the system (ad0) that is available and large enough 
>>>>to hold the contents of both da0 and da1.  Can I backup my system, do 
>>>>the needed operations on da0 and da1, restore da0 and da1, reboot, and 
>>>>still have a working system?  I've never used fdisk, bsdlabel, newfs, 
>>>>and whatever else I might need from the command line.  Besides the man 
>>>>pages, are there any guides for what I want to do?  Even a simple "first 
>>>>this, then this, then this" type of guide will help me get started.
>>>>        
>>>>
>>>As long as there is room on the ad0 drive for all of the dumps there
>>>should be no problem.    There will be a dump file for each current
>>>file system.   You may also need to have some space to unroll a dump
>>>if the way you are breaking up the file system in to parts with links
>>>is different than the way it is now.   for example if you take /usr/local
>>>out our /usr and put it in its own space, you will first need to restore
>>>all of /usr somewhere (maybe in its new space if there is room or on
>>>the ad0 drive if there is not) and then transfer the separate parts to
>>>their new homes - probably using 'tar -cpf'.
>>>      
>>>
>>I'm happy with the layout now but needing intervention on each reboot is 
>>not acceptable to me.   This is the only reason I'm considering this 
>>exercise.
>>
>>    
>>
>>>The main thing is to think out the pieces - what each file system is and 
>>>what order you will need to restore things so the each new file system 
>>>is created and ready and the mount points are there when you need them. 
>>> 
>>>
>>>      
>>>
>>Thank you for your reply.  This gives me some direction in which to 
>>proceed.  Since the layout is as I like now, it seems to me that I would 
>>only have to dump / and then dump /usr.  The restore order would be 
>>first / then /usr.  Is that correct?  Here's my current fstab:
>>    
>>
>
>Sounds right from what you indicate here.
>  
>
Wait a minute.  I just thought of something.  I am not going to be able 
to work on da0 while it's mounted, correct?  and since da0s1a is my root 
partition, I'm not going to be able to unmount it until I boot from 
another disk, presumably ad0.  How do I set up ad0 so it will boot?  
Then after making a complete copy of / and /usr on ad0, I will have to 
boot from it before doing my work on da0 and da1.  At that point I'll 
have to do the secret incantations of fdisk and bsdlabel on da0  and 
da1, build my stripe, mount everything, use dump/restore to copy the 
contents of ad0 to it's respective places, and then finally reboot from 
da0.  Uh oh, I think this is getting complicated...  :)

Thanks,

Drew

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