Can I Rebuild / and /usr Remotely? Ideas?

Jerry McAllister jerrymc at clunix.cl.msu.edu
Tue Sep 20 10:20:36 PDT 2005


> 
> I have a system running 5.4-STABLE.  I created a geom_stripe disk for 
> /usr.  It works fine except that upon reboot, the stripe attempts to 
> load itself twice and thus fails.  Therefore, since I have no /usr, the 
> system comes up in single user mode.  At that point I can do 'kldunload 
> geom_stripe' and then 'kldload geom_stripe' to get the stripe built and 
> finish booting my system.  I sent a problem report describing this 
> behavior.  http://www.freebsd.org/cgi/query-pr.cgi?pr=83521  Please see 
> it for details.
> 
> Based upon the information in the pr, the commiter suggests clearing all 
> metadata on the stripe providers and starting over.
> 
> 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.

> I have remote console access to this machine and want to attempt to 
> rebuild the system remotely.  If I mess up, it's not too difficult to 
> physically get to the box but I would like to avoid it if possible.  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'.   

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. 

////jerry

> 
> I'd appreciate any help or suggestions on the best way to accomplish 
> this task.  I would also appreciate any second opinions regarding other 
> ways to get geom_stripe working properly on this box.
> 
> Thanks,
> 
> Drew
> 
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