[Discuss] Multiple HDD setup in Linux

[Alan W. Irwin]

On 2008-05-06 20:34-0700 Brian Burger wrote:

> Thanks for all the feedback, everyone. I'm going to do a pile of
> reading tonight, and tackle the actual installation tomorrow or
> Thursday.
>
> It looks like it's possible to mix-and-match - some non-LVM regular
> partitions and LVM partitions on the same HDDs. Assuming that's true,
> here's the plan:
>
> 1. Unplug the 120GB completely.
> 2. Plug the 500GB in, do a clean install with the Ubuntu 8.04
> Alternate install CD to set it up as follows:
> - /boot - 500MB, likely less
> - / - 30GB, not LVM'd
> - /swap - 2GB; there's 2GB of real RAM in this box, so 2 of swap is enough
> - /home - LVM'd across the remaining 475+GB of the new drive
>
> 3. After the new system & drive is up and running, mount the 120GB's
> old /home and transfer my files across with dd.
> 4. Reformat the entire 120GB; then use LVM to add that whole volume to
> the existing new /home.
>
> This keeps my old install & personal data intact on the old drive for
> as long as possible, gives me minimum likelyhood of a partitioner
> glitch eating everything, and (thanks to LVM) lets me use the old
> drive as seamlessly as possible.
>
> Sanity check, anyone? This makes sense in my own head and from my
> reading of the docs, won't be that difficult... I hope.

Everything seems fine to me in your above plan except for 3.  dd is really
low level so I am not sure you will get the intended result with it.  For
example, you might copy rather inefficient ext2 options from your old disk
to your new disk, you will probably have trouble with the numerical UID and
GID for the files, and you might have trouble with lvm for the result.  To
avoid those potential issues, I would simply use cp -a.

To check for i/o errors or other problems with such a copy I would calculate
an md5sum for every file on your old disk as follows:

find . -type f >| files.list
cat files.list |xargs md5sum >| md5sum.out

Then use that md5sum.out file to check the copied files on your new disk
using "md5sum -c md5sum.out" in the appropriate directory.

(I use this trick a lot to do a complete end-to-end check of the reliability
of every bit of every copied file when there are a large number
of such files.  This trick gives great peace of mind.)

Another possibility is to use rsync (which does have an option to check
every bit of the copy), but for one-time copies I prefer cp -a.

> It'll also give me a totally new install of Ubuntu 8.04 - I've been
> upgrading for several years now, since 5.10, so a LOT of my defaults
> aren't the newest & shiniest Ubuntu goodness...

That's quite a long and impressive track record for dist-upgrades.  However,
I agree it is a good idea to start fresh periodically since the best default
packages change over time.  In fact, I start fresh every time there is a new
Debian release, but, of course, that is not every 6 months.  :-)

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of
Linux Links project (loll.sf.net); and the Linux Brochure Project
(lbproject.sf.net).
__________________________

Linux-powered Science
__________________________