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Re: Upgrading persistent overlay?

Hello Andrew,

Sorry for not having answered your other mails yet. :-(

On Sat, Sep 24, 2011 at 08:32:32AM -0400, Andrew wrote:
> Dear Klaus et al,
> One thing standing between me and using the persistent overlay feature is
> complications on upgrading.  I would very much like to store my bookmarks,
> calendar, contacts, etc., and customizations for day-to-day use from
> multiple machines.
> But how do I easily merge all the accumulated data into a new Knoppix
> version?

Actually, it's not too complicated. The overlay is mounted under
/KNOPPIX-DATA, this contains all your changes relative to the current
read-only image.

Everything in /KNOPPIX-DATA/home is "personal settings", which you can keep.
Everything in /KNOPPIX-DATA/etc is "global settings", which is in most cases also OK to keep.

Things in /KNOPPIX-DATA/{bin,bin,usr,var,boot} are more complicated to
handle, these are changes made by additionally installed packages, which
will shadow other files when upgrading the read-only image. So, if you
installed a nes Samba version, the system booted with the new read-only
part will still see your own samba version instead of the (possibly
newer one) in the overlay.


A) If you have only modified your personal and some global settings, and
did not install any new packages, you can just copy over your
KNOPPIX/knoppix-data.img from the old version to a freshly installed USB
drive, and should be ready to go.

B) If you installed new packages or directly modified files in /usr,
/lib, ..., you have the option of keeping your changes and hoping for
the best, or you delete everything in /KNOPPIX-DATA/ except for home and
etc to start with the new, unchanged system, yet keeping your settings
from the previous one. I should probably automatize this.

> Simply copying /mnt-system/KNOPPIX/knoppix-data.aes to the new KNOPPIX
                 knoppix-data.aes is the encrypted version.

> directory will not work.  The first problem that comes to mind is that the
> old debian package database will not be correct for the packages in the
> new /UNIONFS.  Next, there will be a number of files in /etc, /root,
> /home/knoppix, and elsewhere which will not contain new configuration
> keys, and be otherwise less than 100% compatible with new packages in the
> new /KNOPPIX.

/home/knoppix should be OK, while some files in /etc may indeed not
match newer package versions.

> I booted this system live an hour ago and find there are already 350 files
> in /ramdisk.  How many files would be in /KNOPPIX-DATA after a few months
> of usage?

Some of these files are just metadata which tell aufs that file
modification times have changed, or files were removed. I don't think
that the number of files will increase much after the first few reboots,
unless you install new packages.

> How could I possibly save my data?

I would go with the option of just keeping /KNOPPIX-DATA/home and

You could first copy over the entire knoppix-data.aes, then boot into
runlevel 2, delete everything in /KNOPPIX-DATA/ except for home and etc,
and then reboot. This is what I usually do.


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