Cloning, used to be: Re: deleting firefox 10.02 from kpackagekit in k10.10 mm

[Waleed Hamra]

On 22/05/12 19:00, Perry wrote:
> 
> Ray wrote:
> [snip]
> 
> Well, I expected some tips on this "cloning".
> _Whiping everything clean before using the backup would surely work
> but is quite drastic. 
> _Of c ourse you could leave untouched your personal documents,
> photos, and so on ; it's better not to delete and restore them.
> _I fear (not sure) that just overwriting with the backup-files may cause problems,
> for instance if a new app uses an existing config file.
> 

well it depends on what is being backed up.
for anything under /home, cloning isn't really the best of options.
plain old fashioned backups are easier to use, as they allow you to
restore files, while keeping any new files you've created after the last
backup. and generally, there's negligible harm from keeping these new files.
but for the root partition, assuming your /home is on a different
partition, restoring backups on top of the partition will royally mess
up your dpkg system. this is a case for cloning. the way cloning works,
the entire partition is, along with its structure is saved (backed up).
and unless you're using some specialized smart cloning manager,
restoring without wiping is impossible (and most certainly
unrecomm-ended). you see, dpkg keeps a database of every file installed
by every package you install, not to mention their configuration files,
their installation states, their dependency information, etc... this is
the very heart of debian and debian-based systems. adding files from new
packages, without having dpkg aware of them, is a recipe to chaos.
now in the case you are using same partition for / and /home, you have a
bit more work. you should be using normal archive backups for your home
directory, and storing them away, and a clone of your / (which will
inadvertently include /home) once every while. if things get messed up,
you recover from the clone (which will also mean your /home got
recovered), and then restore from the newest /home backup (assuming it's
newer than the used clone).
personally, i never saw the need for / backups at all. the beauty of
debian based systems is how you can perform all sorts of repairs using
the package manager. with your system files modified only during package
installs/upgrades/removes, it's very rare to have filesystem corruption
resulting from power loss or a hang, and if that happens, reinstalling
the package with corrupt files resolves the problem. if a package causes
conflicts or problems, it's as simple as removing it to fix the system.
if a particular version is problematic, pinning the package works, etc..
etc..
i hope this was helpful :)

-- 
Waleed K. Hamra
Manager of Hamra Information Systems



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