While trying to transfer your system to another drive:

tar -cpf - /olddisk/* | tar -C /newdisk -xf -

Have fun.

What went wrong apart from what can be fixed by cd /newdisk/olddisk; mv * ..; cd ..; rmdir olddisk?

Never using tar for that... I prefer rsync -xvaSHP /olddisk/. /newdisk

Everything got overwritten by itself, but resulting files that contain no data. All of init scripts, the whole boot directory, everything.
I only hope ~ hasn't got damaged, so I can restore my settings.

that rsync command looks really good, making a note of it

but can that be used for roots? e.g. will it ignore proc dev sys

rsync has a feature to ignore certain elements given in a file

btw, when booting the system from a live-cd for this matter (might be a very good idea) there should be nothing at least in /sys, /proc - and what exists in /dev is needed to be there

C.Brutail wrote:Everything got overwritten by itself, but resulting files that contain no data. All of init scripts, the whole boot directory, everything.
I only hope ~ hasn't got damaged, so I can restore my settings.

Why? Does tar do such things because /olddisk/ is an absolute path? I didn't expect tar x to be THAT bad... wouldn't that be a security hole when extracting tarballs from the internet? Or did /newdisk maybe not exist yet?

tar --help:

-f, --file=ARCHIV Archivdatei oder Gerät ARCHIV benutzen

or in english:

-f, --file=ARCHIV use archiv file or device ARCHIV

perhaps that was the problem - you did not use a file, but a pipe (stdout - stdin)