thx folks for making this thread so popular...
TobiSGD: thx, i tried that using "mount -l", however the output didnt list my target partition (sda2 in my case). Only "/rootfs on /", but thats the livecd i guess.
archtoad6: yes i intend to install sabayon, thats why im using a sabayon livecd. if i fooled someone im very sorry for that.
druuna: thx for the link. but as far as i can see the tutorial is not using compress or ssd option at any point. however compress,ssd is what im after.
I feel i have to clarify my problem:
i would like to install sabayon. my root partition (except boot) should be on a btrfs filesystem. until now no problem.
here is the problem: the installer doesnt by itself allow to mount the target partition with the btrfs option "compress,ssd". only after install has completed i can edit fstab to add compress,ssd. but then its too late since most of the files have already been written uncompressed to the disk. i would have to wait a long time until every package has been updated.
so my idea was to find a way to mount the target partition using compress,ssd even BEFORE i install the whole system (still sabayon). for that, one possibility is to "remount" the partition after it has been created, but before the files are written to it by the sabayon installer. im looking for the one command line that can do this. just a "simple" remount (using sabayon).
thx for reading this far and this long.