istallation from other linux

[wtq4er]

i have working gentoo and i'm trying to install ubuntu without cd and usb flash. im using ths guide https://help.ubuntu.com/community/Installation/FromLinux and i get all the time stupid message from live system that medium with live cd data not found. i also tried to use option LIVEMEDIA=/dev/sdb1 but still the same stupid error.
i made all partitions and wrote into grub.conf all needed:

title installer
root (hd0,5)
kernel /casper/vmlinuz boot=casper root=/dev/ram ramdisk_size=1048576 rw
initrd /casper/initrd.lz
live cd start booting and then sticks on looking for medium with live cd lol
i haven't yet tried to use the alternative cd.
the fact is that my pc can't boot from usb and cd rom always read with errors.
thanks for any help.

[wtq4er]

OK, note3 that recommends to

simply use the boot option live-media=/dev/sdb1 or LIVEMEDIA=/dev/sdb1, referring to the usb device holding the ISO.actually works, but you should copy to usb not ISO as it's written there but the content of ISO. Those are different things i suppose. If anyone has access to edit this (https://help.ubuntu.com/community/Installation/FromLinux) document, please correct there what i said above.
I'm writing from ubuntu live environment now. And we'll see if there would be errors during installation.

[wtq4er]

allright here's new ****. i get this:

Возникла проблема при копировании файлов на жёсткий диск:

[Errno 5] Input/output error

Это часто происходит из-за неисправности CD/DVD диска, привода, или жёсткого диска. Возможно поможет очистка CD/DVD диска, либо запись CD/DVD на более низкой скорости, либо очистка линз CD/DVD привода (соответствующие комплекты для очистки доступны в продаже), возможно жёсткий диск уже очень старый и нуждается в замене, либо необходимо переместить оборудование в более проветриваемое место.It says that i have bad CD/DVD lol. I tried both - install using flash as source of livecd contents and hdd partition as source( Yep, that is possible too, just need to put option LIVEMEDIA=/dev/sda6 in my case) - in both cases same ****. What the hech is this? corrupt iso image? or some errors when using rsync /iso-mount/ /destination-device/