Lapohos Tibor wrote:

[...]

quoted

grub-install --root-directory=/root/os /dev/md0

and I got a warning and an error message: "Your embedding area is
unusually small.  core.img won't fit in it." and "Embedding is not
possible, but this is required when the root device is on a RAID array or
LVM volume."

What did I do wrong, and how do I fix it? Thanks ahead,

Grub2 needs a space of about 55 sectors free after the MBR. It ussually is 
63 sectors. What's the output of:
	fdisk -lu /dev/sda
the start of the first partition should be 63 sectors or bigger to leave 
enough space for grub2 to be embedded.

However, the way you are making partitions is quite complex and the needed 
space could be somewhere else.

Please, stop repeating your question everywhere.

-- 
Antonio Perez