I have a problem. I have 2 Sata HDD's, I can boot Ubuntu, bet it can't see my other hdd. When i boot Grub it shows Mac OS (other hdd).
What's the problem?
In what way can't Ubuntu 'see' your drive? You don't see it in your filesystem, or you can't find it using sudo fdisk -l?
It sounds to me like the drive needs to be mounted.
See how the drive is called, i.e. /dev/sda1 for the partition you want to mount.
If fdisk cannot see it, something else is going wrong. (which seems unlikely, since as noted above, Ubuntu should be able to read the HFS file system)
Ubuntu has (as far as I know) support for the OSX filesystem, HFS+. Try disabling Journaling;
Check out the full article to get around the permission problems.