[CentOS] iMac triple boot including CentOS 6.4

-How to install CentOS on 27” imac (Mid 2010 - 2.93 Ghz, i7, 8gig ram)
 with OS X and Xubuntu 13.04 already installed

Assumed - OS X and Xubuntu already installed and rEFIt already installed in
OS X with the line towards the bottom of:

/efi/refit/refit.conf

set to:

default_selection L

on the mac root partition so Linux will boot by default

-Boot centos 6.4 lived dvd and install btrfs tools from installer then run
these commands to resize btrfs partition (changing size to fit your needs):

( was testing btrfs so use the resize tool for your type of file system
installed)

# mkdir /media/b

# mount /dev/sd(whatever) /media/b

# btrfs filesystem resize -900g /media/b

-Created a gparted boot disc from:

http://gparted.org/download.php

then booted from gparted Live-CD and resized partition

-Booted back into xubuntu and ran update-grub - but it didn’t find centos

-Now run upgrade from 13.04 to 13.10

ran update-grub again and now it sees Centos

run

vi /etc/default/grub.conf

change GRUB_DEFAULT to

GRUB_DEFAULT=6

run update-grub again

reboot

Now Centos will will show up in grub2 boot menu and be the default one
selected

If CentOS has a kernel change, update-grub must be run again in xubuntu.

-Update system

$ sudo yum update

reboot


---------------

Info above can be found here:

https://sites.google.com/site/comptekkia/linux/how-to-install-centos-on-mid-2010-27-imac

Thanks,

-wes