[RHEL] booting 2+Tb disk with GPT in el6

[Joshua Daniel Franklin (UW Seattle)]

Possibly interesting info, it's now fairly easy to boot off of 2Tb+ 
drives in Red Hat EL6, though getting it to work is not obvious. For 
example, if you do a default Red Hat EL6 install on a 64-bit Dell 
PowerEdge server you will get an MSDOS disk label.

The secret is that the disk label must be GPT (GUID Partition Table) 
which is not the default for BIOS-based x86 machines (Macs and Itanium 
use EFI/GPT). Once a GPT disk label exists the installer will use it. 
I'm not clear on precisely what's going on with grub, the MBR, etc but 
it works. I did find a utility "gdisk" aka "GPT fdisk" 
http://www.rodsbooks.com/gdisk/ which has lots of details about GPT.

Here are two ways to install with GPT as disk label on Red Hat EL6:

1. In the graphical installer, before partitioning switch to a shell 
(Ctrl-Alt-F2) and run "parted /dev/sda" and "mklabel gpt". You can now 
proceed as normal in the install, including automated or customized 
partitioning, LVM, etc.

2. Using kickstart, make sure you don't use "zerombr" or "clearpart 
--all" which recreate an MSDOS disk label ("clearpart --linux" is fine) 
and add something like this (the "dd" is only really necessary if you 
need to destroy an old disk label first):

%pre
dd if=/dev/urandom of=/dev/sda bs=512 count=64
parted -s /dev/sda mklabel gpt


Unfortunately I did not have any luck getting GPT booting to work with 
Ubuntu 10.04, but I didn't try very hard. The installer seemed to always 
create a MSDOS label, and  "parted" is not available on the Ubuntu 10.04 
installer's shell, only "fdisk". Surely that will change soon with 
single 3Tb disks already on newegg, though perhaps EFI will become 
mainstream first. 2Tb disk limits are just one of many things like 
32-bit Windows that I thought would be long gone by 2011.


Some other random el6 notes:

* ISOs for 6.1 available from https://www.washington.edu/uware/rhel/

* if you want to boot the el6 installer using USB, you have to make your 
own diskboot.img using a new enough syslinux (like another el6 machine). 
Details at the bottom of 
http://trac.biostr.washington.edu/trac/wiki/KickStart

* a bunch of the package group names have changed since el5 so you're 
best using "yum grouplist", system-config-kickstart, or looking at the 
comps which are now on the installer at places like 
repodata/00fa55cde0056779ce3cb404c5097825124da4bae5823734c9978798d64428bb-comps-rhel6-Server.xml.gz

* rpm format has changed slightly so if you want to extract files you'll 
need to use el6 (or newish Fedora)

* NetworkManager
If you install NetworkManager, you may want to change this new line to 
"no" in /etc/sysconfig/network-scripts/ifcfg-eth0
NM_CONTROLLED="yes"

* LDAP
new nss-pam-ldapd means config files are now /etc/pam_ldap.conf and 
/etc/nslcd.conf

* el6 still uses grub-0.97 (Ubuntu is using the much different grub2)