working and tested USB install procedure for RH 6 based distributions (RHEL 6.x, CentOS 6.x, Oracle Linux 6.x and others)

We needed to install CentOS 6.4 machines with USB and got into absolute madness. All RHEL cones have no working procedure and workarounds consisted of using FAT32 partition with 3rd party tools (problematic with install ISO files greater than 4GB) or multiple partitions and remounts. Until we found a very simple solution that did not work as well and fixed it.

To create the USB You will need:

• Red hat based distribution to create the USB (in our case CentOS-6.4-x86_64-bin-DVD1.iso). 
• Actual CD iso image 
• Fedora livecd-iso-to-disk script

Steps are very simple:
Insert the USB stick to the port.
You need to find out the device name (for ex. /dev/sdb1 )
On systems with auto-mount just run df -h or plug it in and run dmesg | tail -20

Install livecd tools:
yum install livecd-tools

Make sure it is bootable  (for ex. /dev/sdb1, via editing it`s parent - sdb ):
/sbin/parted /dev/sdb
(parted) toggle 1 boot
(parted) quit

Format it with ext3 (does not support ext4)
mkfs.ext3 /dev/sdb1

Prepare the USB (for example using CentOS 6.4):
livecd-iso-to-disk --reset-mbr CentOS-6.4-x86_64-bin-DVD1.iso /dev/sdb1

Your USB is ready, it will boot but fail to install since it is missing install root, so we need to fix it.
Edit exlinux.conf, you will see something similar to:
append initrd=initrd.img stage2=hd:UUID=791fc126-638c-4f28-8837-f3c2eae31e57:/images/install.img repo=hd:UUID=791fc126-638c-4f28-8837-f3c2eae31e57:/

what is mising is directive "root=" so you need to switch the line to something similar to: 
append initrd=initrd.img root=UUID=2cd71b0d-09a0-47b6-97ef-02c3fa90e9d3 repo=hd:UUID=2cd71b0d-09a0-47b6-97ef-02c3fa90e9d3:/

save the file and boot fro USB. It will install your OS.

Provided by: Forthscale systems, cloud experts