Installing CentOS 6.x From USB
If at all possible, don’t do it. Find a blank DVD-RW and burn the ISO file. Most current Linux distros can be easily put on a USB stick using freely-available utilities and installed without a hassle. CentOS is not one of them. It would appear, CentOS was designed specifically to make installation from a USB stick a professional challenge for a seasoned sysadmin.
But, if your time is free and you still want to give the USB route a shot, here are a few suggestions.
Most system boards no more than a few years old support booting from USB. You will need to go into the BIOS settings to make sure USB in on the boot list. If USB does not appear among the bootable devices in BIOS, try hitting F8 after the initial system board splash screen. Older system boards would display a boot device selection menu.
As of today (2014-01-15), the latest and greatest version of CentOS is 6.5. Don’t use it: it’s full of bugs. Go for 6.2. This is just a personal opinion that will likely save you a lot of time and brain cells. Lately, it feels like a bunch of monkeys with computers got a hold of CentOS source code.
For example, if you try to install CentOS 6.5 from the full 4-GB “DVD1” ISO, the installer will attempt to connect to the online repo for no reason at all. If, at the time of installation, your system has no network connection (as would normally be the case), the install process will fail. Someone on the CentOS dev team needs a good kick in the butt.
I’m glad you asked. Don’t bother with the standard DVD image. Get the LiveDVD image instead. It will be called something like “CentOS-6.2-x86_64-LiveDVD.iso”. Another advantage: the LiveDVD image is 1.7 GB vs 4.16 GB for the full DVD ISO.
How to ISO-to-USB
If your base of operations is a Windows laptop, your CLI is useless. You will need to get the right ISO-to-USB conversion utility. There are many to choose from and they are free, but most suck and will not work with CentOS ISO.
I recommend the “Universal USB Installer” (Google the download link). But there’s a little trick to using it: in “Step 1”, select Other à CentOS; in “Step 2” click “Browse”, navigate to the folder containing the ISO and in the “File name” enter “*.*” and then you’ll be able to select the ISO file. A strange way of going about it, but what are you gonna do?
You will need at least a 4-GB USB stick. An 8-GB stick is recommended. Plug it in your Windows PC; open Windows Explorer; right-click on the USB drive letter and click “Format”; select FAT32 and do a “quick format”. At this point I should probably mention that all data on your USB stick will be deleted. Also, take care to format the right drive and not your C: drive, ‘cause that will be a bummer.
Booting and Installing
Boot from the USB stick into CentOS Live. You will see a desktop with the “Install to Hard Drive” icon. Follow the usual CentOS installation prompts. When the system reboots (don’t forget to pull the USB stick out), complete configuration and set up network. Once you have network connectivity, you can install whatever other pieces you need.
CentOS is my third most favorite distro after SLES and RHEL. It’s a shame what they did to it. “Test before production” is all I can say.