The files in this directory are useful for booting a machine via PXE.  

The following files are available:
vmlinuz - the BOOT kernel used for the installer
initrd.img - an initrd with support for all install methods and
    drivers supported for installation of Scientific Linux (Fermi)

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In order for Scientific Linux Fermi to find the right install image you need
to make a small change to your tftp server config file.

You need to add to the "append" line in

/tftpboot/linux-install/pxelinux.cfg/default

or your customized "default" file

site=Fermi

So what used to look something like

  label 1

     kernel /someplace/vmlinuz
     append initrd=/someplace/initrd.img ramdisk_size=10000

now should look like

  label 1

     kernel /someplace/vmlinuz
     append initrd=/someplace/initrd.img ramdisk_size=10000 site=Fermi