Tricks with PXE

Normally, the initramfs will load up, load a network driver, and attempt to contact a DHCP server to configure itself. However, on many modern systems, the PXE boot mechanism is already contacting DHCP and receiving IP information. This makes the DHCP step that runs from the oneSIS initramfs somewhat redundant. If you are interested in shaving some time off of your boot, or if for some reason you cannot run DHCP over your boot interface (as with boot over Infiniband (section 3.3.3)), oneSIS can use the IP information supplied via DHCP in the PXE phase of the boot. Note that it is necessary to use the 'root=' kernel parameter to specify an NFS root as this data is not sent via DHCP in PXE. Also the host name must be set by one of the methods in section 5.11, such as an entry in /etc/hosts.

Procedure 5   Enable the initramfs to use IP information from PXE

 $\bullet$ Add 'ipappend 3' and 'root=' to your pxelinux configuration file:

label initramfs

kernel vmlinuz-3.10.0

append	initrd=initramfs-3.10.0console=ttyS0,115200
	root=10.20.10.20:/var/lib/oneSIS/images/RedHat-EL-5.1,tcp,hard

ipappend 3

 $\bullet$ Tell mk-initramfs-oneSIS not to run DHCP

mk-initramfs-oneSIS	-nodhcp /tftpboot/$<$initramfs-img$>$
	$<$kernel-version$>$ $[$OTHER_OPTIONS$]$