For a bootloader to be installed, a /boot directory must
be deployed on a local disk. The bootloader is installed onto the
disk containing the /boot directory. A working configuration
for the chosen bootloader is necessary (ie: in lilo.conf or
grub.conf).
It is not necessary to install a bootloader even if the entire
root filesystem is on a local disk. Any node capable of network
booting can still retrieve its kernel and initramfs from a network resource
such as DHCP and PXELINUX.
Alternatively, NFSroot nodes can create a single /boot
partition on a local disk, install a bootloader, and load the kernel
off the local disk, but still mount the root filesystem accessed via
NFS. Loading the kernel from a local disk can help reduce network
contention at boot-time when many machines power on all at once.
Many options exist to boot any node or functional group of nodes (locally or from the network) into a root filesystem that is either local, NFS mounted, or a combination of the two. The best scenario depends on the function of the node and the situation.