About EtherBoot
Etherboot is a software package for creating ROM
images that can download code over an Ethernet network to be
executed on an x86 computer. Many network adapters have a socket
where a ROM chip can be installed. Etherboot is code that can be
put in such a ROM. Etherboot is normally used for for booting PCs
diskless. This is useful in various situations, for example:
- An X-terminal.
- Clusters of compute servers.
- Routers.
- Various kinds of remote servers, e.g. a tape drive server that
can be accessed with the RMT protocol.
- Machines doing tasks in environments unfriendly to disks.
- A user platform where remote partitions are mounted over the
network and you are willing to accept the lower speed compared to
disk.
- Maintaining software for a cluster of equally configured
workstations centrally.
Etherboot can boot computers faster than from a disk
because there are no delays in spinning up disks, etc. A moment's
calculation will show that even with a 10Mbit Ethernet, sending a
500kB kernel will take only a couple of seconds typically. With
100Mbit Ethernet it gets even better.
Compared to booting from solid-state devices, e.g.
Flash disks, Etherboot has the advantage of centralising software
adminstration, the tradeoff being the dependence on a server. This
can be partly alleviated by providing redundant servers.
Etherboot can work with RAM disks, NFS filesystems,
or even local disks, if desired. It's a component technology and
can be combined with other technologies to do things the way you
want.
Etherboot is usually used to load Linux, FreeBSD or
DOS. However the protocol and boot file formats are general, so
there is no reason why it could not be used to load arbitrary
images to a PC, including other OSes.
Etherboot is Open Source under the GNU General Public
License Version 2 (GPL2).
The components needed by Etherboot are
- A bootstrap loader, usually in an EPROM on a network card, or
installed in the flash BIOS, but could be put anywhere in the
address space the BIOS probes in. For testing this could be put on
a floppy disk or a hard disk partition. Some configurations may
even be always run from a floppy disk (e.g. temporary testing
setups or pedagogic uses).
- A DHCP or bootp server, for returning an IP address and other
information when sent a MAC (Ethernet card) address.
- A tftp server, for sending the kernel images and other files
required in the boot process. Alternatively, Etherboot can boot
from an NFS mount.
- A Linux or FreeBSD kernel.
- Optionally, a NFS server, for providing the disk partitions
that will be mounted if Linux or FreeBSD is being booted.
- Optionally, a RAM disk contained in the loaded image. This can
be the initial RAM disk if desired.
- Software tools for building the download image, and tools for
debugging.
