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Introduction (pmax-specific), Diskless NetBSD HOW-TO

If you don't find what you need here, then look in the old Netbooting NetBSD/pmax page

Client hardware requirements

All DECstation machines should be netbootable, however, there are some problems with netbooting some DECstations. This can depend on both the model and specific PROM version you have. Decstation PROMs support booting via either the DecNET MOP protocol, or via bootp and tftp.

The biggest hurdle with diskless booting is that the PROMs of each model of DECstation come in a variety of different versions, with bugs that break diskless booting in various ways. Some versions of PROMs only boot reliably with MOP, others only boot reliably with tftp. Experimentally, smaller kernels seem to boot where bigger kernels fail. (The generic installation kernel counts as "bigger" in this context).

The long-term solution is probably to write a small, secondary bootloader, boot that via the PROMS, and use it to download a real kernel. No one has yet written such a bootloader.

Here is a list of known PROM versions and whether people have found them to be netbootable or not.

More info on PROMs is available in the boot(8) man page and in the DS5000 PROM manual (section C).

Setting up the client hardware

How the bootrom starts loading from a diskless server

Booting and running NetBSD/pmax over a network requires a BOOTP server, a TFTP server and an NFS server. (These are usually all run on the same machine.) There are two basic stages to the boot:

  1. The PROM software sends a BOOTP request to get its own address, the address of the TFTP server and the kernel to download. After loading the kernel into memory, it executes it.

  2. The kernel probes and configures the devices, and then sends out another BOOTP request so it can find out its address, the NFS server, and path. It then mounts its root via NFS and continues.

A few things worth noting

Begin setting up your kernel

Get pmax/binary/kernel/nfsnetbsd.gz from the NetBSD distribution and gunzip it. This is what will be sent by TFTP. It is a small ecoff kernel (small to workaround PROM bugs). Copy this file to /tftpboot.

  1. bootpd
  2. tftpd
  3. nfs
  4. client filesystem
  5. finishing up

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