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

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

• Determining your ethernet hardware address

  You will need to determine the ethernet hardware address of your workstation, and which slot has your ethernet card (or motherboard ethernet). The ethernet hardware address is sometimes also known as the "link level address" or MAC. It is a twelve digit hexadecimal number (i.e. it uses 0-9 and A-F for each digit). For example, 08:00:09:09:45:84 is the ethernet address of my HP workstation.

  On a DS5000 (and possibly others), the PROM cnfg command will list the MAC addresses and slot numbers of all ethernet cards. Here is an example from mcmahill@mtl.mit.edu's DS5000/200 with an ethernet card in addition to the built-in ethernet:

  >>cnfg
   7: KN02-AA  DEC      V5.3c    TCF0  ( 96 MB)
   6: PMAD-AA  DEC      V5.3a    TCF0  (enet: 08-00-2b-1b-c1-24)
   5: PMAZ-AA  DEC      V5.3b    TCF0  (SCSI = 7)
   1: PMAD-AA  DEC      V5.3a    TCF0  (enet: 08-00-2b-1a-80-19)
  

  Slot 6 has his motherboard ethernet, and slot one is his ethernet card. Option slots 0, 1, and 2 are the three places you can plug in boards. #0 is the left hand one looking at the back of the computer, they are labeled "0" "1" "2".

  If you've got an ethernet card, you replace the motherboard slot number with the slot of your card (i.e. replace 3 or 6 with 0, 1, or 2) when running the boot command.

  The only Ethernet device the PROM on most PMAX systems knows how to boot from is the PMAD-A (which includes onboard Ethernet interfaces and add-on cards). The PROM also knows how to boot from a FDDI card with tftp, but there is no known reports of this actually working with NetBSD/pmax.

• Temporarily overriding the default boot device order

  To get to the boot prompt, hit control-C during a normal boot or autoboot. Otherwise, halting an OS and (depending on the haltaction environment variable) simply powering on or resetting the machine will present the boot prompt.

  At the boot promt, run the following command to boot from your motherboard ethernet:

  Model	Boot command (using motherboard ethernet)
  5000/xx, 5000/1xx, 5000/240, 5000/260	boot 3/tftp
  5000/200	boot 6/tftp
  2100, 3100	boot -f tftp()

• Permanently overriding the default boot device order

  For a DecStation 2000/3000, type at the boot prompt:

  setenv bootpath [args]

  Where [args] is the boot path to your kernel. For a netboot kernel, this would be located at tftp(). For a disk-based kernel, this would be located at rz(0,1,0)netbsd.

  For a DECStation 5000, type at the boot prompt:

  setenv boot "[args]"

  Where [args] is the command you use to boot your machine. For a netboot kernel, this would be 6/tftp (where 6 is the slot of the ethernet device you want to use). For a disk-based kernel, this would be 5/rz0/netbsd -a (where 0 is the SCSI ID of the boot drive, 5 is the SCSI slot, and the kernel uses the -a flag).

  You can also set the machine to automatically run the boot command with your settings by typing the following at the boot prompt:

  setenv haltaction b

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

• You may consider trying to use mop (coming soon) instead of bootp and tftpd to load your kernel. Apparently, the PROM command is 3/mop instead of 3/tftp for DECstation 5000.

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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