Booting VAXen From The Network

Sometimes it is very useful to be able to boot a VAX from the network. The two most common scenarios are

  1. Your machine is diskless. As time goes on this is going to be more and more common as SCSI disks die out.
  2. You have a disk in the machine and you have the VMS media, but you don’t have devices to load the media from.

In these scenarios booting from a running instance of VMS is the easiest way to get your machine running, and the best bit is that you don’t even need it to be running on physical hardware. I use the wonderful SIMH emulator to run VMS, and I use it as the boot node for getting other VAXen running. You need your boot node to be in a cluster and then add the real VAX as a satellite to the cluster.

I am assuming that you have VMS running on SIMH. If you need to understand how to install VMS then Phil Wherry’s page is a great start. Some notes to consider when following these instructions follow:

  • Make sure you select to install DECnet Phase IV
  • You may want to include DECwindows support too if you want to run it on a real diskless VAX.
  • When prompted for the SCSSYSTEMID you can use the suggested value of 1025, which equates to a DECnet node address of 1.1. However, if you are likely to want to get on HECnet, or run this machine as part of an existing DECnet network then you may want to use another value. To set your node address as N.M, the SCSSYSTEMID is calculated as N * 1024 + M.

Once VMS is up and running, login as SYSTEM, register a DVNETEND and a VAXCLUSTER license. The first step is to set up DECnet, but this is only so that you can communicate between the boot node and the satellite using DECnet. To configure DECnet run @NETCONFIG. For the node address use the address that corresponds to the SCSSYSTEMID you used above, so if you used 1025, then enter a node address of “1.1”. You do not need the node to operate as a router (and you need to register a DVNETRTG license if you do). I then choose all the defaults when asked about accounts. Finally edit the SYSTARTUP_VMS.COM file so that DECnet is started automatically (uncomment the line START/NETWORK DECNET).

Now you are ready to setup the boot node as a cluster. To do this run @CLUSTER_CONFIG_LAN. Choose option 1 to ADD <node> to existing cluster, or form a new cluster, then choose to use the LAN for cluster communications. The cluster’s group number just needs to be a unique number with respect to any other clusters you may have, unless you want it to be part of an existing cluster. Select Y when asked if it will be a boot server (obviously, that is the whole point here). For the ALLOCLASS I used the second number in the node’s DECnet address (for address M.N, I used N for the ALLOCLASS).

After the machine has rebooted it is time to add the VAX as a satellite. Login as SYSTEM. I found I had to run the following commands, although I am sure I have not had to that before


Then run @CLUSTER_CONFIG_LAN, select 1 to ADD a VAX node the cluster, then select that the node will be a satellite. Give the node a name and an SCSSYSTEMID that translates to a DECnet address. The hardware address for the new node’s LAN adapter is its MAC address. Once the satellite has been configured, just start up the physical machine and tell it to boot from the network adapter.

There is a full transcript here.

If you have a local disk on the satellite then you can mount the disk and restore the basic VMS saveset to the disk. I then copy the remaining savesets onto the same disk, so that when I boot off the physical disk I say the remaining media is on the same disk. That is how I install VMS onto a physical disk from the network.


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