Going Multiuser

Yup, Helios is a Multitasking-Multiuser OS… but not quite as you might got used to it using UNIX(ish) OSes in recent times. There are some caveats:

Theory

As Helios is running on Transputers (mostly) and Transputers do not feature an MMU, there’s no ‘protected’ multitasking, i.e. a badly written application can kill (at least) the Transputer it is running on, if not the whole network. This might bring back memories of Apples System 7.x “Multi Finder” or Windoze 95 and other cooperative multitaskting solutions.
The only half-way robust way to really protect Helios processes is to ‘lock them away’ into a dedicated Transputer.

Running Multiuser (ie. providing remote login etc.) means you need at least 2 Transputers. To protect certain essential services like ‘netserver’ and ‘sessionmanager’ those have to run on the “root Transputer” (/00) which is not accessible to any user – including root. Logging in from the console on your PC will automatically put you onto the next Transputer in-line, eg. /01.
In consequence, if you like to have another user logging in over ‘telnet’ or serial console you’ll need another Transputer for that user (making it 3 in total).

Practice

So what do we need to configure to go Multiuser? First you should have your Transputer network configured and running as described 2 posts before this.
Then we check the nsrc file found in Helios’ /etc folder. Because I couldn’t say it better, I’ll copy from the Manual:
The nsrc file contains a list of options for the networking software, like the host.con
file which has a list of options for the I/O server. The nsrc file is read by the startns
program when networking software is started up, and passed in the environment to
the network server and/or Session Manager.”
(Just a refresher: network, networking and server means Transputer networks, no TCP/IP stuff and such.)

It should look somehow like this:

# root_processor = /Bozo/01
# single_user
# password_checking
# processor_protection
# no_taskforce_manager
share_root_processor
preload_netagent
waitfor_network
# 30 seconds is the default interval, -1 disables network monitoring
#monitor_interval = 10

I won’t go into every detail of each setting – there’s a Manual for that (p.58). Just make sure that ‘single_user’ is commented. For the curious amongst you: share_root_processor means the taskforce-manager, network-server and session-manager may run on the same CPU. If Helios runs in Multiuser mode like we are going to do, this is ignored anyway.

That’s it. If everything worked as described, Helios will boot all processors (but showing only /01 and /02) and logging in locally on your host machine will put you on Transputer /01. Users logging in via telnet will automatically put onto Transputer /02. This is a ps output entered in a telnet session:

% ps /00 /01 /02
Processor 00
ProcMan.0           Loader.1            netserv.4
Pipe.5              session.7           login.9
Processor 01
ProcMan.0           Loader.1            tcpip.3
inetd.4             Pipe.6              tfm.27
shell.28            telnetd.31          ttyserv.32
login.33
Processor 02
ProcMan.0           Loader.1            tfm.3
Pipe.4              shell.5             ps.7

The (inaccessible) Root-Transputer /00 is running the netserver and session-manager.
Processor /01 does the TCP/IP, inetd and telnetd handling, runs a shell (local login), cares for tty and runs a taskforce-manager (needed for parallel programs).
Finally processor /02 is the one the telnet-user actually lives and triggered the ps command from its shell.

So after all this configuring we have multiple Transputers running, TCP/IP is there and we can host multiple users (given we have enough Transputers to host them)… next and final step: X-Window!

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