+-----------------------------------------------------------------------
| Customizing ${PKGSTEM} execution on OpenBSD
+-----------------------------------------------------------------------

Caution regarding built-in Webserver
====================================

The Hercules program allows for configuration to enable a webserver
with included CGI binaries to display System/370 registers and status.

It connects to all IPv4 interfaces and is generally accessible
without a password.

You should carefully consider your PF configuration to limit
access to this webserver.

Additionally, most System/370 operating systems support 3270-style
terminals.  (The x3270 package is useful here.)  The virtual
machines will open port 3270 and connect to all IPv4 addresses.

Sample pf.conf entries (assuming the webserver at port 8081):

    # Do not permit remote connections to Hercules VMs
    block return in on ! lo0 proto tcp to port 3270
    block return in on ! lo0 proto tcp to port 8081

Sources for System/370 operating systems
========================================

For downloadable public-domain System/370 operating systems see

    https://www.ibiblio.org/jmaynard/

and

    https://try-mts.com/

and 

    https://www.hercules-390.eu/hercfaq.html

At least MTS and VM/370 are known to work.

Instructions for Initial Use
============================

The downloadable files (usually zip files) contain a Hercules
configuration file (such as vmsys.cnf) as well as disk images
of simulated disk drives.  The cnf file will configure
the emulated devices such as disks, terminals, consoles and
card readers and punches.

After configuration completes, the next command to Hercules is

Command==> ipl 260

(or whichever disk drive is documented).  This performs a boot,
called initial program load IPL of the operating system.
