SSH Reference Manual

allow defining default values for these USER attributes on a global level. If multiple CPUs are configured, then these
will be used in a round-robin fashion.
Another way of load balancing of incoming SSH connections is to configure multiple IP processes for one SSH2 process
(see parameter SUBNET) and let users connect to different IP addresses of the NonStop system. In this way the TCP/IP
traffic load is distributed over the CPUs if the configured TCP/IP processes run in different CPUs.
Fault Tolerance
SSH2 can be configured to ensure constant availability of NonStop-based SSH applications across the network. Running
on the Guardian platform, SSH2 takes advantage of the fundamental availability characteristics of NonStop™.
SSH2 services can be configured as generic processes, enabling automatic recovery from failures, such as CPU outages.
SSH2 can also be started as a NonStop process pair. Both mechanisms will not prevent sessions to fail after the primary
CPU of the SSH2 process goes down. However, SSH2 will restart operation in a backup CPU, ensuring that clients can
reconnect immediately.
Configuring SSH2 as a NonStop Process Pair
SSH2 can easily be started as a NonStop process pair by specifying the BACKUPCPU parameter as follows:
RUN SSH2/ NAME $SSH00, CPU 0, .../ ALL; BACKUPCPU ANY; ...
In case of a failure of the primary CPU, the backup process of SSH2 will take over and restart the operation.
Configuring SSH2 as a Generic Process
The following sample SCF commands can be used to configure a SSH2 server as a generic process:
ALLOW ALL ERRORS
ASSUME PROCESS $ZZKRN
ABORT #SSH2
DELETE #SSH2
ADD #SSH2, AUTORESTART 10, &
HOMETERM $ZHOME, &
PRIORITY 158, &
PROGRAM $SYSTEM.COMFSSH2.SSH2, &
DEFAULTVOL $SYSTEM.COMFSSH2, &
NAME $SSH2, &
STARTUPMSG "SERVER; PORT 22; SUBNET $ZTC01; LOGCONSOLE *; &
LOGFILE SSHLOG ", &
STARTMODE MANUAL, &
USERID SUPER.SUPER , &
CPU FIRST
START #SSH2
INFO #SSH2
STATUS #SSH2
Before running SSH2 as a generic process, we recommend that you have a working RUN SSH2 command at the TACL
level. This command should be easy to convert to the respective SCF ADD command. For example, the SSH2 startup
line parameters are specified with the STARTUPMESSAGE parameter.
If running SSH2 as a generic process, we recommend that users send the SSH2 log output to a log file instead of writing
it to the home terminal, which is the default approach. In the example above, console logging is turned off, while log
messages are written to the SSHLOG file on the default volume.
If you want to configure multiple SSH2 servers listening on the same port with parallel library TCP/IP or TCP/IPV6
round-robin filtering, you may specify the filter key with the PTCPIPFILTERKEY
configuration parameter or add define
=PTCPIP^FILTER^KEY for the generic process (defines can be added to generic processes since G06.28/H06.06).
HP NonStop SSH Reference Manual Configuring and Running SSH2 • 135