Knowledgebase

Issue:

SUN Sparc OK prompt using the break signal.

Solution:

The definition of a headless system is one that does not have an attached keyboard or does not have a Sun console. It will by default send the boot information out serial port A if the keyboard or console are not attached. Serial port B can also be used.

Attach using NULL modem cable to:

-An ascii terminal- For example, Wyse terminal
-Another Sun workstation that has a Sun console
-A Network terminal concentrator/server

Technical Support does not recommend booting off a serial port with a modem attached or not having any type of console.

A console allows the ability to send a break signal dropping the system to the OK prompt for diagnostics. The console device is

/dev/console.

--------------------------------------

A. Open Boot Prom:

To check the current settings use the printenc command:

OK> printenv

...
ttyb-rts-dtr-off false false
ttyb-ignore-cd true true
ttya-rts-dtr-off false false
ttya-ignore-cd false true
ttyb-mode 9600,8,n,1,- 9600,8,n,1,-
ttya-mode 9600,8,n,1,- 9600,8,n,1,-
...

Use the setenv command to change parameters

OK> setenv output-device ttya
OK> setenv input-device ttya

Note: the above is not necesary on tty A if the keyboard is disconnected. It is necessary to change these setting for serial port B regardless.

Additional settings:

ttya-rts-dtr-off= false or true
ttya-ignore-cd= true or false

Syntax for changing Open Boot Prom value:

OK> setenv ttya-rts-dtr-off false
OK> setenv ttya-ignore-cd true

Use printenv to verify the following settings:

ttya-mode=9600,8,n,1,-

To change:

OK> setenv ttya-mode 9600,8,n,1,-

Run the "reset" command to make the above settings take effect

OK> reset

B. The terminal type, /etc/inittab and port monitors

Do not start port monitor services for the serial port. Verify with pmadm -l. Make sure there are no listings for the tty port that is acting as the console. (Solaris 2.5 ttya and ttyb have port monitor services enabled for modem logins by default- These services need to be removed)

To remove type:

pmadm -p zsmon -r -s

SVCTAG will be ttya or ttyb.

/etc/inittab takes care of setting the console port characteristics with the following line:

co:234:respawn:/usr/lib/saf/ttymon -g -h -p "`uname -n` console login: " -T sun -d /dev/console -l console -m ldterm,ttcompat

By default the console terminal type is "sun" specified with the -T option above. This means that for ascii terminals vi will not work. In order for programs like vi to work the TERM variable needs to be changed to match the "personality" of the terminal. This can be done by modifing -T in /etc/initab to 'vt100' (for example) or changing the TERM variable in .login, .profile, or .cshrc or at the command line, for example:

setenv TERM vt100

C. Sending a Break Signal

Unpluging the serial cable is the equivalent to sending a break and will bring the Sun box down to the OK prompt. If the cable was not attached during bootup plugging it in may send a break. When some Network Terminal Servers are rebooted this will also send a break and bring the Sun boxes down to the OK prompt [CS9000 or Iolan SDS reboot will not cause this to occur].

Note: you must have full hardware signalling on the cable you use from the console/terminal server to the SUN serial port.

See links below for additional information.

Related Articles:
1.) How to send a 'break' on an Iolan+ reverse telnet connection.
2.) How to initiate a hardware break within a telnet session

1.) 

Perle cabling diagrams