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Making a workstation "headless"

To use an IRIX system without a monitor and keyboard attached (i.e. "headless") the NVRAM must be set so that this configuration is recognized and not interpreted as an error. When the SGI machine is set to boot in this way, the only ways to connect to it are through a serial console or a valid network connection. Even without its own monitor, it is still possible to use the machine as a headless desktop.

The key variable is "console". To set this from the PROM monitor:

>> setenv console d

To set this from a root prompt:

# nvram console d

To boot normally again, change this value back to "g".

      • ATENTION***: If you set nvram console d, the monitor will show NOTHING until X loads. So, if you use normally your machine, take care when you set "console" to "d". To make everything normal, login via telnet and change again "console" to "g". Guess how I discovered it? :)

Be sure to disconnect all keyboards/mice if you connect via a serial terminal

External links

Obsolete : Booting an SGI Headless

An SGI server is headless by definition and is usually operated via remote network sessions and/or by a null modem (serial) cable.

Connecting to a headless machine via a null modem (serial) cable

General procedure

To use a terminal on a SGI machine dumb/diagnostic serial port #1, first disconnect the SGI keyboard from the machine.

Then connect a vt100 terminal, PC/Notebook terminal emulation, Hyper- terminal or similar to serial port #1 using a null modem cable.

Configure the serial connection for 9600 baud, 8 bits, no parity, 1 stop bit. Unless it is a newer machine of the final MIPS era of SGI Tezro, Origin3x0, and SGI Fuel. In which case use 38400 baud, 8bits, no parity, 1 stop bit.

With the terminal connected, reboot the machine and check for any power-on diagnostic messages.

To stop at the maintenance screen, hit ESC when the "Press ESC to enter ... " message comes up. Some terminals/emulators use a key combination to generate ESC (for instance, CTRL-ESC).


Make sure that your connection from the terminal to the SGI acts as a null-modem so that not both ends of the cable transmit or receive on the same wires but that the respective wires are crossed.

Null-modem cable

It is usually no problem to get a null-modem cable. It can be obtained from most PC stores for a few dollars. The problem is that the null- modem cable sometimes has not the appropriate plug to connect it to the SGI machine.

For instance, you can get a null-modem cable with two female DB9 connectors to connect your PC with a terminal emulation program to an SGI O2. However, this won't work with a SGI Indy.


To modify an existing null-modem cable or to build a null-modem cable yourself one needs to know the pinouts. See 'man 7 serial'.

Some pinout examples:

The DB-9 male serial port connectors on O2 (R5k, R10k), OCTANE, Onyx2, Origin2000 and Origin200 systems have the following IBM(R) PC/AT(tm)-like pin assignments:

\ 1 2 3 4 5 /
\ 6 7 8 9 /

Pin | Name | Description
1 | DCD | Data Carrier Detect
2 | RD | Receive Data
3 | TD | Transmit Data
4 | DTR | Data Terminal Ready
5 | GND | Signal Ground
6 | DSR | Data Set Ready (not used on Indy)
7 | RTS | Request To Send
8 | CTS | Clear To Send
9 | RI | Ring Indicator (not used on Indy)

The DB-9 female serial port connectors named "System Console" or "tty1" on Challenge (Eveready and Terminator) systems have the following pin assignments:

\ 5 4 3 2 1 /
\ 9 8 7 6 /

Pin | Name | Description              If you want to make a DIY cable for a DB9-male connector e.g. in a PC, use this wiring:
____|______|____________________      PC DB9F      SGI Side DB9M (required connectors)
1 | -  | unused                        1 | unused | /               
2 | TD | Transmit Data                 2 ---------- 2
3 | RD | Receive Data                  3 ---------- 3
4 | RTS | Request To Send              4 | unused | / 
5 | CTS | Clear To Send                5 ---------- 7
6 | GND | Signal Ground                6 ---------- 9
7 | GND | Signal Ground                7 ---------- 5
8 | DCD | Data Carrier Detect          8 ---------- 4
9 | DTR | Data Terminal Ready          9 | unused | /

The DIN-8 serial port connectors on the Indigo, Indy, Indigo2, Challenge S, Challenge M, Power Challenge M, and the MENET 4-Enet, 6-serial board (XT-FE-4TX-6A) have the following pin assignments.

/ 8 7 6 \
( 5 4 3 )
\ 2 1 /

_4D Compatible Pin Assignments (RS-232)
Pin | Name | Description
1 | DTR | Data Terminal Ready
2 | CTS | Clear To Send
3 | TD | Transmit Data
4 | SG | Signal Ground
5 | RD | Receive Data
6 | RTS | Request To Send
7 | DCD | Data Carrier Detect
8 | SG | Signal Ground

Building a null-modem cable yourself

Normally it is sufficient to buy a null-modem cable for your terminal or PC running a terminal program and to prepare the other end to connect to the SGI machine serial port if it doesn't fit already.

The SGI side of the cable can be prepared

- by applying an appropriate adapter between the null-modem cable and the SGI machine

- by cutting the existing connector off the null-modem cable and applying the right connector using the appropriate pinout scheme.

To build the cable from scratch, you need the cable and the appropriate connectors (see 'man 7 serial'). At minimum you need to build a three- wire cable to go from the SGI machine serial port #1 (/dev/ttyd1) to COM1 of your PC.

The minimum connections required are Receive (RX), Transmit (TX), and Signal Ground (SG). RX on one end goes to TX on the other end, TX on one end goes to RX on the other end, and SG goes to SG.

Composing a null-modem cable from ready-made parts

A null-modem cable with the appropriate connectors may be composed by means of available cables and adaptors.

For instance, to connect a SGI Indy to a PC one would need:

1. a MiniDIN8/DB25, M/M, 8C, 6FT adaptor to connect to the Indy.

2. a DB25/DB25, M/F, 8C, 6FT null-modem cable to connect with its female (F) DB25 connector to the male (M) DB25 connector of item 1.

3. a DB9/DB25, F/F, 8C, 6FT cable to connect with its female (F) DB25 connector to the male (M) DB25 connector of item 2.

The female (F) DB9 connector is then connected to your PC.

Where to get the required parts?

Greg Douglas of Reputable Systems (gdouglas (at) reputable.com) once said:

In the US, CompUSA or similar type computer stores carry Mac H/S modem cables, which work just fine for that purpose. You may also need a null modem adapter and/or DB-9 gender bender.

I sell these as complete kits (with Mini-DIN 8 to DB25, DB 25 gender bender, DB25 null modem adapter, and DB-25 - DB9 adapter for US$50. Unfortunately, I have a US$90 minimum order for international shipments (because of the amount of paperwork involved).

An even less expensive source would be National-Tech in the US


where you can buy the necessary adaptors and cables ready to plug into each other to build the required cable for about 20 US$.


The 'terminal' connected to a serial port of an SGI machine may be one of

  • a hardware terminal that emulates DEC VT100 characteristics
  • a PC running the terminal program under Windows 3.11
  • a PC running the HyperTerminal program under Windows
  • a PC running the TeraTerm program under Windows. The software is free and can be obtained from http://hp.vector.co.jp/authors/VA002416/teraterm.html
  • PuTTY program
  • cu - "connect unix" found on Free/Net/Open BSDs also found in the IRIX UUCP tardist.
  • a palm pilot using PalmTelnet that can be obtained from

http://netpage.em.com.br/mmand/ptelnet.htm> use 'pilot-xfer -s' with the pilot cradle on ttyf2 for backups, and move it to ttyf1 when you need to access the SGI dumb/ diagnostic serial port #1.

Connecting to the SGI machine

Connect the SGI machine to your terminal or PC running a terminal program. Configure the terminal or terminal program with

  • 9600 baud (38400 baud for later machines like Origin 300 and Tezro)
  • no parity
  • 8 bits
  • 1 stop bit
  • flow control off or on (one or the other may work)

Power-on the SGI machine. If you can see the "Press ESC to enter... " message on your terminal, then the protocol is correct. Some terminal emulators handle ESC in an odd way and require to press a key combina- tion to send an ESC character. CTRL-ESC is an example.

Testing the null-modem cable connection with a running SGI machine

There is no need for special drivers. As super-user try to write/read to/from the SGI serial port #2 for a test by 'echo file > /dev/ttyd2' and 'echo /dev/ttyd2' if this port is set-up appropriately in /etc/ inittab.


Originally almost entirely taken from nekonokos post: http://forums.nekochan.net/viewtopic.php?f=3&t=316&p=2094&#p2094

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