Capturing Boot Debug on Serial Console

Setting up the hardware

During installation with debug mode enabled, debug output is sent to the S1 serial port of the machine. This output can then be captured to a tty or other serial connection. The preferred method for capturing debug mode output is to have another system near to the client machine that can interface with it via an rs232 serial connection.

Hardware requirements for interfacing your AIX box with a client

• Two RS232 serial cables
• One gender changer
• One interposer (null modem)

[S1]--[X]----[R]----[I][G]----[R]----[X]--[Sx]

Setting up the interfacing system

1. Use the lslpp command to determine if bos.net.uucp is installed. Enter:

   lslpp -l bos.net.uucp
   

   Note: If not If you do not have this installed, you must install it from the AIX base installation media.
2. Set up the Sx port and create a tty on the port. To create the tty, enter:
   1. smitty tty
   2. Select Add a TTY
   3. Select tty rs232 Asynchronous Terminal
   4. Select Sx serial port
   5. Select the port number
   Note: Defaults
3. Create an uucp entry for created tty by editting the file /etc/uucp/Devices with your preferred text editor. Add the following:

   Direct tty0 - 9600 direct
   

4. Run the cu command piped to the tee command to capture the debug output. Enter:

   cu -ml tty0 | tee /tmp/boot.debuglog 
   

5. Disconnect from the client and stop logging by doing the following:
   1. ~.
   2. exit

Hardware requirements for interfacing a PC with your client

• Two RS232 serial cables
• One gender changer
• One interposer (null modem)

[S1]--[X]----[R]----[I][G]----[R]----[X]--[Sx]

Setting up HyperTerminal with client

1. Start Menu
2. Programs
3. Accessories
4. Communications
5. HyperTerminal
6. Name the session test then click Ok.
7. Under Connect using, select COM 1.
8. Enter the following Port Settings:

   Bits per second   9600

Data bits 8 Parity None Stop Bits 1 Flow control Hardware Click Ok when done. Note: If your client system has tty0 configured properly to the S1 port, you should see a login prompt in the hyperterminal screen.

9. Capturing the debug data from the HyperTerminal
   1. Click on Transfer drop-down menu in the HyperTerminal toolbar.
   2. Select Capture text.
   3. Enter a file name when prompted then click on Start

Capturing the debug information

1. Reboot your AIX box to begin data capture. Enter:

   sync
   sync
   reboot
   

2. Output should be displayed on your data capture system.
3. A debugger prompt(KDB>) should be displayed. Enter the following:

   KDB(0)> mw enter_dbg
   
   enter_dbg+000000:  00000000  = 42
   
   enter_dbg+000004:  00000000  = .
   
   KDB(0)> g
   
   

   Note: The debug is captured in the file /tmp/boot.debuglog on the AIX system or in the file name you specified in the hyperterminal session.

Stopping the KDB after debug is obtained

Debug output is obtained when system hangs. If machine boots normal, the KDB debugger can be stopped by doing the following,

1. Hit CTRL \
2. Enter the following sequence:
   1. mw enter_dbg
   2. 0
   3. .

bosboot -ad /dev/hdisk#