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Booting AIX in Debug Mode

December 20, 2016

I recently had an AIX LPAR that wasn't booting. In an effort to gather information, IBM Support had me boot it a few different ways. This document details what we needed to do. I'm copying it here because I want to make sure you're aware of this option.

How to enable verbose (debug) output during boot and capture it for later analysis by IBM.
Note this technique is for customers using an HMC to manage their systems.

We will capture the console output by logging in to the HMC via an SSH client such as PuTTY, with logging enabled. This will save the output in a file on the user's PC.

1. Configure an SSH client (eg PuTTY) to log session output to a local file on the PC.
2. Open a connection to the HMC and login as user 'hscroot'.
3. Bring up a menu of managed servers by running the command "vtmenu". If there is only 1 managed server this will bring up a list of LPARs available to connect to.
4. At the vtmenu, select the server to which you desire a console session.
5. Select the LPAR from which you need boot debug.
6. Wait for "Open Completed" message (if LPAR were Running you would get a Console: login)

Booting the LPAR to the Open Firmware (OK) prompt
1. Make sure the LPAR is not activated. If it is hung, go to the HMC GUI, and under Systems Management -> Servers -> server name, check the box next to the LPAR. Then from the arrow on the right side of the LPAR name, popup the menu and select "Operations -> Shut Down".
2. Wait until the LPAR is in a "Not Activated" state, and the Reference Code shows all zeros.
3. Mouse click on the arrows to the right of the LPAR name again, to get the popup menu. Click "Operations -> Activate -> Profile"
4. From the Activate Logical Partition popup window, click the "Advanced" button.
5. From the Activate Logical Partition - Advanced popup window, click "Open Firmware OK Prompt" from the Boot Mode drop down list.

Enabling the debug boot image
1. Back in the SSH console session window, wait for the Open Firmware prompt "0>"
At the 0> prompt, enter "boot -s verbose"

2. For cdrom boot debug enter:
0> boot cdrom:\ppc\chrp\bootfile.exe -s verbose

At this point, the LPAR will continue to boot and debug information will be sent to the console. While the LPAR is booted in this debug state, all commands that are run will output debug information, such as exec() system calls.

Capturing the debug information
The console session is being run via the SSH connection to the HMC and the output will be captured in the log file configured in the first step. Once the system boot fails or hangs, stop the LPAR and send the boot debug log file to IBM Support for review.

Finishing up
To disconnect from the virtual console you have selected, type the characters tilde and dot.

The console will ask if you wish to terminate the connection. Type "y" to be disconnected from the virtual console.

At this point you can type <ENTER> to stay in the vtmenu session and choose another console, or type "q" to quit back to the HMC shell prompt.

If you are quitting, then type "exit" to close the HMC ssh session and quit the putty tool.

Once we had collected the data, IBM was able to help determine the problem.

As a reminder, you can also get debug information from your VIO server as well, using this technique:

    Login to VIOS as padmin
    $ oem_setup_env
    # script -a /home/padmin/<PMR#.Branch#>clidebug33.out
    # su - padmin
    $ ioslevel
    $ uname -LMm
    $ export CLI_DEBUG=33
    Run offending command to reproduce error
    $ export CLI_DEBUG="" (to disable debugging mode)
    $ exit (padmin)
    # exit (script)

Posted December 20, 2016 | Permalink

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