IBM Support

Capturing Debug Boot Output With An HMC

Question & Answer


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


Setting up the software on a PC

Capture the console output by logging in to the HMC via an SSH client such as PuTTY, with logging enabled. This action saves the output in a file on the user's PC.

  • 1. Configure an SSH client (for example 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. Display the menu of managed servers by running the command "vtmenu". If there is only 1 managed server, this action displays a list of LPARs available to connect to.

    4. At the vtmenu, select the server to which you require a console session.

    5. Select the LPAR from which you need boot debug.

    6. Wait for "Open completed" message.  If the LPAR is running, it displays a console login prompt.

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, activate the menu and select "Operations -> shutdown".

    2. Wait until the LPAR is in a "Not Activated" state, and the Reference Code shows all zeros.

    3. Mouse click the arrows to the right of the LPAR name again to display the menu. Click "Operations -> Activate -> Profile"

    4. From the Activate Logical Partition window, click the "Advanced" button.

    5. From the Activate Logical Partition - Advanced button window, select "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" 

    For the newest power9 firmware with the restricted open firmware prompt, use the new command “BOOT_FROM_SEQ -s verbose”

  • 2. For optical drive boot debug, enter:
    0> boot cdrom:\ppc\chrp\bootfile.exe -s verbose
  • For the newest power9 firmware with the restricted open firmware prompt, you can no longer specify a boot device by using the open firmware path syntax. Use SMS menus to set the boot list, then at the open firmware prompt use “BOOT_FROM_SEQ -s verbose"

  • The LPAR continues to boot and debug information is displayed on the console. While the LPAR is booted in this debug state, all commands that are run display 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 is 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, type the characters tilde and dot.
    • ~.

    The console prompts you to terminate the connection. Type "y" to be disconnected from the virtual console.

    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.

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Document Information

Modified date:
28 March 2024