Booting a System With the Kernel Debugger (kmdb) Enabled

The following procedures are provided in this section:

• SPARC: How to Boot a System With the Kernel Debugger (kmdb) Enabled

• x86: How to Boot a System With the Kernel Debugger (kmdb) Enabled

If you need to troubleshoot system problems, running a system under the kernel debugger can be very helpful. The kernel debugger can help you investigate system hangs. For example, if you are running the kernel while the kernel debugger is active, and you experience a hang, you might be able to break into the debugger to examine the system state. Also, if the system panics, the panic can be examined before the system is rebooted. In this way, you can get an idea of which section of code might be causing the problem .

The following procedures describe the basic steps for troubleshooting system problems by booting with the kernel debugger enabled.

SPARC: How to Boot a System With the Kernel Debugger (kmdb) Enabled

This procedure shows how to load the kernel debugger (kmdb) on a SPARC based system.

1. Halt the system, causing it to display the ok prompt.

   To halt the system cleanly, use the halt command.

2. Type boot -k to request the loading of the kernel debugger. Press return.
3. Access the kernel debugger.

   The method used to enter the debugger depends on the type of console that is used to access the system:

   • If you are using a locally attached keyboard, press Stop-A or L1–A, depending on the type of keyboard.
   • If you are using a serial console, send a break by using the method that is appropriate for your type of serial console.

   A welcome message is displayed when you enter the kernel debugger for the first time.

   Rebooting with command: kadb
   Boot device: /iommu/sbus/espdma@4,800000/esp@4,8800000/sd@3,0
   .
   .
   .

Example 6-5 SPARC: Booting a System With the Kernel Debugger (kmdb) Enabled

The following example shows how to boot a SPARC based system with the kernel debugger (kmdb) enabled.

ok boot -k
Resetting...

Executing last command: boot kmdb -d
Boot device: /pci@1f,0/ide@d/disk@0,0:a File and args: kmdb -d
Loading kmdb...

x86: How to Boot a System With the Kernel Debugger (kmdb) Enabled

This procedure shows the basics for loading the kernel debugger. The savecore feature is enabled by default.

1. Boot the system.
2. When the GRUB menu is displayed, type e to access the GRUB edit menu.
3. Use the arrow keys to select the $multiboot line.
4. In the GRUB edit menu, type -k at the end of the $multiboot line.

   To direct the system to stop (break) in the debugger before the kernel executes, include -d option with the -k option.

5. To exit the GRUB edit menu and boot the entry you just edited, press Control-X. If you have a system with UEFI firmware, and you are not using a serial console, pressing F10 also boots the entry.

   Typing -k loads the debugger (kmdb), then directly boots the operating system.

6. Access the kernel debugger.

   The method used to access the debugger is dependent upon the type of console that you are using to access the system.

   • If you are using a locally attached keyboard, press F1–A.

   • If you are using a serial console, send a break by using the method that is appropriate for that type of serial console.

   To access the kernel debugger (kmdb) before the system fully boots, use the -kd option.

   Using the -kd option loads the debugger and then gives you an opportunity to interact with the debugger before booting the operating system.

   A welcome message is displayed when you access the kernel debugger for the first time.

See Also

For more detailed information about interacting with the system by using kmdb, see the kmdb(1) man page.