Topics: AIX, System Admin

Howto setup AIX 'boot debugger'

The AIX kernel has an "enter_dbg" variable in it that can be set at the beginning of the boot processing which will cause all boot process output to be sent to the system console. In some cases, this data can be useful in debugging boot issues. The procedure for setting the boot debugger is as follows:

First: Preparing the system.

Set up KDB to present an initial debugger screen

# bosboot -ad /dev/ipldevice -I
Reboot the server:
# shutdown -Fr
Setting up for Kernel boot trace:

When the debugger screen appears, set enter_dbg to the value we want to use: 
************* Welcome to KDB *************
    Call gimmeabreak...
    Static breakpoint:
    .gimmeabreak+000000     tweq     r8,r8    r8=0000000A
    .gimmeabreak+000004      blr
<.kdb_init+0002C0> r3=0
    KDB(0)> mw enter_dbg
    enter_dbg+000000:  00000000  = 42
    xmdbg+000000:  00000000  = .
    KDB(0)> g
Now, detailed boot output will be displayed on the console.

If your system completes booting, you will want to turn enter_dbg off: 
************* Welcome to KDB *************
    Call gimmeabreak...
    Static breakpoint:
    .gimmeabreak+000000     tweq     r8,r8    r8=0000000A
    .gimmeabreak+000004      blr
<.kdb_init+0002C0> r3=0
    KDB(0)> mw enter_dbg
    enter_dbg+000000:  00000042  = 0
    xmdbg+000000:  00000000  = .
    KDB(0)> g
When finished using the boot debugger, disable it by running:
# bosdebug -o
# bosboot -ad /dev/ipldevice




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