dtrace discuss - Jul 2006 - debugging approach using dtrace and opensolaris(Source)

Hi,

  recently encountered a situation where a NFS mount  failed with error
message "permission denied" (client & serverSolaris10 ). After
sometime figured that it was a misspelled server path name after enabling
verbose mode for mountd. I was thinking at that point that I should be able to
find the actual problem using the opensolaris source code and dtrace.
 Any suggestions on how one would get closer to the acutal problem using dtrace
and source code? Is there a generic approach that can be taken in these
situations?

  Should one be looking for failed functions/system calls and how to relate back
to an area of source code?  Is this a valid use of these tools?

Thanks
 
 
This message posted from opensolaris.org

On Tue, 18 Jul 2006, Ashok Nair wrote:
> Hi,
>
>  recently encountered a situation where a NFS mount  failed with error
> message "permission denied" (client & serverSolaris10 ).
After sometime
figured that it was a misspelled server path name after enabling verbose
mode for mountd. I was thinking at that point that I should be able to find
the actual problem using the opensolaris source code and
dtrace.
> Any suggestions on how one would get closer to the acutal problem using
dtrace and source code? Is there a generic approach that can be taken in
these situations?
>
> Should one be looking for failed functions/system calls and how to relate
back to an area of source code?  Is this a valid use of these tools?

Hi Ashok,

I typically prefer to use truss to debug problems like the one you 
described above. Truss has several nifty options for decoding structures, 
allows you to limit your results to specific system and library calls,
and most importantly allows you to follow on fork ( DTrace doesn''t have
direct support for this yet). As far as debugging with DTrace, you might 
be interested in the following PDF:

http://opensolaris.org/os/community/documentation/files/studentguide.pdf

The studentguide shows how DTrace can be used to debug problems in the 
Solaris kernel, and contains some super useful information.

Thanks,
- Ryan
--
UNIX Administrator
http://prefetch.net