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Chapter 38. Reporting Bugs

John H. Terpstra

Samba Team

Jelmer R. Vernooij

The Samba Team

Andrew Tridgell

Samba Team

27 June 1997

Table of Contents

Introduction
General Information
Debug Levels
Debugging Specific Operations
Internal Errors
Attaching to a Running Process
Patches

Introduction

Please report bugs using Samba's Bugzilla facilities and take the time to read this file before you submit a bug report. Also, check to see if it has changed between releases, as we may be changing the bug reporting mechanism at some point.

Please do as much as you can yourself to help track down the bug. Samba is maintained by a dedicated group of people who volunteer their time, skills and efforts. We receive far more mail than we can possibly answer, so you have a much higher chance of a response and a fix if you send us a “developer friendly” bug report that lets us fix it fast.

Do not assume that if you post the bug to the comp.protocols.smb newsgroup or the mailing list that we will read it. If you suspect that your problem is not a bug but a configuration problem, it is better to send it to the Samba mailing list, as there are thousands of other users on that list who may be able to help you.

You may also like to look though the recent mailing list archives, which are conveniently accessible on the Samba Web pages at http://samba.org/samba/.

General Information

Before submitting a bug report, check your config for silly errors. Look in your log files for obvious messages that tell you've mis-configured something. Run testparm to check your config file for correct syntax.

Have you looked through The Samba Checklist? This is extremely important.

If you include part of a log file with your bug report, then be sure to annotate it with exactly what you were doing on the client at the time and exactly what the results were.

Debug Levels

If the bug has anything to do with Samba behaving incorrectly as a server (like refusing to open a file), then the log files will probably be quite useful. Depending on the problem, a log level of between 3 and 10 showing the problem may be appropriate. A higher level gives more detail, but may use too much disk space.

To set the debug level, use the log level in your smb.conf. You may also find it useful to set the log level higher for just one machine and keep separate logs for each machine. To do this, add the following lines to your main smb.conf file:

log level = 10
log file = /usr/local/samba/lib/log.%m
include = /usr/local/samba/lib/smb.conf.%m

and create a file /usr/local/samba/lib/smb.conf.machine where machine is the name of the client you wish to debug. In that file put any smb.conf commands you want, for example log level may be useful. This also allows you to experiment with different security systems, protocol levels and so on, on just one machine.

The smb.conf entry log level is synonymous with the parameter debuglevel that has been used in older versions of Samba and is being retained for backward compatibility of smb.conf files.

As the log level value is increased, you will record a significantly greater level of debugging information. For most debugging operations, you may not need a setting higher than 3. Nearly all bugs can be tracked at a setting of 10, but be prepared for a large volume of log data.

Debugging Specific Operations

Samba-3.x permits debugging (logging) of specific functional components without unnecessarily cluttering the log files with detailed logs for all operations. An example configuration to achive this is shown in:

log level = 0 tdb:3 passdb:5 auth:4 vfs:2
max log size = 0
log file = /var/log/samba/%U.%m.log

This will cause the level of detail to be expanded to the debug class (log level) passed to each funtional area per the value shown above. The first value passed to the log level of 0 means turn off all unnecessary debugging except the debug classes set for the functional areas as specified. The table shown in Debugable Functions may be used to affect very precise analysis of each SMB operation Samba is conducting.

Table 38.1. Debuggable Functions

Function NameFunction Name
allpassdb
tdbsam
printdriversauth
lanmanwinbind
smbvfs
rpc_parseidmap
rpc_srvquota
rpc_cliacls

Internal Errors

If you get the message “INTERNAL ERROR” in your log files, it means that Samba got an unexpected signal while running. It is probably a segmentation fault and almost certainly means a bug in Samba (unless you have faulty hardware or system software).

If the message came from smbd, it will probably be accompanied by a message that details the last SMB message received by smbd. This information is often useful in tracking down the problem so please include it in your bug report.

You should also detail how to reproduce the problem, if possible. Please make this reasonably detailed.

You may also find that a core file appeared in a corefiles subdirectory of the directory where you keep your Samba log files. This file is the most useful tool for tracking down the bug. To use it, you do this:

$ gdb smbd core

adding appropriate paths to smbd and core so gdb can find them. If you do not have gdb, try dbx. Then within the debugger, use the command where to give a stack trace of where the problem occurred. Include this in your report.

If you know any assembly language, do a disass of the routine where the problem occurred (if its in a library routine, then disassemble the routine that called it) and try to work out exactly where the problem is by looking at the surrounding code. Even if you do not know assembly, including this information in the bug report can be useful.

Attaching to a Running Process

Unfortunately, some UNIXes (in particular some recent Linux kernels) refuse to dump a core file if the task has changed uid (which smbd does often). To debug with this sort of system, you could try to attach to the running process using gdb smbd PID where you get PID from smbstatus. Then use c to continue and try to cause the core dump using the client. The debugger should catch the fault and tell you where it occurred.

Sometimes it is necessary to build a Samba binary files that have debugging symbols so as to make it possible to capture enough information from a crashed operation to permit the Samba Team to fix the problem.

Compile with -g to ensure you have symbols in place. Add the following line to the smb.conf file global section:

panic action = "/bin/sleep 90000"

to catch any panics. If smbd seems to be frozen look for any sleep processes. If it is not, and appears to be spinning, find the process id of the spinning process and type:

gdb /usr/local/samba/sbin/smbd

then “attach 'pid'” (of the spinning process), then type “bt” to get a backtrace to see where the smbd is in the call path.

Patches

The best sort of bug report is one that includes a fix! If you send us patches, please use diff -u format if your version of diff supports it, otherwise use diff -c4. Make sure you do the diff against a clean version of the source and let me know exactly what version you used.