Debugging mysqld crashes ======================== Author: Michal Marek Last modified: 2014-11-21 Contents -------- 1) Query log 2) Coredumps and Backtraces 3) Trace files In case your MySQL server crashes, here are some hints on what to include in a bugreport at https://bugzilla.novell.com/ . Please report there only bugs in the MySQL packages packaged by Novell/SUSE, bugs in binaries / source provided by MySQL AB should be reported at http://bugs.mysql.com/ . 1) Query log ------------ Note: Skip this chapter if you already have an exact query that crashes the server To find out which query possibly crashed the server, add the following line to your /etc/my.cnf into section [mysqld]: log=/var/lib/mysql/mysqld-query.log Mysqld then will, at some performance cost, log all queries into this file. After a server crash, you can examine the queries from the time it crashed and try to reproduce the crash with single queries (this might not allways work, eg. if the crash is caused by some race condition). Note that this log file may become extremly large, so if you decide to attach it whole to the bugzilla, don't forget to xz -k9 /var/lib/mysql/mysqld-query.log and attach the xzipped file instead. 2) Coredumps and Backtraces --------------------------- Another valuable information for the developers is the backtrace. The easies way to get one is to let mysqld produce a coredump. Add the following line to your /etc/my.cnf into section [mysqld]: core-file The core file will be written to the /var/lib/mysql/ directory. I suggest setting the kernel variable kernel.core_uses_pid to 1 sysctl -w kernel.core_uses_pid=1 so that the coredumps don't overwrite each other if you experience multiple crashes. After you got the core file, install the gdb and mysql-debuginfo packages and run gdb /usr/sbin/mysqld /var/lib/mysql/ (gdb) bt Replace the with the actual name of the coredump. 3) Trace files -------------- The trace file will contain various debug information and function calls/returns and will become _extremly_ huge after a while, so don't attach it to bugzilla unless requested. Add the following line to your /etc/my.cnf into section [mysqld]: stack-trace The trace file will be then written to /var/lib/mysql directory.