Numerous times now, I’ve seen people have troubles creating MySQL services on Windows manually (using ‘sc’), whether it be for mysqld itself, MySQL Proxy, or the MySQL Enterprise Monitor and/or Agent.

The proper syntax for ‘sc’ can get tricky when you have spaces in pathnames, which is very common in Windows, and the need for –defaults-file (which means two paths each potentially containing spaces).

So, if you have spaces in both your binpath and your path to –defaults-file, then the following syntax will work for you (all on a single line):

sc create MySQLEnterpriseMonitorAgent 
binpath= ""C:Program FilesMySQLEnterpriseAgentbinmysql-monitor-agent.exe" 
--defaults-file="C:Program FilesMySQLEnterpriseAgentetcmysql-monitor-agent.ini"" 
DisplayName= "MySQL Enterprise Monitor Agent" start= "auto"

Note that you could easily use the exact same syntax to install a Windows service for the MySQL server itself …

While some may think I’m daft, I have a legitimate reason for wanting to crash mysqld. However first we need to find a way to crash it.

Great thanks to Alan K, Mark L, Harrison and Hartmut on #mysql-dev for several suggestions and a config option I was unaware of. My investigation even lead to a documentation bug logged as #51739.

My first thought was to find a known bug and if necessary install the correct version to test that. A good one was suggested, Bug #48508 which fails on several versions that I will use to demonstrate with, however the simplest way is to issue kill -11

By default, no core file will be produced which is what I’m seeking but with the right options this is possible. First, the user running mysqld probably has a core file limit size of 0.

$ ulimit …

I was actually exploring inotify-tools for something else, but they can also be handy for seeing what goes on below a mysqld process. inotify hooks into the filesystem handlers, and sees which files are accessed. You can then set triggers, or just display a tally over a certain period.

It has been a standard Linux kernel module since 2.6.13 (2005, wow that’s a long time ago already) and can be used through calls or the inotify-tools (commandline). So with the instrumentation already in the kernel, apt-get install inotify-tools is all you need to get started.

# inotifywatch -v -t 20 -r /var/lib/mysql/* /var/lib/mysql/zabbix/*
Establishing watches...
Setting up watch(es) on /var/lib/mysql/mysql/user.frm
OK, /var/lib/mysql/mysql/user.frm is now being watched.
[...]
Total of 212 watches.
Finished establishing watches, now collecting …

Warning... what follows is a murky mess.
It's filed as MySQL bug#43398 (verified!) but it's triggered by cPanel doing evil.

Scenario....Start a mysql server, as normal
Then run mysql_install_db (as root, like you would when you first install MySQL)
See a new binlog file get created, with ownership/group root!Of course you generally wouldn't run mysql_install_db while a server is running, but there's nothing to prevent you (or something else) from doing so!
--bootstrap just shouldn't initialise binlog, then there wouldn't be a issue.

cPanel runs mysql_install_db in its automatic upgrade scripts (dangerous already, automatically upgrading MySQL Server on a system!), it's run every night on cPanel systems even if no upgrade is done, and it behaves exactly as described above. It then chowns the binlog files to mysql:mysql which is of course …