MySQL Bugs: #3581: binary log dir defaults to default data dir

Bug #3581	binary log dir defaults to default data dir
Submitted:	27 Apr 2004 16:07	Modified:	30 Apr 2004 15:31
Reporter:	John Wobus	Email Updates:
Status:	Not a Bug	Impact on me:	None
Category:	MySQL Server: Installing	Severity:	S3 (Non-critical)
Version:	4.015	OS:	Solaris (Solaris 8)
Assigned to:	Guilhem Bichot	CPU Architecture:	Any

Description:
If the binary log is enabled but no directory is specified, mysqld puts the log files in the default data 
directory as incorporated in the build.  The reference manual states that mysqld puts the log files in the 
data directory.  If the data directory is set, then this will not match.

It is possible that this only occurs under certain combinations of command line and my.cnf 
configurations, e.g. my.cnf includes the mysqld line 'log-bin' and the command line specifies a data 
directory.

How to repeat:

Hello,

I have tried what was suggested: "my.cnf includes the mysqld line 'log-bin' and the command line specifies a data directory" and the binary logs were still created in the directory specified in --datadir in the command line.
So I can't repeat the problem. And looking at the code, I can't understand how this could happen. Could you please provide detailed instructions explaining what you do to repeat the problem?
Thank you.
Guilhem

User was confused by the fact that if datadir is specified in my.cnf, and --log-bin (no argument) is used on the command line then the binlog is created in the datadir, whereas if the datadir is not specified in my.cnf then it is created in the specified-at-build-time datadir.
To avoid usage of any my.cnf by mysqld (or other MySQL programs), solution is to use --no-defaults (as the first option).

I tracked my log-bin problem to two mysqld behaviors, one of which I found documented in my
O'Reilly 2002 edition of the reference manual. As I suspected might be the case, the behaviors involve
the use of my.cnf along with the command line.

The behavior that is documented is the exact location of DATADIR/my.cnf. Specifically, O'Reilly in 4.1.2
(page 218) says:

"DATADIR is the MySQL data directory (typically /usr/local/mysql/data for a binary installation or /usr/
local/var for a source installation). Note that this is the directory that was specified at configuration
time, not the one specified with --datadir when mysqld starts up! ) --datadir has no effect on where
the server looks for option files because it looks for them before it processes any command-line
arguments)."

I can imagine how this simplifies the program logic. But I suggest that referring to the config file's
location as DATADIR/my.cnf is misleading. The location is "DATADIR/my.cnf" under certain conditions,
but under other conditions, it is not.

The other behavior that confused me is this: when I put "--log-bin=foo" on the command line,
expecting this to override whatever the my.cnf files say about binary logging, it does so. However,
when I use just "--log-bin", expecting mysqld to use the default path, DATADIR/HOSTNAME-bin, then I
find mysqld does indeed log but if a my.cnf is specifying a filename or path, it uses that one.

Once again, I can imagine doing otherwise would complicate the programming logic as well as the
user's mental model of how variables are set in general, but it misled me. I set the command line
parameters to do what I needed and found mysqld using values I didn't even realize it would look for.
Through the combination of these two behaviors, it took me a while to figure out what was going on.

John Wobus