Bug #73750 mysqld_multi writes logfile to wrong directory
Submitted: 28 Aug 2014 8:13 Modified: 28 Aug 2014 9:46
Reporter: Hartmut Holzgraefe Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: Logging Severity:S3 (Non-critical)
Version:5.6.20, all? OS:Linux
Assigned to: CPU Architecture:Any

[28 Aug 2014 8:13] Hartmut Holzgraefe
Description:
If no datadir is set via option files or command line the log location defaults to:

  [...]
  if (!defined($logdir))
  {
    $logdir= "/usr/share/mysql" if (-d "/usr/share/mysql" && -w "/usr/share/mysql");
  }
  [...]

(or whatever the "share" path is for the current installation) in the init_log() function inside the script

This is a very unexpected location, and AFAICT in violation with the linux file system standard (and Unix practice in general) as /usr should be considered read-only for everything but software installation actions (so that a read-only /usr file system can be shared between multiple installations)

How to repeat:
Check source of installed mysqld_multi script or just use mysqld_multi with --no-defaults or the exampe my.cnf given in the script itself, then see that you have a "mysqld_multi.log" file in the same directory that the error message translations, charset information, and files like mysql_system_tables.sql are in 
(usually /usr/share/mysql or /usr/local/mysql/share ...) ... at least if the user executing mysqld_multi had sufficient permissions to write there ...

Suggested fix:
The default log location should be the default datadir, not pkgdatadir ...
[28 Aug 2014 9:46] Umesh Shastry
Hello Hartmut,

Thank you for the bug report.
Verifying based on code inspection.

Thanks,
Umesh
[28 Aug 2014 9:47] Umesh Shastry
// From my local repo

[ushastry@cluster-repo server]$ more mysql-5.0.96/bin/mysqld_multi |grep --color=auto -i logdir
my $logdir= undef();
      $logdir= $1;
  if (!defined($logdir))
    $logdir= "/usr/local/mysql/share" if (-d "/usr/local/mysql/share" && -w "/usr/local/mysql/share");
  if (!defined($logdir))
    $opt_log= "$logdir/mysqld_multi.log";
####        file will be read from $opt_logdir)
#### 2.arg: logfile -name (w2log assumes that the logfile is in $opt_logdir).
[ushastry@cluster-repo server]$
[ushastry@cluster-repo server]$ more mysql-5.1.73/bin/mysqld_multi |grep --color=auto -i logdir
my $logdir= undef();
      $logdir= $1;
  if (!defined($logdir))
    $logdir= "/usr/local/mysql/share" if (-d "/usr/local/mysql/share" && -w "/usr/local/mysql/share");
  if (!defined($logdir))
    $opt_log= "$logdir/mysqld_multi.log";
####        file will be read from $opt_logdir)
#### 2.arg: logfile -name (w2log assumes that the logfile is in $opt_logdir).
[ushastry@cluster-repo server]$
[ushastry@cluster-repo server]$ more mysql-5.5.40/bin/mysqld_multi |grep --color=auto -i logdir
my $logdir= undef();
      $logdir= $1;
  if (!defined($logdir))
    $logdir= "/usr/local/mysql/share" if (-d "/usr/local/mysql/share" && -w "/usr/local/mysql/share");
  if (!defined($logdir))
    $opt_log= "$logdir/mysqld_multi.log";
####        file will be read from $opt_logdir)
#### 2.arg: logfile -name (w2log assumes that the logfile is in $opt_logdir).
[ushastry@cluster-repo server]$
[ushastry@cluster-repo server]$ more mysql-advanced-5.6.21/bin/mysqld_multi |grep --color=auto -i logdir
my $logdir= undef();
      $logdir= $1;
  if (!defined($logdir))
    $logdir= "/usr/local/mysql/share" if (-d "/usr/local/mysql/share" && -w "/usr/local/mysql/share");
  if (!defined($logdir))
    $opt_log= "$logdir/mysqld_multi.log";
####        file will be read from $opt_logdir)
#### 2.arg: logfile -name (w2log assumes that the logfile is in $opt_logdir).
[ushastry@cluster-repo server]$
[ushastry@cluster-repo server]$
[ushastry@cluster-repo server]$
[ushastry@cluster-repo server]$
[ushastry@cluster-repo server]$ more mysql-5.7.4/bin/mysqld_multi |grep --color=auto -i logdir
my $logdir= undef();
      $logdir= $1;
  if (!defined($logdir))
    $logdir= "/usr/local/mysql/share" if (-d "/usr/local/mysql/share" && -w "/usr/local/mysql/share");
  if (!defined($logdir))
    $opt_log= "$logdir/mysqld_multi.log";
####        file will be read from $opt_logdir)
#### 2.arg: logfile -name (w2log assumes that the logfile is in $opt_logdir).