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mk-config-diff.1p - Man Page

Diff MySQL configuration files and server variables.


Usage: mk-config-diff [OPTION...] CONFIG CONFIG [CONFIG...]

mk-config-diff diffs MySQL configuration files and server variables. CONFIG can be a filename or a DSN.  At least two CONFIG sources must be given. Like standard Unix diff, there is no output if there are no differences.

Diff host1 config from SHOW VARIABLES against host2:

  mk-config-diff h=host1 h=host2

Diff config from [mysqld] section in my.cnf against host1 config:

  mk-config-diff /etc/my.cnf h=host1

Diff the [mysqld] section of two option files:

   mk-config-diff /etc/my-small.cnf /etc/my-large.cnf


The following section is included to inform users about the potential risks, whether known or unknown, of using this tool.  The two main categories of risks are those created by the nature of the tool (e.g. read-only tools vs. read-write tools) and those created by bugs.

mk-config-diff reads MySQL's configuration and examines it and is thus very low risk.

At the time of this release there are no known bugs that pose a serious risk.

The authoritative source for updated information is always the online issue tracking system.  Issues that affect this tool will be marked as such.  You can see a list of such issues at the following URL: <http://www.maatkit.org/bugs/mk-config-diff>.

See also "Bugs" for more information on filing bugs and getting help.


mk-config-diff diffs MySQL configurations by examining the values of server system variables from two or more CONFIG sources specified on the command line.  A CONFIG source can be a DSN or a filename containing the output of mysqld --help --verbose, my_print_defaults, SHOW VARIABLES, or an option file (e.g. my.cnf).

For each DSN CONFIG, mk-config-diff connects to MySQL and gets variables and values by executing SHOW /*!40103 GLOBAL*/ VARIABLES.  This is an "active config" because it shows what server values MySQL is actively (currently) running with.

Only variables that all CONFIG sources have are compared because if a variable is not present then we cannot know or safely guess its value. For example, if you compare an option file (e.g. my.cnf) to an active config (i.e. SHOW VARIABLES from a DSN CONFIG), the option file will probably only have a few variables, whereas the active config has every variable. Only values of the variables present in both configs are compared.

Option file and DSN configs provide the best results.


There is no output when there are no differences.  When there are differences, mk-config-diff prints a report to STDOUT that looks similar to the following:

  2 config differences
  Variable                  my.master.cnf   my.slave.cnf
  ========================= =============== ===============
  datadir                   /tmp/12345/data /tmp/12346/data
  port                      12345           12346

Comparing MySQL variables is difficult because there are many variations and subtleties across the many versions and distributions of MySQL.  When a comparison fails, the tool prints a warning to STDERR, such as the following:

  Comparing log_error values (mysqld.log, /tmp/12345/data/mysqld.log)
  caused an error: Argument "/tmp/12345/data/mysqld.log" isn't numeric
  in numeric eq (==) at ./mk-config-diff line 2311.

Please report these warnings so the comparison functions can be improved.

Exit Status

mk-config-diff exits with a zero exit status when there are no differences, and 1 if there are.


This tool accepts additional command-line arguments.  Refer to the "Synopsis" and usage information for details.


Prompt for a password when connecting to MySQL.


short form: -A; type: string

Default character set.  If the value is utf8, sets Perl's binmode on STDOUT to utf8, passes the mysql_enable_utf8 option to DBD::mysql, and runs SET NAMES UTF8 after connecting to MySQL.  Any other value sets binmode on STDOUT without the utf8 layer, and runs SET NAMES after connecting to MySQL.


type: Array

Read this comma-separated list of config files; if specified, this must be the first option on the command line.  (This option does not specify a CONFIG; it's equivalent to --defaults-file.)


Fork to the background and detach from the shell.  POSIX operating systems only.


short form: -F; type: string

Only read mysql options from the given file.  You must give an absolute pathname.


Show help and exit.


short form: -h; type: string

Connect to host.


type: array

Ignore, do not compare, these variables.


short form: -p; type: string

Password to use for connection.


type: string

Create the given PID file when daemonized.  The file contains the process ID of the daemonized instance.  The PID file is removed when the daemonized instance exits.  The program checks for the existence of the PID file when starting; if it exists and the process with the matching PID exists, the program exits.


short form: -P; type: int

Port number to use for connection.


default: yes

Print the MySQL config diff report to STDOUT.  If you just want to check if the given configs are different or not by examining the tool's exit status, then specify --no-report to suppress the report.


type: int; default: 78

Truncate report lines to this many characters.  Since some variable values can be long, or when comparing multiple configs, it may help to increase the report width so values are not truncated beyond readability.


type: string; default: wait_timeout=10000

Set these MySQL variables.  Immediately after connecting to MySQL, this string will be appended to SET and executed.


short form: -S; type: string

Socket file to use for connection.


short form: -u; type: string

MySQL user if not current user.


Show version and exit.

DSN Options

These DSN options are used to create a DSN.  Each option is given like option=value.  The options are case-sensitive, so P and p are not the same option.  There cannot be whitespace before or after the = and if the value contains whitespace it must be quoted.  DSN options are comma-separated.  See the maatkit manpage for full details.


You can download Maatkit from Google Code at <http://code.google.com/p/maatkit/>, or you can get any of the tools easily with a command like the following:

   wget http://www.maatkit.org/get/toolname
   wget http://www.maatkit.org/trunk/toolname

Where toolname can be replaced with the name (or fragment of a name) of any of the Maatkit tools.  Once downloaded, they're ready to run; no installation is needed.  The first URL gets the latest released version of the tool, and the second gets the latest trunk code from Subversion.


The environment variable MKDEBUG enables verbose debugging output in all of the Maatkit tools:

   MKDEBUG=1 mk-....

System Requirements

You need the following Perl modules: DBI and DBD::mysql.


For a list of known bugs see <http://www.maatkit.org/bugs/mk-config-diff>.

Please use Google Code Issues and Groups to report bugs or request support: <http://code.google.com/p/maatkit/>.  You can also join #maatkit on Freenode to discuss Maatkit.

Please include the complete command-line used to reproduce the problem you are seeing, the version of all MySQL servers involved, the complete output of the tool when run with "--version", and if possible, debugging output produced by running with the MKDEBUG=1 environment variable.

Copyright, License and Warranty

This program is copyright 2009-2011 Percona Inc. Feedback and improvements are welcome.


This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2; OR the Perl Artistic License.  On UNIX and similar systems, you can issue `man perlgpl' or `man perlartistic' to read these licenses.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.


Baron Schwartz, Daniel Nichter

About Maatkit

This tool is part of Maatkit, a toolkit for power users of MySQL.  Maatkit was created by Baron Schwartz; Baron and Daniel Nichter are the primary code contributors.  Both are employed by Percona.  Financial support for Maatkit development is primarily provided by Percona and its clients.


This manual page documents Ver 1.0.0 Distrib 7540 $Revision: 7477 $.


2024-01-25 perl v5.38.2 User Contributed Perl Documentation