mysqld_multi - Online in the Cloud

PROGRAM:

NAME

mysqld_multi - manage multiple MySQL servers

SYNOPSIS

mysqld_multi [options] {start|stop|report} [GNR[,GNR] ...]

DESCRIPTION

mysqld_multi is designed to manage several mysqld processes that listen for connections on
different Unix socket files and TCP/IP ports. It can start or stop servers, or report
their current status.

mysqld_multi searches for groups named [mysqldN] in my.cnf (or in the file named by the
--defaults-file option). N can be any positive integer. This number is referred to in the
following discussion as the option group number, or GNR. Group numbers distinguish option
groups from one another and are used as arguments to mysqld_multi to specify which servers
you want to start, stop, or obtain a status report for. Options listed in these groups are
the same that you would use in the [mysqld] group used for starting mysqld. (See, for
example, Section 2.10.1.2, “Starting and Stopping MySQL Automatically”.) However, when
using multiple servers, it is necessary that each one use its own value for options such
as the Unix socket file and TCP/IP port number. For more information on which options must
be unique per server in a multiple-server environment, see Section 5.3, “Running Multiple
MySQL Instances on One Machine”.

To invoke mysqld_multi, use the following syntax:

shell> mysqld_multi [options] {start|stop|reload|report} [GNR[,GNR] ...]

start, stop, reload (stop and restart), and report indicate which operation to perform.
(reload is available as of MySQL 5.6.3.) You can perform the designated operation for a
single server or multiple servers, depending on the GNR list that follows the option name.
If there is no list, mysqld_multi performs the operation for all servers in the option
file.

Each GNR value represents an option group number or range of group numbers. The value
should be the number at the end of the group name in the option file. For example, the GNR
for a group named [mysqld17] is 17. To specify a range of numbers, separate the first and
last numbers by a dash. The GNR value 10-13 represents groups [mysqld10] through
[mysqld13]. Multiple groups or group ranges can be specified on the command line,
separated by commas. There must be no whitespace characters (spaces or tabs) in the GNR
list; anything after a whitespace character is ignored.

This command starts a single server using option group [mysqld17]:

shell> mysqld_multi start 17

This command stops several servers, using option groups [mysqld8] and [mysqld10] through
[mysqld13]:

shell> mysqld_multi stop 8,10-13

For an example of how you might set up an option file, use this command:

shell> mysqld_multi --example

mysqld_multi searches for option files as follows:

· With --no-defaults, no option files are read.

· With --defaults-file=file_name, only the named file is read.

· Otherwise, option files in the standard list of locations are read, including any file
named by the --defaults-extra-file=file_name option, if one is given. (If the option
is given multiple times, the last value is used.)

Option files read are searched for [mysqld_multi] and [mysqldN] option groups. The
[mysqld_multi] group can be used for options to mysqld_multi itself. [mysqldN] groups can
be used for options passed to specific mysqld instances.

The [mysqld] or [mysqld_safe] groups can be used for common options read by all instances
of mysqld or mysqld_safe. You can specify a --defaults-file=file_name option to use a
different configuration file for that instance, in which case the [mysqld] or
[mysqld_safe] groups from that file will be used for that instance.

mysqld_multi supports the following options.

· --help

Display a help message and exit.

· --example

Display a sample option file.

· --log=file_name

Specify the name of the log file. If the file exists, log output is appended to it.

· --mysqladmin=prog_name

The mysqladmin binary to be used to stop servers.

· --mysqld=prog_name

The mysqld binary to be used. You can specify mysqld_safe as the value for this
option. If you use mysqld_safe to start the server, you can include the mysqld or
ledir options in the corresponding [mysqldN] option group. These options indicate the
name of the server that mysqld_safe should start and the path name of the directory
where the server is located. (See the descriptions for these options in
mysqld_safe(1).) Example:

[mysqld38]
mysqld = mysqld-debug
ledir = /opt/local/mysql/libexec

· --no-log

Print log information to stdout rather than to the log file. By default, output goes
to the log file.

· --password=password

The password of the MySQL account to use when invoking mysqladmin. The password value
is not optional for this option, unlike for other MySQL programs.

· --silent

Silent mode; disable warnings.

· --tcp-ip

Connect to each MySQL server through the TCP/IP port instead of the Unix socket file.
(If a socket file is missing, the server might still be running, but accessible only
through the TCP/IP port.) By default, connections are made using the Unix socket file.
This option affects stop and report operations.

· --user=user_name

The user name of the MySQL account to use when invoking mysqladmin.

· --verbose

Be more verbose.

· --version

Display version information and exit.

Some notes about mysqld_multi:

· Most important: Before using mysqld_multi be sure that you understand the meanings of
the options that are passed to the mysqld servers and why you would want to have
separate mysqld processes. Beware of the dangers of using multiple mysqld servers with
the same data directory. Use separate data directories, unless you know what you are
doing. Starting multiple servers with the same data directory does not give you extra
performance in a threaded system. See Section 5.3, “Running Multiple MySQL Instances
on One Machine”.

·

Important
Make sure that the data directory for each server is fully accessible to the Unix
account that the specific mysqld process is started as. Do not use the Unix root
account for this, unless you know what you are doing. See Section 6.1.5, “How to
Run MySQL as a Normal User”.

· Make sure that the MySQL account used for stopping the mysqld servers (with the
mysqladmin program) has the same user name and password for each server. Also, make
sure that the account has the SHUTDOWN privilege. If the servers that you want to
manage have different user names or passwords for the administrative accounts, you
might want to create an account on each server that has the same user name and
password. For example, you might set up a common multi_admin account by executing the
following commands for each server:

shell> mysql -u root -S /tmp/mysql.sock -p
Enter password:
mysql> GRANT SHUTDOWN ON *.*
-> TO 'multi_admin'@'localhost' IDENTIFIED BY 'multipass';

See Section 6.2, “The MySQL Access Privilege System”. You have to do this for each
mysqld server. Change the connection parameters appropriately when connecting to each
one. The host name part of the account name must permit you to connect as multi_admin
from the host where you want to run mysqld_multi.

· The Unix socket file and the TCP/IP port number must be different for every mysqld.
(Alternatively, if the host has multiple network addresses, you can use --bind-address
to cause different servers to listen to different interfaces.)

· The --pid-file option is very important if you are using mysqld_safe to start mysqld
(for example, --mysqld=mysqld_safe) Every mysqld should have its own process ID file.
The advantage of using mysqld_safe instead of mysqld is that mysqld_safe monitors its
mysqld process and restarts it if the process terminates due to a signal sent using
kill -9 or for other reasons, such as a segmentation fault. The mysqld_safe script
might require that you start it from a certain place. This means that you might have
to change location to a certain directory before running mysqld_multi. If you have
problems starting, please see the mysqld_safe script. Check especially the lines:

----------------------------------------------------------------
MY_PWD=`pwd`
# Check if we are starting this relative (for the binary release)
if test -d $MY_PWD/data/mysql -a \
-f ./share/mysql/english/errmsg.sys -a \
-x ./bin/mysqld
----------------------------------------------------------------

The test performed by these lines should be successful, or you might encounter
problems. See mysqld_safe(1).

· You might want to use the --user option for mysqld, but to do this you need to run the
mysqld_multi script as the Unix superuser (root). Having the option in the option file
doesn't matter; you just get a warning if you are not the superuser and the mysqld
processes are started under your own Unix account.

The following example shows how you might set up an option file for use with mysqld_multi.
The order in which the mysqld programs are started or stopped depends on the order in
which they appear in the option file. Group numbers need not form an unbroken sequence.
The first and fifth [mysqldN] groups were intentionally omitted from the example to
illustrate that you can have “gaps” in the option file. This gives you more flexibility.

# This file should probably be in your home dir (~/.my.cnf)
# or /etc/my.cnf
# Version 2.1 by Jani Tolonen
[mysqld_multi]
mysqld = /usr/local/bin/mysqld_safe
mysqladmin = /usr/local/bin/mysqladmin
user = multi_admin
password = multipass
[mysqld2]
socket = /tmp/mysql.sock2
port = 3307
pid-file = /usr/local/mysql/var2/hostname.pid2
datadir = /usr/local/mysql/var2
language = /usr/local/share/mysql/english
user = john
[mysqld3]
socket = /tmp/mysql.sock3
port = 3308
pid-file = /usr/local/mysql/var3/hostname.pid3
datadir = /usr/local/mysql/var3
language = /usr/local/share/mysql/swedish
user = monty
[mysqld4]
socket = /tmp/mysql.sock4
port = 3309
pid-file = /usr/local/mysql/var4/hostname.pid4
datadir = /usr/local/mysql/var4
language = /usr/local/share/mysql/estonia
user = tonu
[mysqld6]
socket = /tmp/mysql.sock6
port = 3311
pid-file = /usr/local/mysql/var6/hostname.pid6
datadir = /usr/local/mysql/var6
language = /usr/local/share/mysql/japanese
user = jani

See Section 4.2.6, “Using Option Files”.

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This documentation is free software; you can redistribute it and/or modify it only under
the terms of the GNU General Public License as published by the Free Software Foundation;
version 2 of the License.

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PURPOSE. See the GNU General Public License for more details.

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Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/.

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