Provided by: mysql-server-core-8.0_8.0.41-0ubuntu0.22.04.1_amd64 
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.
Note
For some Linux platforms, MySQL installation from RPM or Debian packages includes systemd support for
managing MySQL server startup and shutdown. On these platforms, mysqld_multi is not installed because
it is unnecessary. For information about using systemd to handle multiple MySQL instances, see
Section 2.5.9, “Managing MySQL Server with systemd”.
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 2.9.5, “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 7.8, “Running Multiple MySQL Instances on One Machine”.
To invoke mysqld_multi, use the following syntax:
mysqld_multi [options] {start|stop|reload|report} [GNR[,GNR] ...]
start, stop, reload (stop and restart), and report indicate which operation to perform. 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]:
mysqld_multi start 17
This command stops several servers, using option groups [mysqld8] and [mysqld10] through [mysqld13]:
mysqld_multi stop 8,10-13
For an example of how you might set up an option file, use this command:
mysqld_multi --example
mysqld_multi searches for option files as follows:
• With --no-defaults, no option files are read.
┌────────────────────┬───────────────┐
│Command-Line Format │ --no-defaults │
├────────────────────┼───────────────┤
│Type │ Boolean │
├────────────────────┼───────────────┤
│Default Value │ false │
└────────────────────┴───────────────┘
• With --defaults-file=file_name, only the named file is read.
┌────────────────────┬──────────────────────────┐
│Command-Line Format │ --defaults-file=filename │
├────────────────────┼──────────────────────────┤
│Type │ File name │
├────────────────────┼──────────────────────────┤
│Default Value │ [none] │
└────────────────────┴──────────────────────────┘
• 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.)
┌────────────────────┬────────────────────────────────┐
│Command-Line Format │ --defaults-extra-file=filename │
├────────────────────┼────────────────────────────────┤
│Type │ File name │
├────────────────────┼────────────────────────────────┤
│Default Value │ [none] │
└────────────────────┴────────────────────────────────┘
For additional information about these and other option-file options, see Section 6.2.2.3, “Command-Line
Options that Affect Option-File Handling”.
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 are used for that
instance.
mysqld_multi supports the following options.
• --help
┌────────────────────┬─────────┐
│Command-Line Format │ --help │
├────────────────────┼─────────┤
│Type │ Boolean │
├────────────────────┼─────────┤
│Default Value │ false │
└────────────────────┴─────────┘
Display a help message and exit.
• --example
┌────────────────────┬───────────┐
│Command-Line Format │ --example │
├────────────────────┼───────────┤
│Type │ Boolean │
├────────────────────┼───────────┤
│Default Value │ false │
└────────────────────┴───────────┘
Display a sample option file.
• --log=file_name
┌────────────────────┬───────────────────────────┐
│Command-Line Format │ --log=path │
├────────────────────┼───────────────────────────┤
│Type │ File name │
├────────────────────┼───────────────────────────┤
│Default Value │ /var/log/mysqld_multi.log │
└────────────────────┴───────────────────────────┘
Specify the name of the log file. If the file exists, log output is appended to it.
• --mysqladmin=prog_name
┌────────────────────┬───────────────────┐
│Command-Line Format │ --mysqladmin=file │
├────────────────────┼───────────────────┤
│Type │ File name │
├────────────────────┼───────────────────┤
│Default Value │ [none] │
└────────────────────┴───────────────────┘
The mysqladmin binary to be used to stop servers.
• --mysqld=prog_name
┌────────────────────┬───────────────┐
│Command-Line Format │ --mysqld=file │
├────────────────────┼───────────────┤
│Type │ File name │
├────────────────────┼───────────────┤
│Default Value │ [none] │
└────────────────────┴───────────────┘
The mysqld binary to be used. Note that you can specify mysqld_safe as the value for this option
also. 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
┌────────────────────┬──────────┐
│Command-Line Format │ --no-log │
├────────────────────┼──────────┤
│Type │ Boolean │
├────────────────────┼──────────┤
│Default Value │ false │
└────────────────────┴──────────┘
Print log information to stdout rather than to the log file. By default, output goes to the log file.
• --password=password
┌────────────────────┬───────────────────┐
│Command-Line Format │ --password=string │
├────────────────────┼───────────────────┤
│Type │ String │
├────────────────────┼───────────────────┤
│Default Value │ [none] │
└────────────────────┴───────────────────┘
The password of the MySQL account to use when invoking mysqladmin. Note that the password value is
not optional for this option, unlike for other MySQL programs.
• --silent
┌────────────────────┬──────────┐
│Command-Line Format │ --silent │
├────────────────────┼──────────┤
│Type │ Boolean │
├────────────────────┼──────────┤
│Default Value │ false │
└────────────────────┴──────────┘
Silent mode; disable warnings.
• --tcp-ip
┌────────────────────┬──────────┐
│Command-Line Format │ --tcp-ip │
├────────────────────┼──────────┤
│Type │ Boolean │
├────────────────────┼──────────┤
│Default Value │ false │
└────────────────────┴──────────┘
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
┌────────────────────┬─────────────┐
│Command-Line Format │ --user=name │
├────────────────────┼─────────────┤
│Type │ String │
├────────────────────┼─────────────┤
│Default Value │ root │
└────────────────────┴─────────────┘
The user name of the MySQL account to use when invoking mysqladmin.
• --verbose
┌────────────────────┬───────────┐
│Command-Line Format │ --verbose │
├────────────────────┼───────────┤
│Type │ Boolean │
├────────────────────┼───────────┤
│Default Value │ false │
└────────────────────┴───────────┘
Be more verbose.
• --version
┌────────────────────┬───────────┐
│Command-Line Format │ --version │
├────────────────────┼───────────┤
│Type │ Boolean │
├────────────────────┼───────────┤
│Default Value │ false │
└────────────────────┴───────────┘
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 7.8, “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 8.1.5, “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:
$> mysql -u root -S /tmp/mysql.sock -p
Enter password:
mysql> CREATE USER 'multi_admin'@'localhost' IDENTIFIED BY 'multipass';
mysql> GRANT SHUTDOWN ON *.* TO 'multi_admin'@'localhost';
See Section 8.2, “Access Control and Account Management”. You have to do this for each mysqld server.
Change the connection parameters appropriately when connecting to each one. Note that 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 set the bind_address system variable 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.
• 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 is an example of a my.cnf file for mysqld_multi.
# Usually this file is located in home dir ~/.my.cnf or /etc/my.cnf
[mysqld_multi]
mysqld = /usr/local/mysql/bin/mysqld_safe
mysqladmin = /usr/local/mysql/bin/mysqladmin
user = multi_admin
password = my_password
[mysqld2]
socket = /tmp/mysql.sock2
port = 3307
pid-file = /usr/local/mysql/data2/hostname.pid2
datadir = /usr/local/mysql/data2
language = /usr/local/mysql/share/mysql/english
user = unix_user1
[mysqld3]
mysqld = /path/to/mysqld_safe
ledir = /path/to/mysqld-binary/
mysqladmin = /path/to/mysqladmin
socket = /tmp/mysql.sock3
port = 3308
pid-file = /usr/local/mysql/data3/hostname.pid3
datadir = /usr/local/mysql/data3
language = /usr/local/mysql/share/mysql/swedish
user = unix_user2
[mysqld4]
socket = /tmp/mysql.sock4
port = 3309
pid-file = /usr/local/mysql/data4/hostname.pid4
datadir = /usr/local/mysql/data4
language = /usr/local/mysql/share/mysql/estonia
user = unix_user3
[mysqld6]
socket = /tmp/mysql.sock6
port = 3311
pid-file = /usr/local/mysql/data6/hostname.pid6
datadir = /usr/local/mysql/data6
language = /usr/local/mysql/share/mysql/japanese
user = unix_user4
See Section 6.2.2.2, “Using Option Files”.
COPYRIGHT
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This documentation is free software; you can redistribute it and/or modify it only under the terms of the
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This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.
You should have received a copy of the GNU General Public License along with the program; if not, write
to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see
http://www.gnu.org/licenses/.
SEE ALSO
For more information, please refer to the MySQL Reference Manual, which may already be installed locally
and which is also available online at http://dev.mysql.com/doc/.
AUTHOR
Oracle Corporation (http://dev.mysql.com/).