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5.4.3 `mysqld_multi' -- Manage Multiple MySQL Servers
-----------------------------------------------------
`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. The MySQL
Instance Manager is an alternative means of managing multiple servers
(see instance-manager).
`mysqld_multi' searches for groups named `[mysqldN]' in `my.cnf' (or in
the file named by the -config-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,
automatic-start.) 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
multiple-servers.
To invoke `mysqld_multi', use the following syntax:
shell> mysqld_multi [OPTIONS] {start|stop|report} [GNR[,GNR] ...]
`start', `stop', 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]':
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' supports the following options:
* -help
Display a help message and exit.
* -config-file=NAME
Specify the name of an alternative option file. This affects where
`mysqld_multi' looks for `[mysqldN]' option groups. Without this
option, all options are read from the usual `my.cnf' file. The
option does not affect where `mysqld_multi' reads its own options,
which are always taken from the `[mysqld_multi]' group in the usual
`my.cnf' file.
* -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. 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 pathname of the directory where the server is
located. (See the descriptions for these options in
mysqld-safe.) Example:
[mysqld38]
mysqld = mysqld-max
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'. Note that 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 via 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 via 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 username 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
multiple-servers.
* *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
changing-mysql-user.
* Make sure that the MySQL account used for stopping the `mysqld'
servers (with the `mysqladmin' program) has the same username 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 usernames or passwords for the administrative accounts,
you might want to create an account on each server that has the
same username 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 privileges. You have to do this for each `mysqld'
server. Change the connection parameters appropriately when
connecting to each one. Note that the hostname part of the account
name must allow 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'.
* 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. Please note that 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.
* 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 `root'
user. 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 option-files.
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