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mysqld_safe is the recommended way to start a mysqld server on Unix. mysqld_safe adds some safety features such as restarting the server when an error occurs and logging runtime information to an error log file. A description of error logging is given later in this section.
mysqld_safe tries to start an executable named mysqld. To override the default behavior and specify explicitly
the name of the server you want to run, specify a --mysqld
or --mysqld-version
option to mysqld_safe. You can also use --ledir
to indicate the directory where mysqld_safe should look for the server.
Many of the options to mysqld_safe are the same as the options to mysqld. See Section 5.1.3, "Server Command Options".
Options unknown to mysqld_safe
are passed to mysqld if they are specified on the command line, but
ignored if they are specified in the [mysqld_safe]
group of an option file. See Section 4.2.3.3,
"Using Option Files".
mysqld_safe reads all options from the [mysqld]
,
[server]
, and [mysqld_safe]
sections in option files.
For example, if you specify a [mysqld]
section like this, mysqld_safe will find and use the --log-error
option:
[mysqld]log-error=error.log
For backward compatibility, mysqld_safe also reads [safe_mysqld]
sections, although you should rename such sections to [mysqld_safe]
in MySQL 5.6 installations.
mysqld_safe supports the following options. It also reads option files and supports the options for processing them described at Section 4.2.3.4, "Command-Line Options that Affect Option-File Handling".
Table 4.1. mysqld_safe
Options
Format | Option File | Description |
---|---|---|
--basedir=path | basedir | The path to the MySQL installation directory |
--core-file-size=size | core-file-size | The size of the core file that mysqld should be able to create |
--datadir=path | datadir | The path to the data directory |
--defaults-extra-file=path | defaults-extra-file | The name of an option file to be read in addition to the usual option files |
--defaults-file=file_name | defaults-file | The name of an option file to be read instead of the usual option files |
--help | Display a help message and exit | |
--ledir=path | ledir | Use this option to indicate the path name to the directory where the server is located |
--log-error=file_name | log-error | Write the error log to the given file |
--malloc-lib=[lib-name] | malloc-lib | Alternative malloc library to use for mysqld |
--mysqld=prog_name | mysqld | The name of the server program (in the ledir directory) that you want to start |
--mysqld-version=suffix | mysqld-version | This option is similar to the --mysqld option, but you specify only the suffix for the server program name |
--nice=priority | nice | Use the nice program to set the server's scheduling priority to the given value |
--no-defaults | no-defaults | Do not read any option files |
--open-files-limit=count | open-files-limit | The number of files that mysqld should be able to open |
--pid-file=file_name | pid-file=file_name | The path name of the process ID file |
--plugin-dir=path | plugin-dir=path | The directory where plugins are located |
--port=number | port | The port number that the server should use when listening for TCP/IP connections |
--skip-kill-mysqld | skip-kill-mysqld | Do not try to kill stray mysqld processes |
--skip-syslog | skip-syslog | Do not write error messages to syslog; use error log file |
--socket=path | socket | The Unix socket file that the server should use when listening for local connections |
--syslog | syslog | Write error messages to syslog |
--syslog-tag=tag | syslog-tag | Tag suffix for messages written to syslog |
--timezone=timezone | timezone | Set the TZ time zone environment variable to the given option value |
--user={user_name|user_id} | user | Run the mysqld server as the user having the name user_name or the numeric user ID user_id |
Display a help message and exit.
The path to the MySQL installation directory.
The size of the core file that mysqld should be able to create. The option value is passed to ulimit -c.
The path to the data directory.
The name of an option file to be read in addition to the usual option files. This must be the first option on the command line if it is used. If the file does not exist or is otherwise inaccessible, the server will exit with an error.
The name of an option file to be read instead of the usual option files. This must be the first option on the command line if it is used.
If mysqld_safe cannot find the server, use this option to indicate the path name to the directory where the server is located.
Write the error log to the given file. See Section 5.2.2, "The Error Log".
The name of the library to use for memory allocation instead of the system malloc()
library. Any library can be used by specifying its path name, but there is a shortcut form to enable
use of the tcmalloc
library that is shipped with binary MySQL
distributions for Linux in MySQL 5.6.
The --malloc-lib
option works by modifying the LD_PRELOAD
environment value to affect
dynamic linking to enable the loader to find the memory-allocation library when mysqld runs:
If the option is not given, or is given without a value (--malloc-lib=
),
LD_PRELOAD
is not modified and no attempt is made to use tcmalloc
.
If the option is given as --malloc-lib=tcmalloc
, mysqld_safe looks for a tcmalloc
library in /usr/lib
and
then in the MySQL pkglibdir
location (for example, /usr/local/mysql/lib
or whatever is appropriate). If tmalloc
is found, its path name is added to the beginning of
the LD_PRELOAD
value for mysqld. If tcmalloc
is not found, mysqld_safe aborts with an error.
If the option is given as --malloc-lib=
, that full path
is added to the beginning of the /path/to/some/library
LD_PRELOAD
value. If the full
path points to a nonexistent or unreadable file, mysqld_safe aborts with an error.
For cases where mysqld_safe adds a path name to LD_PRELOAD
, it adds the path to the beginning of any existing
value the variable already has.
Linux users can use the libtcmalloc_minimal.so
included in binary
packages by adding these lines to the my.cnf
file:
[mysqld_safe]malloc-lib=tcmalloc
Those lines also suffice for users on any platform who have installed a tcmalloc
package in /usr/lib
. To use a specific tcmalloc
library, specify its full path name. Example:
[mysqld_safe]malloc-lib=/opt/lib/libtcmalloc_minimal.so
The name of the server program (in the ledir
directory) that you want
to start. This option is needed if you use the MySQL binary distribution but have the data directory
outside of the binary distribution. If mysqld_safe cannot find the server, use the --ledir
option to indicate the path name to the directory where
the server is located.
This option is similar to the --mysqld
option, but you specify only the suffix for the server
program name. The basename is assumed to be mysqld. For example, if you use --mysqld-version=debug
, mysqld_safe starts the mysqld-debug program in the ledir
directory. If the argument to --mysqld-version
is empty, mysqld_safe uses mysqld in the ledir
directory.
Use the nice
program to set the server's scheduling priority to the
given value.
Do not read any option files. This must be the first option on the command line if it is used.
The number of files that mysqld
should be able to open. The option value is passed to ulimit
-n. Note that you need to start mysqld_safe as root
for this to work properly!
The path name of the process ID file.
The path name of the plugin directory.
The port number that the server should use when listening for TCP/IP connections. The port number
must be 1024 or higher unless the server is started by the root
system
user.
Do not try to kill stray mysqld processes at startup. This option works only on Linux.
The Unix socket file that the server should use when listening for local connections.
--syslog
causes error messages to be sent to syslog
on systems that support the logger program. --skip-syslog
suppresses the use of syslog
; messages are written to an error log file.
When syslog
is used, the daemon.err
syslog
priority/facility is used for all log messages.
For logging to syslog
, messages from mysqld_safe and mysqld are written with a tag of mysqld_safe
and mysqld
, respectively. To
specify a suffix for the tag, use --syslog-tag=
, which
modifies the tags to be tag
mysqld_safe-
and tag
mysqld-
. tag
Set the TZ
time zone environment variable to the given option value.
Consult your operating system documentation for legal time zone specification formats.
Run the mysqld server as the user having the name user_name
or the numeric user ID user_id
. ("User" in this context refers to a system login account, not a MySQL
user listed in the grant tables.)
If you execute mysqld_safe
with the --defaults-file
or --defaults-extra-file
option to name an option file, the option must be the first one given on the command line or the option file
will not be used. For example, this command will not use the named option file:
mysql> mysqld_safe --port=port_num
--defaults-file=file_name
Instead, use the following command:
mysql> mysqld_safe --defaults-file=file_name
--port=port_num
The mysqld_safe script is written so that it normally can start a server that was installed from either a source or a binary distribution of MySQL, even though these types of distributions typically install the server in slightly different locations. (See Section 2.1.5, "Installation Layouts".) mysqld_safe expects one of the following conditions to be true:
The server and databases can be found relative to the working directory (the
directory from which mysqld_safe is invoked). For binary distributions,
mysqld_safe looks under its working directory for
bin
and data
directories. For source
distributions, it looks for libexec
and var
directories. This condition should be met if you execute mysqld_safe from your MySQL installation directory
(for example, /usr/local/mysql
for a binary distribution).
If the server and databases cannot be found relative to the working directory, mysqld_safe attempts to locate them by absolute path
names. Typical locations are /usr/local/libexec
and /usr/local/var
. The actual locations are determined from the values
configured into the distribution at the time it was built. They should be correct if MySQL is installed
in the location specified at configuration time.
Because mysqld_safe tries to find the server and databases relative to its own working directory, you can install a binary distribution of MySQL anywhere, as long as you run mysqld_safe from the MySQL installation directory:
shell>cd
shell>mysql_installation_directory
bin/mysqld_safe &
If mysqld_safe fails, even when invoked from the MySQL installation
directory, you can specify the --ledir
and --datadir
options to indicate the directories in which the server and
databases are located on your system.
In MySQL 5.6.5 and later, mysqld_safe tries to use the sleep and date system utilities to determine how many times it has attempted to start this second, and—if these are present and this is greater than 5 times—is forced to wait 1 full second before starting again. This is intended to prevent excessive CPU usage in the event of repeated failures. (Bug #11761530, Bug #54035)
When you use mysqld_safe to start mysqld, mysqld_safe arranges for error (and notice) messages from itself and from mysqld to go to the same destination.
There are several mysqld_safe options for controlling the destination of these messages:
--syslog
:
Write error messages to syslog
on systems that support the logger program.
--skip-syslog
:
Do not write error messages to syslog
. Messages are written to the default
error log file (
in
the data directory), or to a named file if the host_name
.err--log-error
option is given.
--log-error=
: Write
error messages to the named error file.file_name
If none of these options is given, the default is --skip-syslog
.
If --syslog
and
--log-error
are both given, a warning is issued and --log-error
takes precedence.
When mysqld_safe writes a message, notices go to the logging
destination (syslog
or the error log file) and stdout
.
Errors go to the logging destination and stderr
.
Normally, you should not edit the mysqld_safe script. Instead, configure mysqld_safe by using command-line options or options in the
[mysqld_safe]
section of a my.cnf
option file. In
rare cases, it might be necessary to edit mysqld_safe to get it to start the server properly. However,
if you do this, your modified version of mysqld_safe might be overwritten if you upgrade MySQL in the
future, so you should make a copy of your edited version that you can reinstall.