http://dev.mysql.com/doc/refman/5.5/en//mysqld-safe.html
4.3.2. mysqld_safe — MySQL Server Startup Script
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
sections, although you should rename such sections to
[safe_mysqld]
in MySQL 5.5 installations.
[mysqld_safe]
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 | Introduced |
---|---|---|---|
--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 | 5.5.3 |
--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 | 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 5.5.
The
--malloc-lib
option works by modifying the
environment value to affect dynamic linking to enable the loader to find the memory-allocation library when
LD_PRELOAD
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
library in
tcmalloc/usr/lib
and then in the MySQL
pkglibdir
location (for example,
or whatever is appropriate). If
/usr/local/mysql/lib
is found, its path name is added to the beginning of the
tmalloc
value for
LD_PRELOAD
mysqld. If
is not found,
tcmalloc
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
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
ledir
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
directory. If the argument to
ledir
--mysqld-version
is empty,
mysqld_safe uses
mysqld in the
directory.
ledir -
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
for this to work properly!
root -
The path name of the process ID file.
-
The path name of the plugin directory. This option was added in MySQL 5.5.3.
-
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
andmysqld
, respectively. To specify a suffix for the tag, use
--syslog-tag=
, which modifies the tags to betag
mysqld_safe-
andtag
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
anddata
directories. For source distributions, it looks for
libexec
andvar
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 mysql_installation_directory
shell> 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.
Beginning with MySQL 5.5.21,
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 thehost_name
.err
--log-error
option is given. -
--log-error=
:file_name
Write error messages to the named error file.
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.