6.3.2 mysqld_safe — MySQL 服务器启动脚本
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. A description of error logging is given later in this section.
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_safe is not installed because it is unnecessary. For more information, see Section 2.5.9, “Managing MySQL Server with systemd”.
One implication of the non-use of mysqld_safe on platforms that use systemd for server management is that use of [mysqld_safe]
or [safe_mysqld]
sections in option files is not supported and might lead to unexpected behavior.
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 7.1.7, “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 6.2.2.2, “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 finds and uses the --log-error
option:
[mysqld]
log-error=error.log
For backward compatibility, mysqld_safe also reads [safe_mysqld]
sections, but to be current you should rename such sections to [mysqld_safe]
.
mysqld_safe accepts options on the command line and in option files, as described in the following table. For information about option files used by MySQL programs, see Section 6.2.2.2, “Using Option Files”.
Table 6.7 mysqld_safe Options
Option Name | Description |
---|---|
--basedir | Path to MySQL installation directory |
--core-file-size | Size of core file that mysqld should be able to create |
--datadir | Path to data directory |
--defaults-extra-file | Read named option file in addition to usual option files |
--defaults-file | Read only named option file |
--help | Display help message and exit |
--ledir | Path to directory where server is located |
--log-error | Write error log to named file |
--malloc-lib | Alternative malloc library to use for mysqld |
--mysqld | Name of server program to start (in ledir directory) |
--mysqld-safe-log-timestamps | Timestamp format for logging |
--mysqld-version | Suffix for server program name |
--nice | Use nice program to set server scheduling priority |
--no-defaults | Read no option files |
--open-files-limit | Number of files that mysqld should be able to open |
--pid-file | Path name of server process ID file |
--plugin-dir | Directory where plugins are installed |
--port | Port number on which to listen for TCP/IP connections |
--skip-kill-mysqld | Do not try to kill stray mysqld processes |
--skip-syslog | Do not write error messages to syslog; use error log file |
--socket | Socket file on which to listen for Unix socket connections |
--syslog | Write error messages to syslog |
--syslog-tag | Tag suffix for messages written to syslog |
--timezone | Set TZ time zone environment variable to named value |
--user | Run mysqld as user having name user_name or numeric user ID user_id |
-
Command-Line Format --help
Display a help message and exit.
-
Command-Line Format --basedir=dir_name
Type Directory name The path to the MySQL installation directory.
-
Command-Line Format --core-file-size=size
Type String The size of the core file that mysqld should be able to create. The option value is passed to ulimit -c.
NoteThe
innodb_buffer_pool_in_core_file
variable can be used to reduce the size of core files on operating systems that support it. For more information, see Section 17.8.3.7, “Excluding or Including Buffer Pool Pages from Core Files”. -
Command-Line Format --datadir=dir_name
Type Directory name The path to the data directory.
-
--defaults-extra-file=
file_name
Command-Line Format --defaults-extra-file=file_name
Type File name Read this option file in addition to the usual option files. If the file does not exist or is otherwise inaccessible, the server exits with an error. If
file_name
is not an absolute path name, it is interpreted relative to the current directory. This must be the first option on the command line if it is used.For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.
-
Command-Line Format --defaults-file=file_name
Type File name Use only the given option file. If the file does not exist or is otherwise inaccessible, the server exits with an error. If
file_name
is not an absolute path name, it is interpreted relative to the current directory. This must be the first option on the command line if it is used.For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.
-
Command-Line Format --ledir=dir_name
Type Directory name If mysqld_safe cannot find the server, use this option to indicate the path name to the directory where the server is located.
This option is accepted only on the command line, not in option files. On platforms that use systemd, the value can be specified in the value of
MYSQLD_OPTS
. See Section 2.5.9, “Managing MySQL Server with systemd”. -
Command-Line Format --log-error=file_name
Type File name Write the error log to the given file. See Section 7.4.2, “The Error Log”.
-
Command-Line Format --mysqld-safe-log-timestamps=type
Type Enumeration Default Value utc
Valid Values system
hyphen
legacy
This option controls the format for timestamps in log output produced by mysqld_safe. The following list describes the permitted values. For any other value, mysqld_safe logs a warning and uses
UTC
format.-
UTC
,utc
ISO 8601 UTC format (same as
--log_timestamps=UTC
for the server). This is the default. -
SYSTEM
,system
ISO 8601 local time format (same as
--log_timestamps=SYSTEM
for the server). -
HYPHEN
,hyphen
YY-MM-DD h:mm:ss
format, as in mysqld_safe for MySQL 5.6. -
LEGACY
,legacy
YYMMDD hh:mm:ss
format, as in mysqld_safe prior to MySQL 5.6.
-
-
Command-Line Format --malloc-lib=[lib-name]
Type String The name of the library to use for memory allocation instead of the system
malloc()
library. The option value must be one of the directories/usr/lib
,/usr/lib64
,/usr/lib/i386-linux-gnu
, or/usr/lib/x86_64-linux-gnu
.The
--malloc-lib
option works by modifying theLD_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 usetcmalloc
. -
Prior to MySQL 8.0.21, if the option is given as
--malloc-lib=tcmalloc
, mysqld_safe looks for atcmalloc
library in/usr/lib
. Iftmalloc
is found, its path name is added to the beginning of theLD_PRELOAD
value for mysqld. Iftcmalloc
is not found, mysqld_safe aborts with an error.As of MySQL 8.0.21,
tcmalloc
is not a permitted value for the--malloc-lib
option. -
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.
NoteOn systems that manage the server using systemd, mysqld_safe is not available. Instead, specify the allocation library by setting
LD_PRELOAD
in/etc/sysconfig/mysql
.Linux users can use the
libtcmalloc_minimal.so
library on any platform for which atcmalloc
package is installed in/usr/lib
by adding these lines to themy.cnf
file:[mysqld_safe] malloc-lib=tcmalloc
To use a specific
tcmalloc
library, specify its full path name. Example:[mysqld_safe] malloc-lib=/opt/lib/libtcmalloc_minimal.so
-
-
Command-Line Format --mysqld=file_name
Type File name 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 accepted only on the command line, not in option files. On platforms that use systemd, the value can be specified in the value of
MYSQLD_OPTS
. See Section 2.5.9, “Managing MySQL Server with systemd”. -
Command-Line Format --mysqld-version=suffix
Type String This option is similar to the
--mysqld
option, but you specify only the suffix for the server program name. The base name is assumed to be mysqld. For example, if you use--mysqld-version=debug
, mysqld_safe starts the mysqld-debug program in theledir
directory. If the argument to--mysqld-version
is empty, mysqld_safe uses mysqld in theledir
directory.This option is accepted only on the command line, not in option files. On platforms that use systemd, the value can be specified in the value of
MYSQLD_OPTS
. See Section 2.5.9, “Managing MySQL Server with systemd”. -
Command-Line Format --nice=priority
Type Numeric Use the
nice
program to set the server's scheduling priority to the given value. -
Command-Line Format --no-defaults
Type String Do not read any option files. If program startup fails due to reading unknown options from an option file,
--no-defaults
can be used to prevent them from being read. This must be the first option on the command line if it is used.For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.
-
Command-Line Format --open-files-limit=count
Type String The number of files that mysqld should be able to open. The option value is passed to ulimit -n.
NoteYou must start mysqld_safe as
root
for this to function properly. -
Command-Line Format --pid-file=file_name
Type File name The path name that mysqld should use for its process ID file.
-
Command-Line Format --plugin-dir=dir_name
Type Directory name The path name of the plugin directory.
-
Command-Line Format --port=number
Type Numeric 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
operating system user. -
Command-Line Format --skip-kill-mysqld
Do not try to kill stray mysqld processes at startup. This option works only on Linux.
-
Command-Line Format --socket=file_name
Type File name The Unix socket file that the server should use when listening for local connections.
-
Command-Line Format --syslog
Deprecated Yes Command-Line Format --skip-syslog
Deprecated Yes --syslog
causes error messages to be sent tosyslog
on systems that support the logger program.--skip-syslog
suppresses the use ofsyslog
; messages are written to an error log file.When
syslog
is used for error logging, thedaemon.err
facility/severity is used for all log messages.Using these options to control mysqld logging is deprecated. To write error log output to the system log, use the instructions at Section 7.4.2.8, “Error Logging to the System Log”. To control the facility, use the server
log_syslog_facility
system variable. -
Command-Line Format --syslog-tag=tag
Deprecated Yes For logging to
syslog
, messages from mysqld_safe and mysqld are written with identifiers ofmysqld_safe
andmysqld
, respectively. To specify a suffix for the identifiers, use--syslog-tag=
, which modifies the identifiers to betag
mysqld_safe-
andtag
mysqld-
.tag
Using this option to control mysqld logging is deprecated. Use the server
log_syslog_tag
system variable instead. See Section 7.4.2.8, “Error Logging to the System Log”. -
Command-Line Format --timezone=timezone
Type String Set the
TZ
time zone environment variable to the given option value. Consult your operating system documentation for legal time zone specification formats. -
Command-Line Format --user={user_name|user_id}
Type String Type Numeric Run the mysqld server as the user having the name
user_name
or the numeric user IDuser_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 is not used. For example, this command does 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 forlibexec
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:
cd mysql_installation_directory
bin/mysqld_safe &
If mysqld_safe fails, even when invoked from the MySQL installation directory, specify the --ledir
and --datadir
options to indicate the directories in which the server and databases are located on your system.
mysqld_safe tries to use the sleep and date system utilities to determine how many times per second it has attempted to start. If these utilities are present and the attempted starts per second is greater than 5, mysqld_safe waits 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:
-
--log-error=
: Write error messages to the named error file.file_name
-
--syslog
: Write error messages tosyslog
on systems that support the logger program. -
--skip-syslog
: Do not write error messages tosyslog
. 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.
If none of these options is given, the default is --skip-syslog
.
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
.
Controlling mysqld logging from mysqld_safe is deprecated. Use the server's native syslog
support instead. For more information, see Section 7.4.2.8, “Error Logging to the System Log”.