MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
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 2.5.10, “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 5.1.6, “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 4.2.2.2, “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 4.2.2.2, “Using Option Files”.
Table 4.6 mysqld_safe Options
| Option Name | Description | Introduced | Deprecated |
|---|---|---|---|
| --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 | 5.7.11 | |
| --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 | Yes | |
| --socket | Socket file on which to listen for Unix socket connections | ||
| --syslog | Write error messages to syslog | Yes | |
| --syslog-tag | Tag suffix for messages written to syslog | Yes | |
| --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 |
|---|
| Command-Line Format | --help |
|---|
Display a help message and exit.
| Command-Line Format | --basedir=dir_name |
|---|---|
| Type | Directory name |
| 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 |
| 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.
| Command-Line Format | --datadir=dir_name |
|---|---|
| Type | Directory name |
| 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 |
| 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 4.2.2.3, “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 4.2.2.3, “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.
As of MySQL 5.7.17, 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 2.5.10, “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 5.4.2, “The Error Log”.
| Command-Line Format | --mysqld-safe-log-timestamps=type |
|---|---|
| Introduced | 5.7.11 |
| Type | Enumeration |
| Default Value | utc |
| Valid Values |
|
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.
This option was added in MySQL 5.7.11.
| 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. As of
MySQL 5.7.15, 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. Prior to
MySQL 5.7.15, 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
5.7. It is possible for the shortcut form not
to work under certain configurations, in which case you
should specify a path name instead.
As of MySQL 5.7.13, MySQL distributions no longer include
a tcmalloc library.
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.
Prior to MySQL 5.7.31, 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.
As of MySQL 5.7.31, 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/libraryLD_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.
On 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 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
| 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.
As of MySQL 5.7.15, 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 2.5.10, “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 the
ledir directory. If the argument to
--mysqld-version is
empty, mysqld_safe uses
mysqld in the ledir
directory.
As of MySQL 5.7.15, 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 2.5.10, “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 4.2.2.3, “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.
You 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.
From MySQL 5.7.2 to 5.7.17, mysqld_safe
has its own process ID file, which is always named
mysqld_safe.pid and located in the
MySQL data directory.
| 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 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 for error logging,
the daemon.err facility/severity is used
for all log messages.
Using these options to control mysqld
logging is deprecated as of MySQL 5.7.5. Use the server
log_syslog system variable
instead. To control the facility, use the server
log_syslog_facility system
variable. See Section 5.4.2.3, “Error Logging to the System Log”.
| Command-Line Format | --syslog-tag=tag |
|---|---|
| Deprecated | Yes |
For logging to syslog, messages from
mysqld_safe and mysqld
are written with identifiers of
mysqld_safe and
mysqld, respectively. To specify a suffix
for the identifiers, use
--syslog-tag=,
which modifies the identifiers to be
tagmysqld_safe-
and
tagmysqld-.
tag
Using this option to control mysqld
logging is deprecated as of MySQL 5.7.5. Use the server
log_syslog_tag system
variable instead. See Section 5.4.2.3, “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 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 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 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:
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 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
(host_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 as of MySQL
5.7.5. Use the server's native syslog
support instead. For more information, see
Section 5.4.2.3, “Error Logging to the System Log”.