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 5.1.4, "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 4.2.6, "Using Option
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
For backward compatibility, mysqld_safe also reads [safe_mysqld]
sections, but to be current you should rename such sections to
mysqld_safe supports the following options. It also reads option files
and supports the options for processing them described at
Section 4.2.7, "Command-Line Options that Affect Option-File Handling".
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 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
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 5.5.54, this option is accepted only on the command
line, not in option files.
Write the error log to the given file. See Section 5.4.2, "The
o --malloc-lib=[lib_name] The name of the library to use for memory
allocation instead of the system malloc() library. As of MySQL
5.5.52, 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 5.5.52, 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. It is possible that the shortcut form will
not work under certain configurations, in which case you should
specify a path name instead.
As of MySQL 5.5.50, MySQL distributions no longer include a
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:
o 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.
o 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.
o If the option is given as --malloc-lib=/path/to/some/library,
that full path is added to the beginning of the LD_PRELOAD
value. If the full path points to a nonexistent or unreadable
file, mysqld_safe aborts with an error.
o 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.
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 5.5.52, this option can be given only on the command
line and not in an option file.
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 5.5.52, this option can be given only on the command
line and not in an option file.
Use the nice program to set the server's scheduling priority to the
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.
You must start mysqld_safe as root for this to function
The path name that mysqld should use for its process ID file.
The path name of the plugin directory. This option was added in
The Unix socket file that the server should use when listening for
o --syslog, --skip-syslog
--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 facility/severity is
used for all log messages.
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=tag,
which modifies the identifiers to be mysqld_safe-tag and
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 2.1.4,
"Installation Layouts".) mysqld_safe expects one of the following
conditions to be true:
o 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
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
shell> cd mysql_installation_directory
shell> 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
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
There are several mysqld_safe options for controlling the destination
of these messages:
o --log-error=file_name: Write error messages to the named error
o --syslog: Write error messages to syslog on systems that support
the logger program.
o --skip-syslog: Do not write error messages to syslog. Messages are
written to the default error log file (host_name.err in the data
directory), or to a named file if the --log-error option is given.
If none of these options is given, the default is --skip-syslog.
If --log-error and --syslog 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.
General Public License for more details.
You should have received a copy of the GNU General Public License along
with the program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see
For more information, please refer to the MySQL Reference Manual, which
may already be installed locally and which is also available online at
Oracle Corporation (http://dev.mysql.com/).
MySQL 5.5 11/26/2016 MYSQLD_SAFE(1)
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