mysqld_safe

mysqld_safe è il modo consigliato per avviare un server mysqld su Unix e NetWare. mysqld_safe aggiunge alcune caratteristiche di sicurezza, come il riavvio del server nel caso in cui avvenga un errore e il logging a runtime in un file di log degli errori. Le descrizioni degli errori registrati nel log e i comportamenti specifici di NetWare sono presenti più avanti in questa sezione.

mysqld_safe tenta di avviare un eseguibile chiamato mysqld. Per modificare questo comportamento predefinito e specificare esplicitamente il nome del server da lanciare, si passi l'opzione --mysqld o --mysqld-version a mysqld_safe. Si può anche usare --ledir per indicare la directory nella quale mysqld_safe dovrà cercare il server server.

Molte delle opzioni di mysqld_safe sono identiche a quelle di mysqld.

Le opzioni sconosciute a mysqld_safe, se sono specificate da riga di comando vengono passate a mysqld, ma se sono specificate nel gruppo [mysqld_safe] di un file di configurazione vengono ignorate.

mysqld_safe legge tutte le opzioni dalle sezioni [mysqld], [server] e [mysqld_safe] dei file delle opzioni. Per esempio, se si specifica una sezione [mysqld] come la seguente, mysqld_safe è in grado di trovare e usare l'opzione --log-error:

[mysqld]
log-error=error.log

Per compatibilità all'indietro, mysqld_safe legge anche le sezioni [safe_mysqld], però è meglio rinominare tali sezioni di [mysqld_safe] in MySQL 5.1.

mysqld_safe Options

mysqld_safe supporta le seguenti opzioni:

• --help
  
  • Mostra un messaggio di help e termina.
• --autoclose
  
  • (solo su NetWare) Su NetWare, mysqld_safe fornisce una presenza su schermo. Quando mysqld_safe NLM libera la memoria e si arresta, lo schermo non va via per default. Invece chiede un input all'utente:

*<NLM has terminated; Press any key to close the screen>*

Se si desidera che NetWare chiuda lo schermo automaticamente, si può usare l'opzione --autoclose di mysqld_safe.

• --basedir=percorso
  
  • Il percorso della directory di installazione di MariaDB.
• --core-file-size=dimensioni
  
  • Le dimensioni del file principale che mysqld deve poter creare. Il valore di questa opzione viene passato a ulimit -c.
• --datadir=path
  
  • The path to the data directory.
• --defaults-extra-file=path
  
  • 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.
• --defaults-file=file_name
  
  • 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.
• --ledir=path
  
  • If mysqld_safe cannot find the server, use this option to indicate the path name to the directory where the server is located.
• --log-error=file_name
  
  • Write the error log to the given file.
• --mysqld=prog_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.
• --mysqld-version=suffix
  
  • 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.
• --nice=priority
  
  • Use the nice program to set the server´s scheduling priority to the given value.
• --no-defaults
  
  • Do not read any option files. This must be the first option on the command line if it is used.
• --open-files-limit=count
  
  • 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!
• --pid-file=file_name
  
  • The path name of the process ID file.
• --port=port_num
  
  • 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.
• --skip-kill-mysqld
  
  • Do not try to kill stray mysqld processes at startup. This option works only on Linux.
• --socket=path
  
  • The Unix socket file that the server should use when listening for local connections.
• --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. These options were added in MySQL 5.1.20.
• --syslog-tag=tag
  
  • 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=tag, which modifies the tags to be mysqld_safe-tag and mysqld-tag. This option was added in MySQL 5.1.21.
• --timezone=timezone
  
  • Set the TZ time zone environment variable to the given option value. Consult your operating system documentation for legal time zone specification formats.
• --user={user_name|user_id}
  
  • 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 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.

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.

As of MySQL 5.1.20, 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 (host_name.err in the data directory), or to a named file if the --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.

Before MySQL 5.1.20, error logging is controlled only with the --log-error option. If it is given, messages go to the named error file. Otherwise, messages go to the default error file.

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.

On NetWare, mysqld_safe is a NetWare Loadable Module (NLM) that is ported from the original Unix shell script. It starts the server as follows:

1. Runs a number of system and option checks.
2. Runs a check on MyISAM tables.
3. Provides a screen presence for the MySQL server.
4. Starts mysqld, monitors it, and restarts it if it terminates in error.
5. Sends error messages from mysqld to the host_name.err file in the data directory.
6. Sends mysqld_safe screen output to the host_name.safe file in the data directory.