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•If --log-error  is not given, or is given without naming a file, the default destination is a file named host_name .err  in the data directory, unless the --pid-file  option is specified. In that case, the file name is the PID file base name with a suffix of .err  in the data directory. 

•If --log-error  is given to name a file, the default destination is that file (with an .err  suffix added if the name has no suffix). The file location is under the data directory unless an absolute path name is given to specify a different location. 

If the default error log destination is the console, the server sets the log_error  system variable to stderr . Otherwise, the default destination is a file and the server sets log_error  to the file name. 

## Default Error Log Destination on Unix and Unix-Like Systems 

On Unix and Unix-like systems, mysqld  uses the --log-error  option to determine whether the default error log destination is the console or a file, and, if a file, the file name: 

•If --log-error  is not given, the default destination is the console. 

•If --log-error  is given without naming a file, the default destination is a file named host_name .err in the data directory. 

•If --log-error  is given to name a file, the default destination is that file (with an .err  suffix added if the name has no suffix). The file location is under the data directory unless an absolute path name is given to specify a different location. 

•If --log-error  is given in an option file in a [mysqld] , [server] , or [mysqld_safe]  section, on systems that use mysqld_safe  to start the server, mysqld_safe  finds and uses the option, and passes it to mysqld . 

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## Note 

It is common for Yum or APT package installations to configure an error log file location under /var/log  with an option like log-error=/var/log/ mysqld.log  in a server configuration file. Removing the path name from the option causes the host_name .err  file in the data directory to be used. 

If the default error log destination is the console, the server sets the log_error  system variable to stderr . Otherwise, the default destination is a file and the server sets log_error  to the file name. 

## How the Default Error Log Destination Affects Log Sinks 

After the server interprets the error log destination configuration options, it sets the log_error  system variable to indicate the default error log destination. Log sink components may base their own output destination on the log_error  value, or determine their destination independently of log_error 

If log_error  is stderr , the default error log destination is the console, and log sinks that base their output destination on the default destination also write to the console: 

• log_sink_internal , log_sink_json , log_sink_test : These sinks write to the console. This is true even for sinks such as log_sink_json  that can be enabled multiple times; all instances write to the console. 

• log_sink_syseventlog : This sink writes to the system log, regardless of the log_error  value. 

If log_error  is not stderr , the default error log destination is a file and log_error  indicates the file name. Log sinks that base their output destination on the default destination base output file naming on that file name. (A sink might use exactly that name, or it might use some variant thereof.) Suppose that the log_error  value file_name . Then log sinks use the name like this: 

