The Error Log 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. 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: 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. 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: 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: •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  --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 . • 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. 1029 Default Error Log Destination on Unix and Unix-Like Systems Note How the Default Error Log Destination Affects Log Sinks