MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
On Unix and Unix-like systems, mysqld uses
the --log-error option to
determine whether mysqld writes the error log
to the console or a file, and, if to a file, the file name:
If --log-error is not given,
mysqld writes the error log to the
console.
If --log-error is given
without naming a file, mysqld writes the
error log to a file named
host_name.err
If --log-error is given to
name a file, mysqld writes the error log
to 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.
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
If the server writes the error log to the console, it sets the
log_error system variable to
stderr. Otherwise, the server writes the
error log to a file and sets
log_error to the file name.