I've installed the WP-DBManager plugin. It appears to be correctly configured. Selecting the "Backup DB" menu option shows a bunch of green messages showing configuration options are acceptable. But when I run the backup, either manually or scheduled, the content of the .sql file is the usage message for mysqldump:
/usr/bin/mysqldump Ver 8.23 Distrib 3.23.58, for redhat-linux-gnu (i386)
By Igor Romanenko, Monty, Jani & Sinisa
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL license
Dumping definition and data mysql database or table
Usage: /usr/bin/mysqldump [OPTIONS] database [tables]
OR /usr/bin/mysqldump [OPTIONS] --databases [OPTIONS] DB1 [DB2 DB3...]
OR /usr/bin/mysqldump [OPTIONS] --all-databases [OPTIONS]
...etc...
And that message is all that's in the file. What am I missing?