It's filed as MySQL bug#43398 (verified!) but it's triggered by cPanel doing evil.
Start a mysql server, as normalOf course you generally wouldn't run mysql_install_db while a server is running, but there's nothing to prevent you (or something else) from doing so!
Then run mysql_install_db (as root, like you would when you first install MySQL)
See a new binlog file get created, with ownership/group root!
--bootstrap just shouldn't initialise binlog, then there wouldn't be a issue.
cPanel runs mysql_install_db in its automatic upgrade scripts (dangerous already, automatically upgrading MySQL Server on a system!), it's run every night on cPanel systems even if no upgrade is done, and it behaves exactly as described above. It then chowns the binlog [Read more...]