/etc/ is in percona-xtradb-cluster-server-5.6 5.6.21-25.8-0ubuntu3.
This file is owned by root:root, with mode 0o755.
..
/etc/mysql/
/etc/mysql/percona-xtradb-cluster.conf.d/
/etc/mysql/percona-xtradb-cluster.conf.d/client.cnf
/etc/mysql/percona-xtradb-cluster.conf.d/mysqld.cnf
/etc/mysql/percona-xtradb-cluster.conf.d/mysqld_safe.cnf
/etc/mysql/percona-xtradb-cluster.conf.d/isamchk.cnf
/etc/mysql/percona-xtradb-cluster.cnf
/etc/mysql/percona-xtradb-cluster/
/etc/mysql/percona-xtradb-cluster/debian-start
/etc/mysql/conf.d/
/etc/logcheck/
/etc/logcheck/ignore.d.paranoid/
/etc/logcheck/ignore.d.paranoid/percona-xtradb-cluster-server-5_6
/etc/logcheck/ignore.d.workstation/
/etc/logcheck/ignore.d.workstation/percona-xtradb-cluster-server-5_6
/etc/logcheck/ignore.d.server/
/etc/logcheck/ignore.d.server/percona-xtradb-cluster-server-5_6
/etc/init.d/
/etc/init.d/mysql
/etc/xinetd.d/
/etc/xinetd.d/mysqlchk