I have an old Galera cluster (MySQL 5.5) that I am upgrading to Percona XtraDB (MySQL 5.7) on Ubuntu 18.04 LTS. I have successfully imported the database with xtrabackup and synced the cluster - so far so good.
My problem is that I can not stop the mysqld process on the first node, the one I started with
service mysql bootstrap-pxc with the normal
service mysql stop; I have to resort to
mysqladmin shutdown. The odd thing is that once I have restarted the first node with
service mysql start I can then sometimes stop it with
service mysql stop without problems and sometimes not. I have yet to find a pattern to this.
All other nodes in the cluster can be shut down with
service mysql stop without problems.