xtrabackup fails with default Ubuntu permissions on /etc/my.sql

[trent--]

When using the xtrabackup-v2 SST method, with a default Ubuntu install including the following packages :

ii libmysqlclient18:amd64 5.5.47-0ubuntu0.14.04.1 amd64 MySQL database client library
ii mysql-common 5.5.47-0ubuntu0.14.04.1 all MySQL database common files, e.g. /etc/mysql/my.cnf
ii percona-toolkit 2.2.16-1 all Advanced MySQL and system command-line tools
ii percona-xtrabackup 2.3.3-1.trusty amd64 Open source backup tool for InnoDB and XtraDB
iU percona-xtradb-cluster-5.6-dbg 5.6.28-25.14-1.trusty amd64 Debugging package for Percona XtraDB Cluster
ii percona-xtradb-cluster-client-5.6 5.6.28-25.14-1.trusty amd64 Percona XtraDB Cluster database client binaries
ii percona-xtradb-cluster-common-5.6 5.6.28-25.14-1.trusty amd64 Percona XtraDB Cluster database common files (e.g. /etc/mysql/my.cnf)
ii percona-xtradb-cluster-galera-3.x 3.14-1.trusty amd64 Galera components of Percona XtraDB Cluster
iF percona-xtradb-cluster-server-5.6 5.6.28-25.14-1.trusty amd64 Percona XtraDB Cluster database server binaries

SST fails with this error on the target server, in file /var/lib/mysql/.sst/innobackup.move.log :

Could not open required defaults file: /etc/my.cnf
Fatal error in defaults handling. Program aborted

A workaround is to give read permission to mysql user for this file :
chown root:mysql /etc/mysql/debian.cnf ; chmod 640 /etc/mysql/debian.cnf

[Sergei Glushchenko (sergei.glushchenko)]

I am not sure it's an xtrabackup bug. Xtrabackup is used as an tool here. PXC invokes it providing config as an argument. It's under PXC control which user xtrabackup runs under. /etc/my.cnf is also a part of PXC package I believe, not an xtrbackup one.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PXC-1889