mmmm then I uninstalled everything for 5.6: apt-get remove --purge percona***** - and tried installing 5.5. The same two systems gave problems again - could not set the root password: Unable to set password for the Percona Server "root" user │ │ │ │ An error occurred while setting the password for the Percona Server administrative user. This may have happened because the account already has a password, or because of a communication problem with the Percona Server │ │ daemon. The third system worked fine. again. This is from the working server: -------------------------------------------------------------------------------------------------------------------------------------------------------- Get:1 http://repo.percona.com/apt/ precise/main percona-xtrabackup amd64 2.1.6-702-1.precise [8 499 kB] Get:2 http://repo.percona.com/apt/ precise/main percona-xtradb-cluster-common-5.5 all 5.5.34-25.9-607.precise [2 832 B] Get:3 http://repo.percona.com/apt/ precise/main percona-xtradb-cluster-client-5.5 amd64 5.5.34-25.9-607.precise [8 512 kB] Get:4 http://repo.percona.com/apt/ precise/main percona-xtradb-cluster-galera-2.x amd64 163.precise [1 512 kB] Get:5 http://repo.percona.com/apt/ precise/main percona-xtradb-cluster-server-5.5 amd64 5.5.34-25.9-607.precise [18,0 MB] Fetched 36,5 MB in 10s (3 393 kB/s) Preconfiguring packages ... Selecting previously unselected package percona-xtrabackup. (Reading database ... 76470 files and directories currently installed.) Unpacking percona-xtrabackup (from .../percona-xtrabackup_2.1.6-702-1.precise_amd64.deb) ... Selecting previously unselected package percona-xtradb-cluster-common-5.5. Unpacking percona-xtradb-cluster-common-5.5 (from .../percona-xtradb-cluster-common-5.5_5.5.34-25.9-607.precise_all.deb) ... Selecting previously unselected package percona-xtradb-cluster-client-5.5. Unpacking percona-xtradb-cluster-client-5.5 (from .../percona-xtradb-cluster-client-5.5_5.5.34-25.9-607.precise_amd64.deb) ... Selecting previously unselected package percona-xtradb-cluster-galera-2.x. Unpacking percona-xtradb-cluster-galera-2.x (from .../percona-xtradb-cluster-galera-2.x_163.precise_amd64.deb) ... Selecting previously unselected package percona-xtradb-cluster-server-5.5. Unpacking percona-xtradb-cluster-server-5.5 (from .../percona-xtradb-cluster-server-5.5_5.5.34-25.9-607.precise_amd64.deb) ... Processing triggers for man-db ... Processing triggers for ureadahead ... Setting up percona-xtrabackup (2.1.6-702-1.precise) ... Setting up percona-xtradb-cluster-common-5.5 (5.5.34-25.9-607.precise) ... Setting up percona-xtradb-cluster-client-5.5 (5.5.34-25.9-607.precise) ... Setting up percona-xtradb-cluster-galera-2.x (163.precise) ... Setting up percona-xtradb-cluster-server-5.5 (5.5.34-25.9-607.precise) ... * Stopping MySQL (Percona XtraDB Cluster) mysqld [ OK ] 140122 16:10:49 [Note] WSREP: Read nil XID from storage engines, skipping position init 140122 16:10:49 [Note] WSREP: wsrep_load(): loading provider library 'none' 140122 16:10:49 [Note] Plugin 'FEDERATED' is disabled. 140122 16:10:49 InnoDB: The InnoDB memory heap is disabled 140122 16:10:49 InnoDB: Mutexes and rw_locks use GCC atomic builtins 140122 16:10:49 InnoDB: Compressed tables use zlib 1.2.3 140122 16:10:49 InnoDB: Using Linux native AIO 140122 16:10:49 InnoDB: Initializing buffer pool, size = 128.0M 140122 16:10:49 InnoDB: Completed initialization of buffer pool 140122 16:10:49 InnoDB: highest supported file format is Barracuda. 140122 16:10:49 InnoDB: Waiting for the background threads to start 140122 16:10:50 Percona XtraDB (http://www.percona.com) 5.5.34-rel32.0 started; log sequence number 1597945 140122 16:10:50 [Note] WSREP: Service disconnected. 140122 16:10:51 [Note] WSREP: Some threads may fail to exit. 140122 16:10:51 InnoDB: Starting shutdown... 140122 16:10:54 InnoDB: Shutdown completed; log sequence number 1597945 * Percona XtraDB Cluster is distributed with several useful UDF (User Defined Function) from Percona Toolkit. * Run the following commands to create these functions: mysql -e "CREATE FUNCTION fnv1a_64 RETURNS INTEGER SONAME 'libfnv1a_udf.so'" mysql -e "CREATE FUNCTION fnv_64 RETURNS INTEGER SONAME 'libfnv_udf.so'" mysql -e "CREATE FUNCTION murmur_hash RETURNS INTEGER SONAME 'libmurmur_udf.so'" * See http://www.percona.com/doc/percona-server/5.5/management/udf_percona_toolkit.html for more details * Starting MySQL (Percona XtraDB Cluster) database server mysqld [ OK ] Processing triggers for libc-bin ... ldconfig deferred processing now taking place ----------------------------------------------------------------------------------------------------------------------------- and this is from the nonworking server: ----------------------------------------------------------------------------------------------------------------------------- Get:1 http://repo.percona.com/apt/ precise/main percona-xtrabackup amd64 2.1.6-702-1.precise [8 499 kB] Get:2 http://repo.percona.com/apt/ precise/main percona-xtradb-cluster-common-5.5 all 5.5.34-25.9-607.precise [2 832 B] Get:3 http://repo.percona.com/apt/ precise/main percona-xtradb-cluster-client-5.5 amd64 5.5.34-25.9-607.precise [8 512 kB] Get:4 http://repo.percona.com/apt/ precise/main percona-xtradb-cluster-galera-2.x amd64 163.precise [1 512 kB] Get:5 http://repo.percona.com/apt/ precise/main percona-xtradb-cluster-server-5.5 amd64 5.5.34-25.9-607.precise [18,0 MB] Fetched 36,5 MB in 10s (3 534 kB/s) Preconfiguring packages ... (Reading database ... 76523 files and directories currently installed.) Removing mysql-client-core-5.5 ... Removing mysql-server-core-5.5 ... Processing triggers for man-db ... Selecting previously unselected package percona-xtrabackup. (Reading database ... 76489 files and directories currently installed.) Unpacking percona-xtrabackup (from .../percona-xtrabackup_2.1.6-702-1.precise_amd64.deb) ... Selecting previously unselected package percona-xtradb-cluster-common-5.5. Unpacking percona-xtradb-cluster-common-5.5 (from .../percona-xtradb-cluster-common-5.5_5.5.34-25.9-607.precise_all.deb) ... Selecting previously unselected package percona-xtradb-cluster-client-5.5. Unpacking percona-xtradb-cluster-client-5.5 (from .../percona-xtradb-cluster-client-5.5_5.5.34-25.9-607.precise_amd64.deb) ... Selecting previously unselected package percona-xtradb-cluster-galera-2.x. Unpacking percona-xtradb-cluster-galera-2.x (from .../percona-xtradb-cluster-galera-2.x_163.precise_amd64.deb) ... Selecting previously unselected package percona-xtradb-cluster-server-5.5. Unpacking percona-xtradb-cluster-server-5.5 (from .../percona-xtradb-cluster-server-5.5_5.5.34-25.9-607.precise_amd64.deb) ... Processing triggers for man-db ... Processing triggers for ureadahead ... Setting up percona-xtrabackup (2.1.6-702-1.precise) ... Setting up percona-xtradb-cluster-common-5.5 (5.5.34-25.9-607.precise) ... Setting up percona-xtradb-cluster-client-5.5 (5.5.34-25.9-607.precise) ... Setting up percona-xtradb-cluster-galera-2.x (163.precise) ... Setting up percona-xtradb-cluster-server-5.5 (5.5.34-25.9-607.precise) ... * Stopping MySQL (Percona XtraDB Cluster) mysqld [ OK ] 140122 16:10:50 [ERROR] WSREP: Query cache is not supported (size=16777216 type=0) 140122 16:10:50 [ERROR] Aborting * Percona XtraDB Cluster is distributed with several useful UDF (User Defined Function) from Percona Toolkit. * Run the following commands to create these functions: mysql -e "CREATE FUNCTION fnv1a_64 RETURNS INTEGER SONAME 'libfnv1a_udf.so'" mysql -e "CREATE FUNCTION fnv_64 RETURNS INTEGER SONAME 'libfnv_udf.so'" mysql -e "CREATE FUNCTION murmur_hash RETURNS INTEGER SONAME 'libmurmur_udf.so'" * See http://www.percona.com/doc/percona-server/5.5/management/udf_percona_toolkit.html for more details * Starting MySQL (Percona XtraDB Cluster) database server mysqld * The server quit without updating PID file (/var/run/mysqld/mysqld.pid). [fail] invoke-rc.d: initscript mysql, action "start" failed. Processing triggers for libc-bin ... ldconfig deferred processing now taking place