rsync: failed to set permissions on "."

$ sudo dpkg -l | grep -i "percona"
[sudo] password for svadmin:
ii percona-xtrabackup 2.2.10-1.trusty amd64 Open source backup tool for InnoDB and XtraDB
ii percona-xtradb-cluster-56 5.6.22-25.8-978.trusty amd64 Percona XtraDB Cluster with Galera
ii percona-xtradb-cluster-client-5.6 5.6.22-25.8-978.trusty amd64 Percona XtraDB Cluster database client binaries
ii percona-xtradb-cluster-common-5.6 5.6.22-25.8-978.trusty amd64 Percona XtraDB Cluster database common files (e.g. /etc/mysql/my.cnf)
ii percona-xtradb-cluster-galera-3 3.9.3494.trusty amd64 Metapackage for latest version of galera3.
ii percona-xtradb-cluster-galera-3.x 3.9.3494.trusty amd64 Galera components of Percona XtraDB Cluster
ii percona-xtradb-cluster-server-5.6 5.6.22-25.8-978.trusty amd64 Percona XtraDB Cluster database server binaries

why would rsync failed?

rsync: failed to set permissions on "." (in rsync_sst): Operation not permitted (1)
rsync: recv_generator: mkdir "FedTest" (in rsync_sst) failed: Permission denied (13)
*** Skipping any contents from this failed directory ***
rsync: open "ibdata1" (in rsync_sst) failed: Permission denied (13)
2015-05-20 11:45:12 13218 [Note] WSREP: (6b694432, 'tcp://0.0.0.0:4567') turning message relay requesting off
rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1183) [sender=3.1.0]
WSREP_SST: [ERROR] rsync returned code 23: (20150520 11:45:12.039)
2015-05-20 11:45:12 13218 [ERROR] WSREP: Failed to read from: wsrep_sst_rsync --role 'donor' --address '10.1.1.101:4444/rsync_sst' --auth '(null)' --socket '/var/run/mysqld/mysqld.sock' --datadir '/var/lib/mysql/' --defaults-file '/etc/mysql/my.cnf' '' --gtid '19bf9b09-ed47-11e4-8005-f75eee435bfc:930436'
2015-05-20 11:45:12 13218 [ERROR] WSREP: Process completed with error: wsrep_sst_rsync --role 'donor' --address '10.1.1.101:4444/rsync_sst' --auth '(null)' --socket '/var/run/mysqld/mysqld.sock' --datadir '/var/lib/mysql/' --defaults-file '/etc/mysql/my.cnf' '' --gtid '19bf9b09-ed47-11e4-8005-f75eee435bfc:930436': 255 (Unknown error 255)

db2:~$ grep sst_method /etc/mysql/my.cnf
wsrep_sst_method=rsync

db2:~$ sudo ls -l /var/lib/mysql
lrwxrwxrwx 1 root root 12 Mei 19 12:36 /var/lib/mysql -> /mnt/db/db2/

db2:~$ sudo ls -l /var/lib/mysql/
total 2330648
-rw-rw---- 1 mysql mysql 56 Mei 20 11:09 auto.cnf
-rw------- 1 mysql mysql 134219048 Mei 20 11:44 galera.cache
-rw-rw---- 1 mysql mysql 104 Mei 20 11:44 grastate.dat
-rw-rw---- 1 mysql mysql 104857600 Mei 20 11:44 ibdata1
-rw-rw---- 1 mysql mysql 1073741824 Mei 20 11:44 ib_logfile0
-rw-rw---- 1 mysql mysql 1073741824 Mei 20 11:09 ib_logfile1

/etc/mysql/my.cnf

[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysqld_safe]
socket = /var/run/mysqld/mysqld.sock
nice = 0
[mysqld]
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /var/lib/mysql
tmpdir = /tmp
lc-messages-dir = /usr/share/mysql
federated
skip-external-locking
bind-address = 10.1.1.101
key_buffer = 24M
tmp_table_size = 64M
max_heap_table_size = 64M
max_allowed_packet = 512M
skip_name_resolve
memlock
sysdate_is_now=1
thread_cache_size = 512
query_cache_size = 0
table_open_cache=1024
lower_case_table_names=0
explicit_defaults_for_timestamp=1
log_error = /var/log/mysql.log
binlog_format=ROW
innodb_buffer_pool_size=94065M
innodb_flush_log_at_trx_commit=2
innodb_file_per_table=1
innodb_data_file_path = ibdata1:100M:autoextend
innodb_read_io_threads=4
innodb_write_io_threads=4
innodb_io_capacity=200
innodb_doublewrite=1
innodb_log_file_size=1024M
innodb_log_buffer_size=96M
innodb_buffer_pool_instances=8
innodb_log_files_in_group=2
innodb_thread_concurrency=64
innodb_flush_method = O_DIRECT
innodb_autoinc_lock_mode=2
innodb_stats_on_metadata=0
default_storage_engine=innodb
wsrep_provider=/usr/lib/libgalera_smm.so
wsrep_cluster_name = dbcluster
wsrep_sst_method=rsync
wsrep_node_name = db2
wsrep_cluster_address=gcomm://10.1.1.101:4567,10.1.1.101:4567
expire_logs_days = 10
max_binlog_size = 100M
[mysqldump]
quick
quote-names
max_allowed_packet = 16M
[mysql]
[isamchk]
key_buffer = 16M
!includedir /etc/mysql/conf.d/

I also found below message in syslog

rsync: ERROR: cannot stat destination “.” (in rsync_sst): Permission denied