1. setup MariaDB cluster with galera 4, and the cluster works
2. failed to execute mariabackup as flow

[root@node1 ~]# mariabackup
mariabackup: automatic setup request is unsupported by option '--open_files_limit'
[root@node1 ~]# mariabackup --help
mariabackup: automatic setup request is unsupported by option '--open_files_limit'
[root@node1 ~]# mariabackup --target-dir=/opt --user=root --password=mypassword
mariabackup: automatic setup request is unsupported by option '--open_files_limit'

[root@node1 ~]# rpm -qa|grep MariaDB
MariaDB-server-10.5.6-1.el7.centos.x86_64
MariaDB-compat-10.5.6-1.el7.centos.x86_64
MariaDB-backup-10.5.6-1.el7.centos.x86_64
MariaDB-common-10.5.6-1.el7.centos.x86_64
MariaDB-client-10.5.6-1.el7.centos.x86_64

[root@node1 ~]# cd /etc/my.cnf.d/
[root@node1 my.cnf.d]# ls
enable_encryption.preset mysql-clients.cnf server.cnf spider.cnf z-abc.cnf
[root@node1 my.cnf.d]# cat z-abc.cnf

[mariadb]

default-storage-engine=INNODB

default-time-zone='+8:00'

skip-name-resolve

wait_timeout=20

max_connections=5000

# determine a good value for open_files_limit automatically

autoset_open_files_limit

max_allowed_packet=1G

# Server Configuration

log_error                = mariadbd.err

innodb_buffer_pool_size  = 1G

innodb_log_file_size=64M

innodb_flush_method=O_DIRECT

innodb_file_per_table           = 1

# Cluster Configuration

wsrep_provider           = /usr/lib64/galera-4/libgalera_smm.so

wsrep_cluster_address="gcomm://192.168.11.178,192.168.11.179,192.168.11.201"

wsrep_cluster_name       = abcCluster

wsrep_on                 = ON

binlog_format            = ROW

innodb_autoinc_lock_mode = 2

wsrep_node_address = 192.168.11.178

wsrep_sst_method=rsync

[mariabackup]

open_files_limit=65535

[root@node1 my.cnf.d]#