问题
centos直接安装mariadb会遇到众多问题。如果直接安装MysqL,由于oracle官方维护不够给力，使用起来有一定的风险，所以必须要安装mariadb。如果用yum安装（在阿里云亲测），由于网络不好，下载安装包的过程中，总是容易中断。如果用源码安装，先要求装gnutls,gnutls又依赖nettle，但是nettle即使版本是按gnutls要求安装的，仍然会报：Libnettle 3.1 was not found. 的问题
规划:
日志路径：/home/datum/data/logs/mariadb
数据库表数据路径： /home/datum/data/appdata/maria_data/dbdata
sock路径： /home/datum/data/appdata/maria_data/sock/
给相关的所有文件夹递归的赋权限：chmod -R 777/home/datum/data
下载安装文件：
先进入 https://mirrors.tuna.tsinghua.edu.cn/mariadb/mariadb-10.2.6/yum/centos6-amd64/rpms/ 选择要安装的具体文件
再用命令下载安装文件：
wget https://mirrors.tuna.tsinghua.edu.cn/mariadb/mariadb-10.2.6/yum/centos6-amd64/rpms/MariaDB-10.2.6-centos6-x86_64-client.rpm
wget https://mirrors.tuna.tsinghua.edu.cn/mariadb/mariadb-10.2.6/yum/centos6-amd64/rpms/MariaDB-10.2.6-centos6-x86_64-server.rpm
如果下载失败，进入官方库下载： http://yum.mariadb.org/10.2/centos6-amd64/rpms/
wgethttp://yum.mariadb.org/10.2/centos6-amd64/rpms/MariaDB-10.2.9-centos6-x86_64-common.rpm
wget http://yum.mariadb.org/10.2/centos6-amd64/rpms/MariaDB-10.2.9-centos6-x86_64-compat.rpm
wget http://yum.mariadb.org/10.2/centos6-amd64/rpms/MariaDB-10.2.9-centos6-x86_64-client.rpm
wgethttp://yum.mariadb.org/10.2/centos6-amd64/rpms/MariaDB-10.2.9-centos6-x86_64-server.rpm
安装：
卸载老版，以免产生冲突：卸载老版，以免产生冲突 ： yum remove MysqL-libs
安装所依赖的基础库：yum -y install galera perl perl-DBI
安装commn,compat,命令：rpm -ivh MariaDB-10.2.9-centos6-x86_64-common.rpm MariaDB-10.2.9-centos6-x86_64-compat.rpm
安装客户端：rpm -ivh MariaDB-10.2.9-centos6-x86_64-client.rpm
再安装server,命令： rpm -ivh MariaDB-10.2.6-centos6-x86_64-server.rpm注意： commn,compat要一起安装，否则会报以下的错误：
#rpm -ivh MariaDB-10.2.9-centos6-x86_64-compat.rpm
warning: MariaDB-10.2.9-centos6-x86_64-compat.rpm: Header V4 DSA/SHA1 Signature,key ID 1bb943db: NOKEY
error: Failed dependencies:
MariaDB-common is needed by MariaDB-compat-10.2.9-1.el6.x86_64
# rpm -ivh MariaDB-10.2.9-centos6-x86_64-common.rpm
warning: MariaDB-10.2.9-centos6-x86_64-common.rpm: Header V4 DSA/SHA1 Signature,key ID 1bb943db: NOKEY
error: Failed dependencies:
MariaDB-compat is needed by MariaDB-common-10.2.9-1.el6.x86_64
数据库配置：
配置数据库。先看有没有文件/etc/my.cnf ，如果没有，执行cp /usr/share/MysqL/my-large.cnf /etc/my.cnf
先将配置文件拷到默认位置，然后再修改里面的内容。
配置内容：
# The following options will be passed to all MariaDB clients
[client]
#password = your_password
port = 3306
socket=/home/datum/data/appdata/maria_data/sock/MysqL.sock
# Here follows entries for some specific programs
# The MariaDB server
[MysqLd]
port = 3306
datadir=/home/datum/data/appdata/maria_data/dbdata
socket=/home/datum/data/appdata/maria_data/sock/MysqL.sock
skip-external-locking
key_buffer_size = 256M
max_allowed_packet = 1M
table_open_cache = 256
sort_buffer_size = 1M
read_buffer_size = 1M
read_rnd_buffer_size = 4M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size= 16M
# Try number of cpu's*2 for thread_concurrency
thread_concurrency = 8
# Replication Master Server (default)
# binary logging is required for replication
log-bin=MysqL-bin
# binary logging format - mixed recommended
binlog_format=mixed
# required unique id between 1 and 2^32 - 1
# defaults to 1 if master-host is not set
# but will not function as a master if omitted
server-id = 1
log-error=/home/datum/data/logs/mariadb/MysqL.log
slow-query-log = 1
slow-query-log-file =/home/datum/data/logs/mariadb/MysqL-slow.log
long_query_time =5
wait_timeout=90000
interactive_timeout=90000
#10s per transaction
innodb_lock_wait_timeout=10
#MysqL 事件计划开启
event_scheduler=1
#与cpu相关=cpu*2
thread_concurrency=20
# from net http://www.tuicool.com/articles/a6jeiu http://www.jb51.net/article/58537.htm
# 启用 InnoDB 的每张表一个数据文件设置
innodb_file_per_table=1
# 配置 MysqL 的线程缓存数量
thread_cache_size =32
# 配置 MysqL 的查询缓存容量。验证： show status like '%Qcache%';
query_cache_type=1
# query_cache_limit = 256K
# query_cache_min_res_unit = 2k
query_cache_size=128M
[MysqLdump]
quick
max_allowed_packet = 16M
[MysqL]
no-auto-rehash
# Remove the next comment character if you are not familiar with sql
#safe-updates
[myisamchk]
key_buffer_size = 128M
sort_buffer_size = 128M
read_buffer = 2M
write_buffer = 2M
[MysqLhotcopy]
interactive-timeout
设置相关文件夹的权限： chown -R MysqL:MysqL /home/datum/data/logs/mariadb
chown -R MysqL:MysqL /home/datum/data/appdata/maria_data
chmod -R 777 /home/datum/data/appdata/maria_data
chmod -R 777 /home/datum/data/logs/mariadb
执行mariadb初始化命令：
cd /etc/my.cnf.d/
MysqL_install_db --defaults-file=/etc/my.cnf --datadir=/home/datum/data/appdata/maria_data/dbdata/ --user=MysqL
启动mariadb(MysqL): service MysqL start
mariadb重置密码命令：MysqLadmin -u root password "123456"
允许远程登录： GRANT ALL PRIVILEGES ON *.* TO 'root'@'%'IDENTIFIED BY '123456' WITH GRANT OPTION; flush privileges;
其中，123456为root的密码。root密码设置完后，必须要重启MysqL才能生效
重启mariadb(MysqL): service MysqL restart
mariadb用户名密码登录命令： MysqL -uroot -p123456
允许远程登录： GRANT ALL PRIVILEGES ON *.* TO 'root'@'%'IDENTIFIED BY '123456' WITH GRANT OPTION; flush privileges;
其中，123456为root的密码
查看数据库： show databases;
切换数据库： use MysqL;
展示所有表： show tables;