安装上mysql后，报 Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock'，试了网上的方法都没有用，于是打开/etc/my.cnf查看。
看到这么一段：
# The MySQL server
26 [mysqld]
27 port = 3306
28 socket = /tmp/mysql.sock
29 skip-external-locking
30 log-error=/alidata/log/mysql/error.log
31 key_buffer_size = 16M
32 max_allowed_packet = 1M
33 table_open_cache = 64
34 sort_buffer_size = 512K
35 net_buffer_length = 8K
36 read_buffer_size = 256K
37 read_rnd_buffer_size = 512K
38 myisam_sort_buffer_size = 8M
可知，使用的.sock文件，是/tmp/mysql.sock，而不是/var/run/mysqld/mysqld.sock，于是加个链接
ln -s /tmp/mysql.sock /var/run/mysqld/mysqld.sock
解决