mysql问题

我的系统是redhat8.0去除原来的mysql后再重装二进至分发,解压后进入目录运行mysqld说找不到命令(command not found),其他命令也一样,但明明在啊.这是怎么回事?　　　　　　

运行mysql结果是
ERROR 2002: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
这　　　　　　

发现var/lib/mysql/mysql.sock不存在,请问如何建立?　　　　　　

chmod +x full-path-to-mysql/support-files/mysql.server (line 1)
cp full-path-to-mysql/support-files/mysql.server /etc/rc.d/init.d/mysqld (line 2)
/etc/rc.d/init.d/mysqld start (line 3)
echo "/etc/rc.d/init.d/mysqld start" >>/etc/rc.d/rc.local (auto start with linux) (line 4)　　　　　　

forget something:
   cp full-path-to-mysql/support-files/mys-medium.cnf /etc/my.cnf
   vi /etc/my.cnf to see the socket path,it should be /tmp/mysql.sock
  
vi /etc/profile
add this to the end:
   MYSQLDIR=/usr/local/mysql
   PATH=/usr/local/mysql/binPATH
   export MYSQLDIR PATH