I tried to import data through Sqoop using the following command.
sqoop import -connect jdbc:mysql://localhost/test_sqoop --username root --table test
but I got the connection refuse error.
And I found out I can't connect to mysql and got this error:
Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock'
And I also found out if I don't execute start-dfs.sh,mysql.sock exists in /var/lib/mysql/mysql.sock.  
After I executed start-dfs.sh,mysql.sock would be gone and I can't connect to mysql.  
Below is /etc/my.cnf configuration.
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
 
    