Mysql (errno: 13) can't find file frm

Recently got this error when I was trying to copy a database on to another server. I basically copied the mysql data directory for the corresponding database on to the new server and logged into mysql client.

mysql> select count(*) from placement; 
Can't find file: './main/placement.frm (errno: 13)

Checked the mysql log and this was being reported for the all frm files for all tables in the db. Looks like this is a permission issue on the data directory. Changed to the following permissions and it seemed to work.

server> sudo chmod -R 660 main
server> sudo chmod 775 main