Linux permission denied

The chmod 775 is an essential command that assigns read, write, and execute permission to a specific user, group, or others .

So 654 would mean read and write for owner, read and execute for group and only read for everyone else .

755 means read and execute access for everyone and also write access for the owner of the file . When you perform chmod 755 filename command you allow everyone to read and execute the file, the owner is allowed to write to the file as well.