In order to practice in kafka, I created AWS instance and issued pem file. chmod 400 kafka.pem Joses-MacBook-Pro:Downloads joohyunyoon$ chmod 400 kafka.pem chmod 400 : Change Mode, Gives the user read permission, and removes all other permission. These permissions are specified in octal, the first char is for the user, second for the group and the third is for other. The high bit (4) is for read..