I have to change an RSA key file (.pem)'s permissions to 400 so I can use it to connect to an AWS EC2 instance but for some reason I cannot seem to do so. I am in the folder where the file is located and the command sudo chmod 400 3dcitydb.pem gives no output but has no effect on the file.
I even logged in as root and I still cannot do it:
root@ib:/media/isaac/Data/MOSS_application/aws_keys# sudo chmod 400 ./3dcitydb.pem
root@ib:/media/isaac/Data/MOSS_application/aws_keys# ls -l
total 4
-rwxrwxrwx 1 isaac isaac 1692 Jul 4 21:13 3dcitydb.pem
Any idea of what this could be? Any time I try to search this I either get people mistyping the chmod command, people unable to do so on an external hard drive due to a different partition system or people who didn't realize they had to change the file permissions in the first place.
Ubuntu version is 16.04
