chmod 000 will make the file/s readable only by root.
You need to provide more details.
if you did something like chmod -R 000 / then you probably need to boot with an installation media and change the permissions to its original state (for the files managed by RPM it will be easy for others impossible unless you know).
If you haven't fixed this yet, you could try this:
for p in $(rpm -qa); do rpm --setperms $p; done
It would go through all installed rpm packages and set permissions back to what the rpm originally provided. Good Luck!