Aug 182010

RSH and RLogin aren’t that difficult to set up once you’ve gone through the man pages and done the installation a few times, but those first few times are a pain. They’re old and insecure, but still frequently used on small compute clusters. I get the impression that a lot of beginners get stuck fiddling with them for hours or days. They’re quite possibly the biggest stumbling block one faces when setting up a compute cluster by hand (setting /etc/hosts.equiv, setting /root/.rhosts, making sure the right flags are being sent to the rsh and rlogin daemons, etc).

Both use the xinetd daemon, which is one of those carry-overs from ancient Unix. Plenty of old Unix stuff made sense, but inetd is backwards. To enable a service, you set disabled = no. To disable a service, you set disabled = yes.

Putting double negatives in your configuration file is not a good idea. When a setting this basic takes a couple seconds of thought, you’re doing it wrong. Were it something more complicated, administrators would be selecting the wrong option all the time.

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