Workshop

A UNIX security and file permissions is a reasonably large topic, and I touch on it in Hour 18. To answer
your question, though, it’s likely that the file or directory belongs to a group that you do not belong to.
Look at the group on the file using ls -la and add yourself to that group.
Q We’ve recently gotten a new Internet Service Provider, and all of our IP numbers have changed.
Now, every time I boot my UNIX system, I get “NFS Server Belboz not responding.” What’s going
on?
A It’s likely that the Belboz system is only listed in the /etc/hosts file of the UNIX system. View
the file, and you’ll likely see that the TCP/IP number is wrong; change it to the new number.
Q I hear that UNIX is less secure than other operating systems. True?
A No. UNIX’s problem is that it is more configurable than other operating systems, which means that
sometimes it’s misconfigured and is therefore less secure. Also, the level of knowledge about the
internals of UNIX is pretty high—source code is available for some implementations, which allows
hackers to probe for security holes in programs. Actually, even though Windows NT doesn’t have source
code publicly available, holes have been found in programs there. Just like any operating system, UNIX
has several problematic, widespread server programs—such as sendmail—that have caused
widespread publicity and security panics, but these have always been patched rather quickly.
Quiz
1. True or false? Root access is needed to use all networking commands in UNIX.
2. What does NFS stand for?
A. Network File Server
B. Nothing Falls Slowly
C. Network Failure System
D. Network File System
3. True or false? named does not use inetd as a receptionist server; named runs on its own, all
the time, and is not invoked each time a user asks for it.
4. True or false? Linux is the only available free or low-cost UNIX flavor.
5. The difference between a UNIX server and a UNIX workstation is usually what?
A. Different software
B. Different bandwidth
C. Different taste in restaurants
D. Different hardware
6. It’s most desirable to __________ when you encounter a problem with a UNIX service.
A. Start and stop a process
B. Reboot
C. Call the police
D. Ping