13–32 CompTIA Linux+ Certification, Powered by LPI
Unit summary: Security
Topic A In this topic, you learned that Linux provides various commands that you can use to
manage users on your system. You learned how to block logins for all non-root users
and for specific users. You learned how to list open files associated with a user,
process, device, and so forth. You limited resources available to a user with the ulimit
command. Finally, you examined the security options made available by the Pluggable
Authentication Module (PAM) subsystem.
Topic B In this topic, you learned that the Linux kernel includes IP routing support. You
learned about routing tables and how to modify them to configure a computer as a
router. You also learned about iptables network filtering, which enables you to
configure your computer to operate as a firewall. You learned how to scan for services
and ports on your system using netstat and nmap. And, you learned various ways to
disable unneeded services. Finally, you learned about third-party network security
1 What is the difference between the last and lastb commands?
The last command displays a list of the last successfully logged-on users. The lastb command
displays a list of the last failed logon attempts.
2 True or false? The lock command is the standard command on all Linux
distributions for locking your screen when you are idle.
False. The true command is the gnome screensaver command --lock. Your system might have an
alias for that command named lock.
3 What file do you create to prevent all non-root users from logging in to a system?
4 Which command do you use to list the files opened by a user, process, or daemon?
5 What is the purpose of the ulimit command?
To limit the resources that a user may consume, such as the maximum number of processes he
or she may start.
6 You configure PAM (Pluggable Authentication Module) preferences by editing the
7 What is a default gateway?
The primary router for your network segment.
8 IP forwarding is the same as __________.