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Answer the Investigation 4 question.
==Investigation 5: How do we turn system services on and off?==
{{Admon/note|Use fedora2|Perform these steps in the '''fedora2''' virtual machine.}}
{{Admon/important| Security Advice | We have seen that maintaining unneeded users and groups can be a security risk due to the unnecessary increase in the complexity of your system. Similarly, it is also unnecessarily hazardous, and even more so, to leave unneeded services running. In this investigation, we will learn how to control services, and turn off those that we think are not necessary.}}
1. Determine your current runlevel using the runlevel command.
2. Change to the appropriate startup directory in a terminal window. For example, if your runlevel is 4, change to /etc/rc.d/rc4.d
3. Record the names of the symbolic links in that directory.
4. Run the menu option System>Administration>Services. You will then see the Service Configuration screen.
5. Find the isdn service and select customize from the tool bar. and deselect the checkbox for your runlevel from step 1. Quit the app.
6. Return to the terminal window you used in Step 2. Get a listing of the symbolic links in the startup directory. Is it any different from what you recorded in Step 3?
7. Using the Service Configuration screen, reenable the isdn service.
8. Repeat step 6. What has changed this time?
9. Run this command:
chkconfig isdn off
10. Now what has changed in the directory?
11. Run this command:
chkconfig isdn on
12. Now what has changed?
13. Run the command:
chkconfig --list
What does the output show?
14. What is the relationship between the Service Configuration tool, the symbolic links in the startup directory, and the chkconfig command?
15. You can also set services to be on or off for certain runlevels. For example, to turn httpd on for runlevel 4, we issue the command:
chkconfig --level 4 httpd on
To turn it off, we type:
chkconfig --level 4 httpd off
16. To increase your computer's security, make sure these services are disabled:
anacron, bluetooth, cups, irda, irqbalance, isdn, mdmonitor, netfs, nfs, nfslock, pcscd, rpcgssd, rpcidmapd, rpcsvcgssd, sendmail, ypbind.
You should understand that while most services in this list are often not needed, or are needed under circumstances different than those which occur here, there may be situations in which some of them are required, and it may be up to you as an administrator to determine which services are needed, and which should be turned off.
17. Finally, make sure the gpm service runs in runlevel 3, but not in 5.
Answer the Investigation 5 question.
