LPI Linux Certification in a Nutshell (72 page)

1. What daemon is associated with the control files
   /etc/hosts.allow
   and
   /etc/hosts.deny
   ?
   

2. In general terms, describe a method to locate SUID programs in
   the local filesystem. Why might an administrator do this
   routinely?
   

3. What is the danger of making
   /bin/vi
   SUID?
   

4. Why should a user run
   ssh
   instead of
   telnet
   ?
   

5. Describe shadow passwords and the file where the passwords are
   stored. Why don’t we store encrypted password strings in
   /etc/passwd
   anymore?
   

6. How can the tool
   /usr/sbin/lsof
   help you
   identify potential security issues?
   

7. What is the difference between a hard limit and a soft limit,
   with regard to the
   ulimit
   command?
   

8. Why is it advisable to use
   sudo
   rather
   than
   su
   in an environment with multiple
   administrators?
   

9. What kinds of things can you ascertain about a remote system
   with the
   nmap
   command?
   

10. Describe the process of key-based authentication between
    systems using
    ssh
    .
    

11. What is the difference between a public and a private key?
    What are they used for?
    

12. Describe how to encrypt a file with
    gpg
    .
    

1. Use
   find
   as described in
   Chapter 22
   to locate SUID
   files. Is the list larger than you expected? Are the entries on your
   list justifiably SUID programs?
   

2. Create an entry in
   /etc/sudoers
   that lets your user account
   run any command as root. Run some commands through
   sudo
   and watch the file
   /var/log/messages
   . What entries do you
   see? How would this be useful in a multiadministrator
   environment?
   

3. Look at the file
   /etc/shadow
   . What user accounts do not
   have passwords? Why don’t they?
   

4. Experiment with the
   chage
   command to set
   the password age for your account.
   

5. Run
   ulimit –a
   . What default limits are
   set? What would be some useful limits to place on users?
   

6. Run
   netstat --tcp –anp | grep LISTEN
   .
   What processes on your system are listening on TCP ports? If you
   were to harden this system, how would you change this
   configuration?
   

7. Run
   nmap localhost
   . Does this output
   match what you saw from the previous
   netstat
   command? Why or why not?
   

8. If you have
   xinetd
   installed, go to the
   /etc/xinetd.d
   directory and
   determine what services are enabled.
   

9. Run
   ssh-keygen –t dsa
   . What files were
   created in
   ~/.ssh
   ? What are the
   permissions on those files?
   

On the Exam

Practice, practice, practice! The best way to get familiar with
Linux is by interacting with a working Linux system. Become familiar
with the command line and how to read logfiles. Nothing is hidden from
you in Linux; if you know where to look, simple tools such as
cat
,
ls
, and
grep
will tell you everything you need to know
about your system. Spend as much time as you can working hands-on with
a Linux system before you take the LPI 102 exam.

1. What environment variable holds the list of all directories that
   are searched by the shell when you type a command name?
   

   1. $LIST
      

   2. $VIEW
      

   3. $PATH
      

   4. $ENV
      

   5. None of the above
      

2. In the
   bash
   shell, entering the
   !!
command has the same effect as which one
   of the following (assuming
   bash
   is in emacs
   mode)?
   

   1. Ctrl-P and Enter
      

   2. Ctrl-N and Enter
      

   3. Ctrl-U and Enter
      

   4. !-2


   5. !2


3. Name the command that displays pages from the online user’s
   manual and command reference.
   

4. Which of the following commands displays the comments from a
   bash
   script? Select all that apply.
   

   1. find “^#” /etc/rc.d/rc.local
      

   2. sed ‘/^#/ !d’ /etc/init.d/httpd
      

   3. grep ^# /etc/init.d/httpd
      

   4. grep ^# /etc/passwd
      

   5. locate “^#” /etc/skel/.bashrc
      

5. Which one of the following answers creates an environment
   variable
   VAR1
, present in the
   environment of a
   bash
   child process?
   

   1. VAR1="fail" ; export VAR1
      

   2. VAR1="fail" \ export VAR1
      

   3. VAR1="fail"
      

   4. set VAR1="fail" ; enable VAR1
      

   5. export VAR1 \ VAR1="fail"
      

6. What SQL command is used to modify data present in a
   table?
   

   1. INSERT
      

   2. WHERE
      

   3. UPDATE
      

   4. OVERWRITE
      

   5. JOIN
      

7. What output will the following command generate:
   seq
   -s";" -w 1 10
   

   1. 01;02;03;04;05;06;07;08;09;10


   2. 1;2;3;4;5;6;7;8;9;10


   3. 1;10


   4. 01;02;03;04;05;06;07;08;09;010


   5. None of the above
      

8. Adam wants to protect himself from inadvertently overwriting
   files when copying them, so he wants to alias
   cp
   to prevent overwrite. How should he go about this? Select one.
   

   1. Put
      alias cp='cp -i'
in
      ~/.bashrc
      

   2. Put
      alias cp='cp -i'
in
      ~/.bash_profile
      

   3. Put
      alias cp='cp -p'
in
      ~/.bashrc
      

   4. Put
      alias cp='cp -p'
in
      ~/.bash_profile
      

   5. Put
      alias cp = 'cp -I'
in
      ~/.bashrc
      

9. Consider the following script, stored in a file with proper
   modes for execution:
   

   #!/bin/bash
   for $v1 in a1 a2
   do
   echo $v1
   done
   

   Which one of the following best represents the output produced
   on a terminal by this script?
   

   1. in


      a1


      a2


   2. a1


      a2


   3. $v1


      $v1


      $v1


   4. No output is produced, but the script executes
      correctly.
      

   5. No output is produced, because the script has an
      error.
      

10. Monica consults the
    /etc/passwd
    file
    expecting to find encrypted passwords for all of the users on her
    system. She sees the following:
    

    jdoe:x:500:500::/home/jdoe:/bin/bash
    bsmith:x:501:501::/home/bsmith:/bin/tcsh
    

    Which of the following is true? Select one.
    

    1. Accounts
       jdoe
       and
       bsmith
       have no passwords.
       

    2. Accounts
       jdoe
       and
       bsmith
       are disabled.
       

    3. The passwords are in
       /etc/passwd-
       .
       

    4. The passwords are in
       /etc/shadow
       .
       

    5. The passwords are in
       /etc/shadow-
       .
       

11. What is the main configuration file for X Windows?
    

    1. /etc/xorg.conf
       

    2. /etc/x11.conf
       

    3. /etc/X11/x11.conf
       

    4. /etc/X11/xorg.conf
       

    5. None of the above
       

12. What file in the user’s home directory will an X Windows
    application look to for configuration settings such as color and video
    mode?
    

    1. ~/.xinitrc
       

    2. ~/.xconfig
       

    3. ~/.Xresources
       

    4. ~/.xorg.conf
       

    5. ~/.bashrc
       

13. What is the protocol XDMCP used for?
    

    1. Remote logging of X Windows events.
       

    2. Remote control of a running X Windows display.
       

    3. Graphical login support for the local host.
       

    4. Graphical login support for remote hosts on the
       network.
       

    5. None of the above.
       

14. Which of the following are
    not
    commonly
    used display managers for X Windows? Choose two.
    

    1. xdm
       

    2. gdm
       

    3. kdm
       

    4. xfce
       

    5. X11
       

15. Emacspeak is:
    

    1. A popular text editor for Linux.
       

    2. A window manager.
       

    3. An assistive technology that handles screen reading for a
       number of console applications.
       

    4. An assistive technology that provides a user with an
       on-screen keyboard.
       

    5. None of the above.
       

16. Which one of the following outcomes results from the following
    command?
    

    #
    chmod g+s /home/software
    

    1. The SUID bit will be set for
       /home/software
       .
       

    2. The SGID bit will be set for
       /home/software
       , preventing access by those
       not a member of the
       software
       group.
       

    3. The SGID bit will be set for
       /home/software
       , to keep group membership of
       the directory consistent for all files created.
       

    4. The sticky bit will be set for
       /home/software
       .
       

    5. The sticky bit will be applied to all files in
       /home/software
       .
       

17. Which one of these files determines how messages are stored
    using
    syslogd
    ?
    

    1. /etc/sysconfig/logger.conf
       

    2. /etc/syslog.conf
       

    3. /etc/syslogd.conf
       

    4. /etc/conf.syslog
       

    5. /etc/conf.syslogd
       

18. Which MTA was designed specifically with security in
    mind?
    

    1. Sendmail
       

    2. Postfix
       

    3. Qmail
       

    4. Exim
       

    5. None of the above
       

19. Where are mail logs usually stored in a standard
    syslog
    setup?
    

    1. /var/log/messages
       

    2. /var/log/secure
       

    3. /var/log/dmesg
       

    4. /var/log/maillog
       

    5. /var/maillog
       

20. How many hosts can exist on a subnet with mask 255.255.255.128?
    Select one.
    

    1. 512
       

    2. 256
       

    3. 128
       

    4. 127
       

    5. 126
       

21. For an Internet workstation with a single network interface,
    what routes must be added to interface
    eth0
    after
    it is initialized? Select one.
    

    1. None
       

    2. Interface
       

    3. Interface and default gateway
       

    4. Interface, local network, and default gateway
       

22. On a Linux server, what service is most likely “listening” on
    port 25? Select one.
    

    1. Apache
       

    2. SSHd
       

    3. Postfix
       

    4. Samba
       

    5. FTP
       

23. Which one of these protocols is a Layer 4 connection-oriented
    protocol? Select one.
    

    1. TCP
       

    2. IP
       

    3. UDP
       

    4. ICMP
       

24. Which command will display information about Ethernet interface
    eth0
    ? Select one.
    

    1. cat /proc/eth/0
       

    2. ifconfig eth0
       

    3. ipconfig eth0
       

    4. ipconfig /dev/eth0
       

    5. cat /etc/eth0.conf
       

25. What does the
    printcap
    entry
    sd
indicate? Select one.
    

    1. The system default printer
       

    2. A printer’s spool directory
       

    3. A device file for the printer
       

    4. A location where errors are stored
       

    5. The printer driver
       

26. Which of the following is a valid entry in
    /etc/fstab
    for a remote NFS mount from server
    fs1
    ? Select one.
    

    1. fs1:/proc /mnt/fs1 nfs defaults 9
9


    2. /mnt/fs1 fs1:/proc nfs defaults 0
0


    3. fs1:/home /mnt/fs1 nfs defaults 0
0


    4. /mnt/fs1 fs1:/home nfs defaults 0
0


    5. /home:fs1 /mnt/fs1 nfs defaults 0
0


27. Which network protocol is used by SSH and FTP? Select
    one.
    

    1. ICMP
       

    2. UDP
       

    3. TCP
       

    4. DHCP
       

    5. PPP
       

28. Which of the following programs will display DNS information for
    a host? Choose all that apply.
    

    1. host
       

    2. nslookup
       

    3. nsstat
       

    4. dig
       

    5. ping
       

29. Which of the following statements regarding the ICMP protocol is
    not
    true? Select one.
    

    1. ICMP is connectionless.
       

    2. ICMP provides network flow control.
       

    3. ICMP is also known as UDP.
       

    4. ICMP is used by
       ping
       .
       

30. What server daemon resolves domain names to IP addresses for
    requesting hosts?
    

31. What function does a print filter serve? Select one.
    

    1. It collates output from multiple users.
       

    2. It translates various data formats into a page description
       language.
       

    3. It rejects print requests from unauthorized users.
       

    4. It rejects print requests from unauthorized hosts.
       

    5. It analyzes print data and directs print requests to the
       appropriate
       lpd
       .
       

32. Consider the following excerpt from the file
    /etc/resolv.conf
    on a Linux
    workstation
    :
    

    nameserver 127.0.0.1
    nameserver 192.168.1.5
    nameserver 192.168.250.2
    

    What can be said about this configuration? Select one.
    

    1. Two DNS servers on the public network are being used for
       resolution.
       

    2. One DNS server on the local network is being used for
       resolution.
       

    3. The configuration contains errors that will prevent the
       resolver from
       functioning
       .
       

    4. A caching-only nameserver is the first nameserver
       queried.
       

    5. The resolver library will consult
       nameserver 192.168.250.2
first.
       

33. Name the file that contains simple mappings between IP addresses
    and system names.
    

34. What program can be used to interactively change the behavior of
    a print queue? Select one.
    

    1. lpd
       

    2. lpr
       

    3. lpq
       

    4. lprm
       

    5. lpc
       

35. What program will display a list of each hop across the network
    to a specified destination? Select one.
    

    1. tracert
       

    2. rttrace
       

    3. traceroute
       

    4. routetrace
       

    5. init
       

36. What is the system-wide
    bash
    configuration
    file called? Include the entire path.
    

37. How can a nonprivileged user configure
    sendmail
    to forward mail to another account?
    Select one.
    

    1. She can add a new entry in
       /etc/aliases
       .
       

    2. She can create a
       .forward
       file
       containing the new address.
       

    3. She can create an
       .alias
       file
       containing the new address.
       

    4. She can create a
       sendmail.cf
       file
       containing the new address.
       

    5. She cannot forward mail without assistance from the
       administrator.