LPI Linux Certification in a Nutshell (35 page)

Why is the
/var
directory usually
located in a partition of its own?

As a system administrator for a network with many workstations
and a central NFS file server, how can you safely share
/usr
with your users while still maintaining
control of its contents?

What is the recommended size for a swap partition, as a
function of the memory in a system?

Describe how to create a
tar
archive and
how its contents are extracted.

In general terms, describe the procedure used to compile and
install free or open source software from source code.

What is a shared library? How can you determine what library
dependencies exist in a compiled executable?

How does your system know where to look for shared
libraries?

Briefly describe the major functional modes of
rpm
.

How do you add additional repositories to
yum
?

What are the reasons to choose LILO over GRUB as a boot
loader, or vice versa?

Why might a Debian Linux administrator use
dpkg
-iG
instead of simply
dpkg -i
to
install a package?

In a shell, examine your disk layout using
fdisk
. For example:

#
fdisk /dev/sda
Command (m for help):
p
Disk /dev/sda: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x0003bf13
Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          25      200781   83  Linux
/dev/sda2              26          89      514080   82  Linux swap / Solaris
/dev/sda3              90       24321   194643540   83  Linux

Is the entire disk consumed by the existing
filesystems?

Examine how system directories are mapped to disk partitions
on your system. Are
/var
and
/tmp
in their own partitions? Is
/boot
in its own partition within cylinder
1024? Is the root filesystem relatively small?

Download a
tarball (from
http://sourceforge.net
, for
example), and install it on your system with the following
steps:

Were there any difficulties with this procedure?

Use
ldd
to examine library dependencies
of executable programs on your system. For example:

#
ldd `which gcc`
linux-gate.so.1 => (0x00110000)
libc.so.6 => /lib/libc.so.6 (0x00682000)
/lib/ld-linux.so.2 (0x00663000)

Using a system that utilizes
dpkg
, obtain
a list of all packages installed under
dpkg
management with
dpkg -l | less
. Find a package
in the list that looks unfamiliar, and query information about the
package using
dpkg -s pkg_name
.

Using a system that utilizes RPM, obtain a list of all
packages installed under RPM management with
rpm -qa |
less
. Find a package in the list that looks unfamiliar,
and query information about the package using
rpm -qi
pkg_name
.

Using a system that utilizes RPM, obtain a list of all
available packages that you can install from the currently
configured repositories with
yum list available |
less.

Describe the difference between shell variables and
environment variables.

Compare and contrast built-in and explicitly defined commands
and those found in
$PATH
.

After a lengthy session of file manipulation on the command
line, what will
!ls
produce?

What files does
bash
read when you log
in?

Explain the notion of
pipes
as they refer
to shell capabilities, and illustrate using an example of two or
more filter programs.

Explain the
-p
option to
cp
and give an example of why it is
necessary.

Give two examples of files matched by the wildcard
??[!1-5]
.

Name the three standard I/O streams and their
functions.

Give an example of the redirection operator,
>
, and describe how the outcome would
be different using the
>>
operator.

What process is the parent of all system processes? Give both
the PID and the program name.

Name three common utilities used for process
monitoring.

What happens to a typical daemon when it receives
SIGHUP
? How would the behavior be
different if it received
SIGKILL
?

Compare and contrast background and foreground jobs, and state
the syntax to put a command in the background on the command
line.

What two classifications of characters make up regular
expressions?

How are the regular expressions
[A-Z]*
and
^[A-Z]*$
different?

What is the difference between executing
:q
versus
:q!
in
vi
?

What does it mean to put
vi
into
command mode
?

Start a
bash
shell in a console or
terminal window and enter the following
commands
:

$
MYVAR1="Happy"
$
MYVAR2="Birthday"
$
export MYVAR1
$
bash
$
echo $MYVAR1 $MYVAR2
$
exit
$
echo $MYVAR1 $MYVAR2

Continuing the previous exercise, press the up arrow until you
see the last
echo
command. Press the up arrow
again.

Still continuing the previous exercise, enter the command
!echo
. Does anything change as a result of the
revised
export
command?

The
file
command is used to examine a
file’s contents and displays the file type. Explain the result of
using
file
as follows:

$
cd / ; file `ls | head -10`

Execute this command on your system:

$
cut -d: -f1 /etc/passwd | fmt -w 20 | head -1

Execute the following
sed
substitution
command and explain why it might be used on
/etc/passwd
:

$
sed 's/:[^:]*:/:---:/' /etc/passwd | less

Execute this command:

$
cd /sbin ; ls -li e2fsck fsck.ext2

Execute the following command sequence and explain the result
at each step (this example assumes that
cp
is
not aliased to
cp -i
, which is a common default
alias):

$
cd
$
cp /etc/skel .
$
cp -r /etc/skel .
$
cp -rfv /etc/skel .
$
cp -rfvp /etc/skel .

Remove the directory created in the previous exercise, using
rmdir
and/or
rm
. Which
command can complete the task in a single step?

Explain when the wildcard
{htm,html}
might be useful.

Give an example of how the wildcard
*.[Tt][Xx][Tt]
could be used with
directory listings.

What can be said about filenames matched by the
*.?
wildcard?

Experiment with redirecting the output of
ls
as follows:

$
cp /etc/skel . 2> info.txt

Experiment with
ps, pstree
, and
top
to monitor active processes on your system.
Include
top
’s interactive commands.

If you have Apache running, use
ps
(and
perhaps
grep
) to identify the
httpd
process and its PID, which is owned by
root. Send that process the
HUP
signal as follows:

$
kill -SIGHUP
pid

Using
tail
, examine the Apache error log
(the location of your logfile may differ):

$
tail /var/log/httpd/error_log

What was the effect of
HUP
on Apache?

While running X, start some interactive processes in the
background and experiment with using
jobs
,
bg
, and
fg
. For
example:

$
firefox &
$
xterm &
$
emacs &
$
jobs
$
fg 1
$
fg 2...

Were you able to bring each of the jobs to the foreground
successfully?

This exercise starts a process, using various methods to view
and modify the process execution priority:

Start an editing session in the background using
nice
:

$
nice vi &

Observe that the process was
nice
’d using
ps
:

$
ps -u

Check it again using
top
:

$
top -i

Within
top, renice
the
vi
process using the
r
command and observe the effect on priority.

Exit
top
and use
renice
to set the nice value back to
zero.

Use a simple regular expression with
grep
to find
bash
users in
/etc/passwd
.

Examine the difference between grep and egrep by issuing the
following
commands
:

$
grep ".+:x:.+:/bin/bash$" /etc/passwd
$
egrep ".+:x:.+:/bin/bash$" /etc/passwd

How is the output of these commands different? Why?

Determine the number of empty lines in
/etc/inittab
.

Use
vi
to create a text file. Enter
insert mode
with
i
and insert text. Quit insert mode with
Esc and move around using
h
,
j
,
k
, and
l
, then re-enter insert mode and add more
text. End the session with
ZZ.
cat
the file. Is it as expected?