1) What is Linux and why is it so popular?
Linux is an
operating system based on UNIX, and was first introduced by Linus Torvalds
commonly used in servers.It is based on the Linux Kernel, and can run on
different hardware platforms manufactured by Intel, MIPS, HP, IBM, SPARC and
Motorola. Another popular element in Linux is its mascot, a penguin figure
named Tux.
Popularity
of Linux is because of the following reasons
It is free
and open source. We can download Linux for free and customize it as per our
needs.
It is very
robust and adaptable.
Immense
amount of libraries and utilities
2) What is the difference between UNIX and LINUX?
Unix
originally began as a propriety operating system from Bell Laboratories, which
later on spawned into different commercial versions. On the other hand, Linux
is free, open source and intended as a non-propriety operating system for the
masses.
3) What is
BASH?
BASH is
short for Bourne Again SHell. It was written by Steve Bourne as a replacement
to the original Bourne Shell (represented by /bin/sh). It combines all the
features from the original version of Bourne Shell, plus additional functions
to make it easier and more convenient to use. It has since been adapted as the
default shell for most systems running Linux.
4) What is Linux Kernel?
The Linux
Kernel is a low-level systems software whose main role is to manage hardware
resources for the user. It is also used to provide an interface for user-level
interaction.
5) What is LILO?
LILO is a
boot loader for Linux. It is used mainly to load the Linux operating system
into main memory so that it can begin its operations.
6) What is a swap space?
A swap space
is a certain amount of space used by Linux to temporarily hold some programs
that are running concurrently. This happens when RAM does not have enough
memory to hold all programs that are executing.
7) What is the advantage of open source?
Open source
allows you to distribute your software, including source codes freely to anyone
who is interested. People would then be able to add features and even debug and
correct errors that are in the source code. They can even make it run better,
and then redistribute these enhanced source code freely again. This eventually
benefits everyone in the community.
8 ) What are the basic components of Linux?
Just like
any other typical operating system, Linux has all of these components: kernel,
shells and GUIs, system utilities, and application program. What makes Linux
advantageous over other operating system is that every aspect comes with additional
features and all codes for these are downloadable for free.
9) Does it help for a Linux system to have multiple desktop
environments installed?
In general,
one desktop environment, like KDE or Gnome, is good enough to operate without
issues. It’s all a matter of preference for the user, although the system
allows switching from one environment to another. Some programs will work on
one environment and not work on the other, so it could also be considered a
factor in selecting which environment to use.
10) What is the basic difference between BASH and DOS?
The key
differences between the BASH and DOS console lies in 3 areas:
- BASH
commands are case sensitive while DOS commands are not;
- under
BASH, / character is a directory separator and \ acts as an escape character.
Under DOS, / serves as a command argument delimiter and \ is the directory
separator
- DOS
follows a convention in naming files, which is 8 character file name followed
by a dot and 3 character for the extension. BASH follows no such convention.
11) What is the importance of the GNU project?
This
so-called Free software movement allows several advantages, such as the freedom
to run programs for any purpose and freedom to study and modify a program to
your needs. It also allows you to redistribute copies of a software to other
people, as well as freedom to improve software and have it released to the
public.
12) Describe the root account.
The root
account is like a systems administrator account, and allows you full control of
the system. Here you can create and maintain user accounts, assigning different
permissions for each account. It is the default account every time you install
Linux.
13) What is CLI?
CLI is short
for Command Line Interface. This interface allows user to type declarative
commands to instruct the computer to perform operations. CLI offers an
advantage in that there is greater flexibility. However, other users who are
already accustom with using GUI find it difficult to remember commands
including attributes that come with it.
14) What is GUI?
GUI, or
Graphical User Interface, makes use of images and icons that users click and
manipulate as a way of communicating with the computer. Instead of having to
remember and type commands, the use of graphical elements makes it easier to
interact with the system, as well as adding more attraction through images,
icons and colors.
15) How do you open a command prompt when issuing a command?
To open the
default shell (which is where the command prompt can be found), press
Ctrl-Alt-F1. This will provide a command line interface (CLI) from which you
can run commands as needed.
16) How can you find out how much memory Linux is using?
From a
command shell, use the “concatenate” command: cat /proc/meminfo for memory
usage information. You should see a line starting something like: Mem:
64655360, etc. This is the total memory Linux thinks it has available to use.
17) What is typical size for a swap partition under a Linux
system?
The
preferred size for a swap partition is twice the amount of physical memory
available on the system. If this is not possible, then the minimum size should
be the same as the amount ofmemory installed.
18) What are symbolic links?
Symbolic
links act similarly to shortcuts in Windows. Such links point to programs,
files or directories. It also allows you instant access to it without having to
go directly to the entire pathname.
19) Does the Ctrl+Alt+Del key combination work on Linux?
Yes, it
does. Just like Windows, you can use this key combination to perform a system
restart. One difference is that you won’t be getting any confirmation message
and therefore, reboot is immediate.
20) How do you refer to the parallel port where devices such as
printers are connected?
Whereas
under Windows you refer to the parallel port as the LPT port, under Linux you
refer to it as /dev/lp . LPT1, LPT2 and LPT3 would therefore be referred to as
/dev/lp0, /dev/lp1, or /dev/lp2 under Linux.
21) Are drives such as harddrive and floppy drives represented
with drive letters?
No. In
Linux, each drive and device has different designations. For example, floppy
drives are referred to as /dev/fd0 and /dev/fd1. IDE/EIDE hard drives are
referred to as /dev/hda, /dev/hdb, /dev/hdc, and so forth.
22) How do you change permissions under Linux?
Assuming you
are the system administrator or the owner of a file or directory, you can grant
permission using the chmod command. Use + symbol to add permission or – symbol
to deny permission, along with any of the following letters: u (user), g
(group), o (others), a (all), r (read), w (write) and x (execute). For example
the command chmod go+rw FILE1.TXT grants read and write access to the file
FILE1.TXT, which is assigned to groups and others.
23) In Linux, what names are assigned to the different serial
ports?
Serial ports
are identified as /dev/ttyS0 to /dev/ttyS7. These are the equivalent names of
COM1 to COM8 in Windows.
24) How do you access partitions under Linux?
Linux
assigns numbers at the end of the drive identifier. For example, if the first
IDE hard drivehad three primary partitions, they would be named/numbered,
/dev/hda1, /dev/hda2 and /dev/hda3.
25) What are hard links?
Hard links
point directly to the physical file on disk, and not on the path name. This
means that if you rename or move the original file, the link will not break,
since the link is for the file itself, not the path where the file is located.
26) What is the maximum length for a filename under Linux?
Any filename
can have a maximum of 255 characters. This limit does not include the path
name, so therefore the entire pathname and filename could well exceed 255
characters.
27) What are the filenames that are preceded by a dot?
In general,
filenames that are preceded by a dot are hidden files. These files can be
configuration files that hold important data or setup info. Setting these files
as hidden makes it less likely to be accidentally deleted.
28) Explain virtual desktop.
This serves
as an alternative to minimizing and maximizing different windows on the current
desktop. Using virtual desktops, each desktop is a clean slate where you can
open one or more programs. Rather than minimizing/restoring all those programs
as needed, you can simply shuffle between virtual desktops with programs intact
in each one.
29) How do you share a program across different virtual desktops
under Linux?
To share a
program across different virtual desktops, in the upper left-hand corner of a
program window look for an icon that looks like a pushpin. Pressing this button
will “pin” that application in place, making it appear in all virtual desktops,
in the same position onscreen.
30) What does a nameless (empty) directory represent?
This empty
directory name serves as the nameless base of the Linux file system. This
serves as an attachment for all other directories, files, drives and devices.
31) What is the pwd command?
The pwd
command is short for print working directory command. It’s counterpart in DOS
is the cd command, and is used to display the current location in the directory
tree.
32) What are daemons?
Daemons are
services that provide several functions that may not be available under the
base operating system. Its main task is to listen for service request and at
the same time to act on these requests. After the service is done, it is then
disconnected and waits for further requests.
33) How do you switch from one desktop environment to another,
such as switching from KDE to Gnome?
Assuming you
have these two environments installed, just log out from the graphical
interface. Then at the Log in screen, type your login ID and password and
choose which session type you wish to load. This choice will remain your
default until you change it to something else.
34) What are the kinds of permissions under Linux?
There are 3
kinds of permissions under Linux:
- Read:
users may read the files or list the directory
- Write:
users may write to the file of new files to the directory
- Execute:
users may run the file or lookup a specific file within a directory
35) How does case sensitivity affect the way you use commands?
When we talk
about case sensitivity, commands are considered identical only if every
character is encoded as is, including lowercase and uppercase letters. This
means that CD, cd and Cd are three different commands. Entering a command using
uppercase letters, where it should be in lowercase, will produce different
outputs.
36) What are environmental variables?
Environmental
variables are global settings that control the shell’s function as well as that
of other Linux programs. Another common term for environmental variables is
global shell variables.
37) What are the different modes when using vi editor?
There are 3
modes under vi:
- Command
mode – this is the mode where you start in
- Edit mode
– this is the mode that allows you to do text editing
- Ex mode –
this is the mode wherein you interact with vi with instructions to process a
file
38) Is it possible to use shortcut for a long pathname?
Yes, there
is. A feature known as filename expansion allows you do this using the TAB key.
For example, if you have a path named /home/iceman/assignments directory, you
would type as follows: /ho[tab]/ice[tab]/assi[tab] . This, however, assumes
that the path is unique, and that the shell you’re using supports this feature.
39) What is redirection?
Redirection
is the process of directing data from one output to another. It can also be
used to direct an output as an input to another process.
40) What is grep command?
grep a
search command that makes use of pattern-based searching. It makes use of
options and parameters that is specified along the command line and applies
this pattern into searching the required file output.
41) What could possibly be the problem when a command that was
issued gave a different result from the last time it was used?
One highly
possible reason for getting different results from what seems to be the same
command has something to do with case sensitivity issues. Since Linux is case
sensitive, a command that was previously used might have been entered in a
different format from the present one. For example, to lists all files in the
directory, you should type the command ls, and not LS. Typing LS would either
result in an error message if there is no program by that exact name exist, or
may produce a different output if there is a program named LS that performs
another function.
42) What are the contents in /usr/local?
It contains
locally installed files. This directory actually matters in environments where
files are stored on the network. Specifically, locally-installed files go to
/usr/local/bin, /usr/local/lib, etc.). Another application of this directory is
that it is used for software packages installed from source, or software not
officially shipped with the distribution.
43) How do you terminate an ongoing process?
Every
process in the system is identified by a unique process id or pid. Use the kill
command followed by the pid in order to terminate that process. To terminate
all process at once, use kill 0.
44) How do you insert comments in the command line prompt?
Comments are
created by typing the # symbol before the actual comment text. This tells the
shell to completely ignore what follows. For example: “# This is just a comment
that the shell will ignore.”
45) What is command grouping and how does it work?
You can use
parentheses to group commands. For example, if you want to send the current
date and time along with the contents of a file named OUTPUT to a second file
named MYDATES, you can apply command grouping as follows: (date cat OUTPUT)
> MYDATES
46) How do you execute more than one command or program from a
single command line entry?
You can
combine several commands by separating each command or program using a
semicolon symbol. For example, you can issue such a series of commands in a
single entry:
ls –l cd ..
ls –a MYWORK
which is
equivalent to 3 commands:
ls -l
cd..
ls -a MYWORK
**Note that
this will be executed one after the other, in the order specified.
47) Write a command that will look for files with an extension
“c”, and has the occurrence of the string “apple” in it.
Answer: Find
./ -name “*.c” | xargs grep –i “apple”
48) Write a command that will display all .txt files, including
its individual permission.
Answer: ls
-a -l *.txt
49) Write a command that will do the following:
-look for
all files in the current and subsequent directories with an extension c,v
-strip the,v
from the result (you can use sed command)
-use the
result and use a grep command to search for all occurrences of the word ORANGE
in the files.
Find ./
-name “*.c,v” | sed ‘s/,v//g’ | xargs grep “ORANGE”
50) What, if anything, is wrong with each of the following
commands?
a) ls -l-s
b) cat
file1, file2
c) ls – s
Factdir
Answers:
a) there
should be space between the 2 options: ls -l -s
b) do not
use commas to separate arguments: cat file1 file2
c) there
should be no space between hyphen and option label: ls –s Factdir
