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WHAT YOU NEED TO KNOW TO GET STARTED WITH LINUX

November 13, 2020

This article has been just updated: November 13, 2020


AN OVERVIEW OF THE LINUX OS FOR NEWBIES

There may come a time in your computing life when you either desire or require a
degree of knowledge regarding the Linux operating system. You might decide to
explore Linux as an alternative operating system for your home computer. In some
cases, you may need to display some proficiency with the software in order to
perform your job. That’s how I first got involved with Linux.

After being introduced to the Linux machine that I would be using as a backup
and recovery server, I began searching for information to help me survive. There
is a wealth of informative websites, and over time I became more comfortable
maneuvering around the system.

This overview is intended to get you started with Linux. It is not meant as an
exhaustive reference guide. I will be providing links which offer more depth
pertaining to the various aspects of the OS that are discussed in this guide.

So without further ado, let’s plunge into the workings of the Linux operating
system.

 


WHAT IS LINUX?

Linux was born in 1991 as a free and open source alternative to Unix, according
to opensource.com. Its creator was Linus Torvalds, and due to a file structure
that held the distribution code in a directory called “Linux”, the name stuck.
The server admin had simply appended the first letter of Linus’ name to the word
Unix in an attempt to easily identify where the code was stored. Names can be
derived from the strangest places.

Linux is free for anyone to use and is distributed under the GPLv2 license. It
is a comprehensive operating system that has found many applications in diverse
areas of the computing landscape. You can find Linux running on supercomputers
as well as on small, embedded devices. Different Linux distributions are
tailored to be more useful in various implementations.


 


COMPONENTS OF THE LINUX OPERATING SYSTEM

There are a number of distinct pieces which comprise a distribution of the Linux
OS. According to linux.com, they are:

The Bootloader – This software manages the computer’s boot process.

The Kernel – The kernel is the core of the system and takes care of managing the
computer’s CPU, memory, and peripheral devices.

Daemons – Background services such as printing and scheduling are handled by
daemons.

The Shell – Also known as the Linux command line, in the early days of the
operating system this was the only way to control your computer. It required
commands to be entered in a text interface. Modern, desktop implementations of
Linux have made it possible to use the operating system without having to master
the command line.

Graphical Server – This sub-system is responsible for displaying the graphics on
your machine and is called the X server.

Desktop Environment – There are many different desktop environments such as
GNOME, Cinnamon, and KDE. This is the window through which the user interacts
with the operating system.

Applications – There are thousands of applications that can be downloaded and
installed to extend to functionality of your Linux implementation. Some Linux
distributions offer a centralized method for installing applications.

 


COMMONLY USED LINUX COMMANDS

Before we dive deeper into the inner workings of Linux, let’s take a look at
some of the commands which you will commonly need to execute when working with
the operating system through the command line. These are just a few of the more
than 1,000 Linux commands that are available. For further information and more
commands, consult the linuxtrainingacademy.com.

 * ls – This is the list directory command and displays the contents of the
   current working directory. Using the variant ls -l gives long form
   information and ls -a also will show you any hidden files in the directory.
 * pwd – The current working directory is displayed with this command.
 * cd – Change to your home directory with this command. Appending a space and a
   name will switch you to the named directory. Appending two periods will bring
   you to the current directory’s parent directory.
 * mkdir – You can create a new directory with this command as long as none
   already exist with the selected name.
 * mv – Rename or move files and directories with this command.
 * uname – This command displays information regarding the machine name and
   operating system. Use uname -a to obtain more detailed information.
 * history – Using this command you can see a list of the recently executed
   commands entered through the command line.
 * touch – You can create a file that does not already exist with this command.
   If the file exists, the timestamp is updated, but the contents remain
   unchanged.
 * chmod – This command is used to change the read, write and execute file
   permissions.
 * more – This is a very helpful command that displays multiple pages of
   information one screen at a time. Hitting enter will show you the next
   screen.
 * locate – Find a file’s location by name with this command.
 * man – Short for manual, this command displays the reference manual pages for
   a specified command. Entering man ls will show what the manual has on the ls
   command.
 * kill – This is used to kill a process by name.
 * ip – This displays and manages routing, devices, and can be used to assign an
   IP address to a specific interface.
 * grep – You can search for a specified pattern or string in files with this
   command.
 * du – This command displays disk space usage of files in a directory.
 * cp – Use this command to copy files and directories from one location to
   another.
 * passwd – This command allows you to create or update passwords for user
   accounts.
 * cat – You can view and add to a text file with this command.
 * sudo – This is a very powerful command that allows an authorized user to
   execute commands as the root user of the system.
 * vim/vi – Executing this command allows you to edit text and program files.

That’s enough to get you started. As we mentioned above, there are many commands
incorporated into Linux. Consult the training link supplied to further
investigate the functionality built into the operating system.

 


THE LINUX FILE STRUCTURE

The Linux operating system has an extensive default directory structure.
According to linux.com, these are the directories that can be found by executing
the “tree -L 1 /“ command. The directories we will be discussing are the top
level directories located under the root directory. We will simply name the
directories and state the contents that they hold.

 * /bin – contains binaries which are some of the applications and programs that
   can be executed.
 * /boot – files required for system startup are in this directory.
 * /dev – this virtual directory contains device files associated with
   peripheral devices attached to your system.
 * /etc – contains system-wide configuration files.
 * /home – users’ personal directories are located here.
 * /lib – as you might suspect, this directory contains libraries that contain
   the code required by the system’s applications.
 * /media – external storage is automatically mounted in the directory when it
   is plugged into your system.
 * /mnt – used to manually mount storage devices or partitions.
 * /opt – this directory will often contain software that you have compiled.
 * /proc – another virtual directory that contains information about your CPU
   and Linux kernel.
 * /root – home directory of the superuser or administrator.
 * /run – used to store temporary data from system processes.
 * /sbin – contains binaries that only the superuser will need.
 * /usr – this directory was used for users’ home directories but has been
   replaced by the /home directory for that purpose. Modern Linux distributions
   use the directory for various application and service-related files.
 * /srv – contains data for servers.
 * /sys – a virtual directory that contains device information.
 * /tmp – used for storing temporary files from users and applications.
 * /var – logs and task spools are found in this directory.

There may be additional directories at the root level that are part of your
particular Linux distro. Linux also creates subdirectories in most of the
directories we have referenced above. You can explore them by using commands
such as pwd, ls, and cd.


 


LINUX FILES AND FILE PERMISSIONS

The ability of users and applications to access files and directories is based
on their file permissions. In Linux, if you don’t have permission to use a file
in a particular way, it’s not going to happen. According to booleanworld.com,
these are the specific permissions that a file or directory can possess.

Read – Read permission enables the user to view the contents of a file and
view the names of files contained in a directory. Write – Having write
permission lets a user modify or delete a file. Combined with the execute
permission, you can modify the contents of a directory. Execute – Execute
permission lets you execute a file if the read permission is also enabled. It is
used with the write permission for modifying directories and the files they
contain.

Linux further delineates the control a user can exercise over a file or
directory by the use of groups. A group is a collection of zero or more users
that may have common computing requirements. File and directory permissions are
assigned to three entities:

User – these permissions impact the file’s owner.
Group – these permissions affect the group that owns the file. When the owner is
in the group, User permissions are enforced.
Other – all other users are subject to these permissions.

Executing a ls -l command will return a list of files and their permissions. The
file mode describes the type of entity and its permissions. It is ten characters
long, with the first letter being a ‘d’ for a directory, a ‘-‘ for a file, or a
‘l’ for a link.



The next nine characters symbolically spell out the permissions for the User,
Group, and Others respectively. Triplets of letters represent the permissions.
For example, this would give everyone read, write, and execute permission for a
file:

rwxrwxrwx

Where this takes away execute permission for the group and others.

rwxrw-rw-

So the letter indicates the permission is enabled and a dash shows it is not
set. They are always assigned in the read, write, and execute order.

Permissions can also be represented as numeric values based on binary
substitution of the characters.

 


LINUX SERVICES, DAEMONS, AND DEVICES

Linux services and daemons are very similar animals. They are both essentially
applications that run the background. They are not under the direct control of a
user. System events may initiate action by the services or daemons.

Some examples of important daemons are:

cron – used to schedule command execution
lpd – manage printing
rpc.mountd – respond to mount requests

Linux services such as Apache and MySQL are likely to be running on your
machine.



Devices files are special files that interact with device drivers to access
hardware attached to your system. They are found in the /dev directory.

 


NETWORKING WITH LINUX

Linux machines are often employed as network gateways or firewalls. The
reliability of the operating system, its cost-effectiveness, and its flexibility
make it a prime candidate for use in servers and devices involved in networking.
There are Linux distributions that are tailored to the needs of network
administrators.

According to geekflare.com, here are some of the more useful Linux networking
commands.

 * ifconfig – used to configure the parameters of network interfaces
 * telnet – tests connectivity between two hosts
 * netstat – allows you to review network connections
 * scp – used to copy files securely between hosts
 * nmap – checks opened ports

There are several Linux serial console programs which can be used for purposes
such as testing and configuring the serial ports in your network installations.
Among them are minicom, grub, and getty. Based on your specific distribution,
additional tools may be available for use in network administration.

 


A SAMPLE LINUX SESSION

Now that you have a little background concerning Linux let’s take a look at how
a typical session begins. We will use the command line for demonstration
purposes, but many Linux distributions have intuitive user-interfaces that can
be used to perform many of the same functions. We will see some of the concepts
discussed above in action.

Here’s what we are going to do.

Log into the system, locate a file, run it, change permissions so no-one else
can run it, and then log off. Let’s get started.

login username <enter> – Your username should have been assigned by your system
administrator. You will be prompted for your password. Provide it and hit enter
again.

You should be in your home directory. To verify, execute the pwd command. We are
going to assume that the program you are going to run is located in
/home/username/progs. Let’s go there by entering this command:

cd /home/username/progs
ls -l

Now you are presented with all of the files that are in the /home/username/prog
directory. You will see the file permissions, file owner, and group owner with
the file name on the far right.

You have a program titled myTestProgram which currently has permissions set at
–rwxrwxrwx, meaning that anyone can read, modify, and execute the program.

Since you are one of everyone, you can run it by simply typing its name and
hitting enter.

myTestProgram

Let’s assume that the program executed, but there is an issue you need to
resolve before letting anyone else use it. You need to change the permissions
with the chmod command as in this example:

chmod u=rwx,g=r,o=r myTestProgram

The result of this command is that only you can run the program. A look at the
file permissions will show this:

-rwxr—r—

Everyone else can only read the file. Now you can take your time and fix it
before modifying permissions again to let others use your creation.

You can simply logout to end your session.

logout

That’s it. You have successfully run a program in Linux and modified it so it
cannot be used by others. With a little practice, you will soon be moving around
the system like a pro.

 


INSTALLING LINUX

You may be interested in trying Linux on a particular computer but not yet be
ready to blow away the current operating system. Many Linux versions have what
is called a “live” distribution, where you can run the OS from a CD or other
external media without any changes to your hard drive.



This lets you check it out before making any commitment.

Once you are satisfied that the operating system indeed fits your needs, simply
click on the install icon and a software wizard will guide you during
installation. The wizard will help you determine if your machine meets the
minimum requirements for the OS. You will also set up your wireless connection
if you have one, as you will need to access the network to download additional
software and updates.

Further details on trying and installing Linux can be found on this page at
linux.com.

--------------------------------------------------------------------------------

This overview provides a taste of what to expect from the Linux operating
system. While it was once considered the operating system of experts or computer
geeks, the newer, user-friendly distributions allow just about anyone to
experiment with this powerful operating system. The links that are included in
this article are a good starting point if you desire more thorough Linux
knowledge. You just might find that Linux fills all of your computing needs and
lets you escape from the monolithic major operating system vendors.

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