Tag Archives | Linux system

How to secure your internet activity with Linux system and VPN

Hackers can access, steal and sell your online activity data as well as manipulate it if you don’t use the right system and tools. The level of protection you want will largely influence which tools and systems to use. With a Linux system and VPN, it becomes possible to hide your browsing tracks, personal information, and various other online activities. When you have the right protection in place, not even the government can access your activity. Keep reading to learn how businesses and individuals alike can use a Linux system and VPN for ongoing protection of their online data. We will also explore why this is important and why you should care about your online data. Hackers steal data for a number of reasons. Sometimes, it’s’ for their own purposes. Other times, they sell it or give it to other entities. These entities may or may not have known about the data collection processes the hackers use to gather the data.

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What Is a VPN?

VPN stands for virtual private network, which means it provides encryption, making it difficult for the bad guys to steal your data when visiting their sites. It also acts as an added layer of protection against the government from tracking your online activity.

In some areas, a VPN even grants users access to certain content that is not normally available in their geographical areas. Such forms of content often include video, international gaming, certain servers, etc.

The VPN works to protect your online activity by making it appear as if you are logged in from a different location. As soon as you connect to the VPN, you can set your location to anywhere in the world.

Additionally, with a Linux system, you can improve the safety and protection of your data thanks to advanced security measures. Fixes for Linux program exploits made by hackers are generally developed and released well before other operating systems develop and release fixes for their equivalent programs.

How Does a Linux System Make Online Activity More Secure?

Getting fixes to exploits is of the utmost importance in both personal and business settings, particularly those sitting on large amounts of data.

Hackers, crackers, and phreakers steal people’s online data all the time for multiple reasons. Some do it to fight a cause, some steal it unintentionally, some do it for fun, a few do it for commercial espionage or sabotage, and lastly, it’s not uncommon for disgruntled employees to steal data for whistle blowing purposes.

A Linux system helps avoid several types of attacks:

  • Reading data
  • Denial of service
  • Altering/manipulating data
  • Access to system

Tips for Increasing Data Protection With a Linux System

To increase data protection through the use of a Linux system, you must first pinpoint what you mean by “secure.” To do this, you must assess what you intend to do with the system and just how secure you need the data to be. In most cases, Linux systems need security, at a minimum, in the following areas:

  • Authorization: Do not allow ANYONE access to the system unless they NEED access
  • Verification: Make sure users have to go through a 2-step authentication process to verify their identity each time logging into the system
  • Integrity: All personal information must be protected and NEVER compromised
  • Non-repudiation: Must have proof of receipt of data; official receipt showing how you received the data and from whom
  • Privacy/confidentiality: You must abide by any privacy and confidentiality regulations such as the ISO 7984-2 International Standards Organization Security Standard
  • Availability: System must be able to perform its required function at all times during normal operating hours while maintaining security around the clock.

Choose a Native App

When installing a VPN on a Linux system, you will have two options: Open-source or native app. With a native app, you will get access to more features and less required configuration.

Because of this, it is highly suggested that any VPN you use at least comes in the form of a native client for Linux.

In addition to the dedicated app, users of a VPN that comes in the form of a native client enjoy sophisticated security, ultra-fast speeds, and the ability to run on a command-line interface. Additionally, the server list is always kept up to date, making it simple to download and switch between UDP to TCP over the Open VPN protocol.

Run Through Services and Customize Each of Them

When using Linux as a VPN, you will have several types of facilities to choose from, including mail and WWW. Linux handles some of these services through a system of ports.

Take for example Port 21, which controls FTP. You can check out service names in the /etc/services file for a map of port numbers.

It’s ideal to have most of your services running through a configuration file /etc/inetd.conf. You’ll also want to take a lot of time when running through this type of file as you will have the ability to customize how each of the available services is running and protected.

Keep Services in inetd.conf Turned OFF

Check the services in inetd.conf, and make sure they are not set to turn on by default. To achieve maximum security, you must turn them off. You can type the command netstat -vat to see which services are currently running on your Linux or alternatively, you can use ss command. For any services that you are unfamiliar with, make sure to look them up in /etc/inetd.conf.

Final Thoughts

There are numerous VPNs to choose from. The surfshark.com VPN is especially ideal for those who want to unblock lots of region-locked content from sources such as Netflix, Amazon Prime Video and Hulu.

Users of this VPN are also huge fans of their ability to connect to the VPN through an unlimited number of devices. This is an example of a VPN that has the features you should look for when researching for ways to use a Linux system to secure internet activity.


31+ Examples for sed Linux Command in Text Manipulation

In the previous post, we talked about bash functions and how to use them from the command line directly and we saw some other cool stuff. Today we will talk about a very useful tool for string manipulation called sed or sed Linux command. Sed is used to work with text files like log files, configuration files, and other text files. In this post, we are going to focus on sed Linux command which is used for text manipulation, which is a very important step in our bash scripting journey. Linux system provides some tools for text processing, one of those tools is sed. We will discuss the 31+ examples with pictures to show the output of every example.

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Understand sed Linux Command

The sed command is a non-interactive text editor. Sed Linux command edits data based on the rules you provide, you can use it like this:

sed options file

You are not limited to use sed to manipulate files, you apply it to the STDIN directly like this:

echo "Welcome to LikeGeeks page" | sed 's/page/website/'

sed Linux command

The s command replaces the first text with the second text pattern. In this case, the string “website” was replaced with the word “page”, so the result will be as shown.

The above example was a very basic example to demonstrate the tool. We can use sed Linux command to manipulate files as well.

This is our file:

sed manipulate file

sed 's/test/another test/' ./myfile

The results are printed to the screen instantaneously, you don’t have to wait for processing the file to the end.

If your file is huge enough, you will see the result before the processing is finished.

Sed Linux command doesn’t update your data. It only sends the changed text to STDOUT. The file still untouched. If you need to overwrite the existing content, you can check our previous post which was talking about redirections.

Using Multiple sed Linux Commands in The Command Line

To run multiple sed commands, you can use the -e option like this:

sed -e 's/This/That/; s/test/another test/' ./myfile

sed multiple commands

Sed command must be separated by a semicolon without any spaces.

Also, you can use a single quotation to separate commands like this:

sed -e '

> s/This/That/

> s/test/another test/' myfile

sed separate commands

The same result, no big deal. 

Reading Commands From a File

You can save your sed commands in a file and use them by specifying the file using -f option.

cat mycommands


s/test/another test/

sed -f mycommands myfile

read commands from file

Substituting Flags

Look at the following example carefully:

cat myfile

sed 's/test/another test/' myfile

sed substitute flag

The above result shows the first occurrence in each line is only replaced. To substitute all occurrences of a pattern, use one of the following substitution flags.

The flags are written like this:


There are four types of substitutions:

  • g, replace all occurrences.
  • A number, the occurrence number for the new text that you want to substitute.
  • p, print the original content.
  • w file: means write the results to a file.

You can limit your replacement by specifying the occurrence number that should be replaced like this:

sed 's/test/another test/2' myfile

sed number flag

As you can see, only the second occurrence on each line was replaced.

The g flag means global, which means a global replacement for all occurrences:

sed 's/test/another test/g' myfile

sed global flag

The p flag prints each line contains a pattern match, you can use the -n option to print the modified lines only.

cat myfile

sed -n 's/test/another test/p' myfile

sed supress lines

The w flag saves the output to a specified file:

sed 's/test/another test/w output' myfile

send output to file

The output is printed on the screen, but the matching lines are saved to the output file.

Replace Characters

Suppose that you want to search for bash shell and replace it with csh shell in the /etc/passwd file using sed, well, you can do it easily:

sed 's/\/bin\/bash/\/bin\/csh/' /etc/passwd

Oh!! that looks terrible.

Luckily, there is another way to achieve that. You can use the exclamation mark (!) as string delimiter like this:

sed 's!/bin/bash!/bin/csh!' /etc/passwd

Now it’s easier to read.

Limiting sed

Sed command processes your entire file. However, you can limit the sed command to process specific lines, there are two ways:

  • A range of lines.
  • A pattern that matches a specific line.

You can type one number to limit it to a specific line:

sed '2s/test/another test/' myfile

sed restricted

Only line two is modified.

What about using a range of lines:

sed '2,3s/test/another test/' myfile

replace range of lines

Also, we can start from a line to the end of the file:

sed '2,$s/test/another test/' myfile

sed replace to the end

Or you can use a pattern like this:

sed '/likegeeks/s/bash/csh/' /etc/passwd

sed pattern match


You can use regular expressions to write this pattern to be more generic and useful.

Delete Lines

To delete lines, the delete (d) flag is your friend.

The delete flag deletes the text from the stream, not the original file.

sed '2d' myfile

sed delete line

Here we delete the second line only from myfile.

What about deleting a range of lines?

sed '2,3d' myfile

delete multiple line

Here we delete a range of lines, the second and the third.

Another type of ranges:

sed '3,$d' myfile

delete to the end

Here we delete from the third line to the end of the file.

All these examples never modify your original file.

sed '/test 1/d' myfile

delete pattern match

Here we use a pattern to delete the line if matched on the first line.

If you need to delete a range of lines, you can use two text patterns like this:

sed '/second/,/fourth/d' myfile

delete range of lines

From the second to the fourth line are deleted.

Insert and Append Text

You can insert or append text lines using the following flags:

  • The (i) flag.
  • The  (a) flag.

echo "Another test" | sed 'i\First test '

sed insert text

Here the text is added before the specified line.

echo "Another test" | sed 'a\First test '

sed append

Here the text is added after the specified line.

Well, what about adding text in the middle?

Easy, look at the following example:

sed '2i\This is the inserted line.' myfile

sed insert line

And the appending works the same way, but look at the position of the appended text:

sed '2a\This is the appended line.' myfile

sed append line

The same flags are used but with a location of insertion or appending.

Modifying Lines

To modify a specific line, you can use the (c) flag like this:

sed '3c\This is a modified line.' myfile

sed modify line

You can use a regular expression pattern and all lines match that pattern will be modified.

sed '/This is/c Line updated.' myfile

sed pattern match

Transform Characters

The transform flag (y) works on characters like this:

sed 'y/123/567/' myfile

sed transform character

The transformation is applied to all data and cannot be limited to a specific occurrence.

Print Line Numbers

You can print line number using the (=) sign like this:

sed '=' myfile

sed line numbers

However, by using -n combined with the equal sign, the sed command displays the line number that contains matching.

sed -n '/test/=' myfile

hide lines

Read Data From a File

You can use the (r) flag to read data from a file.

You can define a line number or a text pattern for the text that you want to read.

cat newfile

sed '3r newfile' myfile

read data from file

The content is just inserted after the third line as expected.

And this is using a text pattern:

sed '/test/r newfile' myfile

read match pattern

Cool right?

Useful Examples

We have a file that contains text with a placeholder and we have another file that contains the data that will be filled in that placeholder.

We will use the (r) and (d) flags to do the job.

The word DATA in that file is a placeholder for a real content which is stored in another file called data.

We will replace it with the actual content:

Sed '/DATA>/ {

r newfile

d}' myfile

repalce placeholder

Awesome!! as you can see, the placeholder location is filled with the data from the other file.

This is just a very small intro about sed command. Actually, sed Linux command is another world by itself.

The only limitation is your imagination.

I hope you enjoy what’ve introduced today about the string manipulation using sed Linux command.

Thank you.