#how to useradd

[quicklings]

As a Cucumber Game Changer

[narliee]

Imogen keeps on sending me couples costume ideas.

[miwtual]

@yellowjacketsnetwork event 05 — growth @lgbtqcreators creator challenge — past event (growth) — aaron schwartz, on the other side of grief with ocean vuong (insp)

[innovativeacademy-blog]

SYSTEM ADMIN INTERVIEW QUESTIONS 24-25

Table of Content

Introduction

File Permissions

User and Group Management:

Cron Jobs

System Performance Monitoring

Package Management (Red Hat)

Conclusion

Introduction

The IT field is vast, and Linux is an important player, especially in cloud computing. This blog is written under the guidance of industry experts to help all tech and non-tech background individuals secure interviews for roles in the IT domain related to Red Hat Linux.

File Permissions

Briefly explain how Linux file permissions work, and how you would change the permissions of a file using chmod. In Linux, each file and directory has three types of permissions: read (r), write (w), and execute (x) for three categories of users: owner, group, and others. Example: You will use chmod 744 filename, where the digits represent the permission in octal (7 = rwx, 4 = r–, etc.) to give full permission to the owner and read-only permission to groups and others.

What is the purpose of the umask command? How is it helpful to control default file permissions?umask sets the default permissions for newly created files and directories by subtracting from the full permissions (777 for directories and 666 for files). Example: If you set the umask to 022, new files will have permissions of 644 (rw-r–r–), and directories will have 755 (rwxr-xr-x).

User and Group Management:

Name the command that adds a new user in Linux and the command responsible for adding a user to a group. The Linux useradd command creates a new user, while the usermod command adds a user to a specific group. Example: Create a user called Jenny by sudo useradd jenny and add him to the developer’s group by sudo usermod—aG developers jenny, where the—aG option adds users to more groups without removing them from other groups. 

How do you view the groups that a user belongs to in Linux? 

The group command in Linux helps to identify the group a user belongs to and is followed by the username. Example: To check  user John’s group: groups john

Cron Jobs

What do you mean by cron jobs, and how is it scheduled to run a script every day at 2 AM? 

A cron job is defined in a crontab file. Cron is a Linux utility to schedule tasks to run automatically at specified times. Example: To schedule a script ( /home/user/backup.sh ) to run daily at 2 AM: 0 2 * * * /home/user/backup.sh Where 0 means the minimum hour is 2, every day, every month, every day of the week.

How would you prevent cron job emails from being sent every time the job runs? 

By default, cron sends an email with the output of the job. You can prevent this by redirecting the output to /dev/null. Example: To run a script daily at 2 AM and discard its output: 0 2 * * * /home/user/backup.sh > /dev/null 2>&1   

System Performance Monitoring

How can you monitor system performance in Linux? Name some tools with their uses. 

Some of the tools to monitor the performance are: Top: Live view of system processes and usage of resource htop: More user-friendly when compared to the top with an interactive interface. vmstat: Displays information about processes, memory, paging, block IO, and                CPU usage. iostat: Showcases Central Processing Unit (CPU) and I/O statistics for devices and partitions. Example: You can use the top command ( top ) to identify processes consuming too much CPU or memory.

In Linux, how would you check the usage of disk space?

The df command checks disk space usage, and Du is responsible for checking the size of the directory/file. Example: To check overall disk space usage:  df -h The -h option depicts the size in a human-readable format like GB, MB, etc.

Package Management (Red Hat)

How do you install, update, or remove packages in Red Hat-based Linux distributions by yum command?

In Red Hat and CentOS systems, the yum package manager is used to install, update, or remove software. Install a package:  sudo yum install httpd This installs the Apache web server.  Update a package: sudo yum update httpd Remove a package:sudo yum remove httpd 

By which command will you check the installation of a package on a Red Hat system?

The yum list installed command is required to check whether the package is installed. Example: To check if httpd (Apache) is installed:  yum list installed httpd

Conclusion

The questions are designed by our experienced corporate faculty which will help you to prepare well for various positions that require Linux such as System Admin.

Contact for Course Details – 8447712333

[sockupcloud]

How To Setup Elasticsearch 6.4 On RHEL/CentOS 6/7?

What is Elasticsearch? Elasticsearch is a search engine based on Lucene. It is useful in a distributed environment and helps in a multitenant-capable full-text search engine. While you query something from Elasticsearch it will provide you with an HTTP web interface and schema-free JSON documents. it provides the ability for full-text search. Elasticsearch is developed in Java and is released as open-source under the terms of the Apache 2 license. Scenario: 1. Server IP: 192.168.56.101 2. Elasticsearch: Version 6.4 3. OS: CentOS 7.5 4. RAM: 4 GB Note: If you are a SUDO user then prefix every command with sudo, like #sudo ifconfig With the help of this guide, you will be able to set up Elasticsearch single-node clusters on CentOS, Red Hat, and Fedora systems. Step 1: Install and Verify Java Java is the primary requirement for installing Elasticsearch. So, make sure you have Java installed on your system. # java -version openjdk version "1.8.0_181" OpenJDK Runtime Environment (build 1.8.0_181-b13) OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode) If you don’t have Java installed on your system, then run the below command # yum install java-1.8.0-openjdk Step 2: Setup Elasticsearch For this guide, I am downloading the latest Elasticsearch tar from its official website so follow the below step # wget https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.4.2.tar.gz # tar -xzf elasticsearch-6.4.2.tar.gz # tar -xzf elasticsearch-6.4.2.tar.gz # mv elasticsearch-6.4.2 /usr/local/elasticsearch Step 5: Permission and User We need a user for running elasticsearch (root is not recommended). # useradd elasticsearch # chown -R elasticsearch.elasticsearch /usr/local/elasticsearch/ Step 6: Setup Ulimits Now to get a Running system we need to make some changes of ulimits else we will get an error like “max number of threads for user is too low, increase to at least ” so to overcome this issue make below changes you should run. # ulimit -n 65536 # ulimit -u 2048 Or you may edit the file to make changes permanent # vim /etc/security/limits.conf elasticsearch - nofile 65536 elasticsearch soft nofile 64000 elasticsearch hard nofile 64000 elasticsearch hard nproc 4096 elasticsearch soft nproc 4096 Save files using :wq Step 7: Configure Elasticsearch Now make some configuration changes like cluster name or node name to make our single node cluster live. # cd /usr/local/elasticsearch/ Now, look for the below keywords in the file and change according to you need # vim conf/elasticsearch.yml cluster.name: kapendra-cluster-1 node.name: kapendra-node-1 http.port: 9200 to set this value to your IP or make it 0.0.0.0 ID needs to be accessible from anywhere from the network. Else put your IP of localhost network.host: 0.0.0.0 There is one more thing if you have any dedicated mount pint for data then change the value for #path.data: /path/to/data to your mount point.

Your configuration should look like the above. Step 8: Starting Elasticsearch Cluster As the Elasticsearch setup is completed. Let the start Elasticsearch cluster with elastic search user so first switch to elastic search user and then run the cluster # su - elasticsearch $ /usr/local/elasticsearch/bin/elasticsearch 22278 Step 9: Verify Setup You have all done it, just need to verify the setup. Elasticsearch works on port default port 9200, open your browser to point your server on port 9200, You will find something like the below output http://localhost:9200 or http://192.168.56.101:9200 at the end of this article, you have successfully set up Elasticsearch single node cluster. In the next few articles, we will try to cover a few commands and their setup in the docker container for development environments on local machines. Read the full article

[qcs01]

Automating RHEL Tasks with Shell Scripting

Introduction

Red Hat Enterprise Linux (RHEL) is a powerful and versatile operating system used widely in enterprise environments. One of its greatest strengths lies in the ability to automate repetitive tasks using shell scripting. This article will cover the basics of shell scripting, how to write and execute scripts, common use cases for automation, and tips for creating efficient scripts.

Basics of Shell Scripting

Shell scripting allows you to automate commands that you would normally run in a terminal. The most common shell used in RHEL is Bash (Bourne Again Shell).

1. Creating a Shell Script

To create a shell script, start by creating a new file with a .sh extension:

nano myscript.sh

2. Writing the Script

Begin your script with the shebang (#!) followed by the path to the shell interpreter:

#!/bin/bash

echo "Hello, RHEL!"

3. Making the Script Executable

Before you can run your script, you need to make it executable:

chmod +x myscript.sh

4. Executing the Script

You can run your script by typing:

./myscript.sh

Common Use Cases for Automation

1. System Monitoring

Automate system monitoring tasks to keep an eye on resource usage, disk space, and running processes.

#!/bin/bash

# Check disk space

df -h

# Check memory usage

free -m

2. Backup and Restore

Automate backup processes to ensure your data is safely stored and easily retrievable.

#!/bin/bash

# Backup important files

tar -czvf backup.tar.gz /path/to/important/files

3. User Management

Automate the creation and deletion of users, as well as setting permissions.

#!/bin/bash

# Add a new user

useradd newuser

# Set a password for the user

echo "newuser:password" | chpasswd

4. Software Installation and Updates

Automate the installation and updating of software packages.

#!/bin/bash

# Update all packages

yum update -y

# Install a specific package

yum install -y httpd

Tips for Creating Efficient Scripts

Use Comments: Comment your code to explain what each part of the script does. This makes it easier to understand and maintain.

# This script checks disk space and memory usage

df -h

free -m

     2. Error Handling: Implement error handling to make your scripts more robust.

if [ $? -ne 0 ]; then

  echo "An error occurred"

  exit 1

fi

    3. Variables: Use variables to store values that are used multiple times in your script.

# Define variables

BACKUP_DIR="/path/to/backup"

tar -czvf $BACKUP_DIR/backup.tar.gz /path/to/important/files

   4. Loops: Use loops to perform repetitive tasks efficiently.

# Loop through a list of directories and create backups

for DIR in /home /var/log /etc; do

  tar -czvf $DIR-backup.tar.gz $DIR

done

   5. Functions: Use functions to organize your code into reusable blocks.

# Define a function

check_disk_space() {

  df -h

}

# Call the function

check_disk_space

Conclusion

Shell scripting is a powerful tool for automating tasks in RHEL, making it easier to manage systems and perform routine tasks efficiently. By understanding the basics, common use cases, and best practices, you can harness the full potential of shell scripting to streamline your workflows and improve productivity.

For more details www.hawkstack.com 

[hollandweb]

These days, graphical user interfaces rule our screens. As such, the command line may appear to be a thing of the past. It is still a powerful tool, though, for anyone who wants to fully utilise a computer's potential. Greetings from the Linux command line universe. Here, we will uncover the tips and tricks that can transform you from a casual user into a command line maestro. Essential Command Line Basics for Linux We'll lay the groundwork for your exploration of the Linux command line in this article. In order to make sure you are comfortable using the terminal and carrying out commands successfully, we will start with the fundamentals. Open a Terminal You can use the terminal application that comes with most Linux distributions. Usually, you can locate it by looking for "Terminal" in the Applications menu or using the system search bar. Basic Commands: ls: List files and directories in the current directory. bashCopy code ls cd: Change the current directory. bashCopy code cd Documents pwd: Print the current working directory. bashCopy code pwd mkdir: Create a new directory. bashCopy code mkdir NewFolder touch: Create an empty file. bashCopy code touch myfile.txt Navigating the File System: Using cd to navigate through directories. bashCopy code cd .. Using ls to list the contents of a directory. bashCopy code ls /home/user/Documents File Manipulation: cp: Copy files or directories. bashCopy code cp file.txt /path/to/destination/ mv: Move or rename files or directories. bashCopy code mv oldfile.txt newfile.txt rm: Remove files or directories. bashCopy code rm myfile.txt Viewing File Content: cat: Display the entire content of a file. bashCopy code cat myfile.txt less or more: View file contents one screen at a time. bashCopy code less myfile.txt head and tail: Show the first or last few lines of a file. bashCopy code head myfile.txt File Permissions: Use chmod to change file permissions. bashCopy code chmod 755 myscript.sh chown changes the owner of a file or directory. bashCopy code sudo chown user:group myfile.txt File Searching: find: Search for files and directories. bashCopy code find /path/to/search -name "*.txt" grep: Search for text within files. bashCopy code grep "keyword" myfile.txt Managing Users and Permissions: passwd: Change your password. bashCopy code passwd sudo: Execute a command with superuser privileges. bashCopy code sudo command useradd and userdel: Add and delete user accounts. bashCopy code sudo useradd newuser sudo userdel olduser Help and Manuals: To get help for a command, use the --help option. bashCopy code ls --help Use the man command to access comprehensive manuals. bashCopy code man ls Keyboard Shortcuts: Up and Down arrow keys for command history. Tab key for auto-completion. Package Management: For Debian/Ubuntu systems (using apt): bashCopy code sudo apt update sudo apt upgrade For CentOS/RHEL systems (using yum): bashCopy code sudo yum update These examples should help you get started with the Linux command line and understand how to perform basic operations. How to Use the Linux Command Line Productively We're going to look at some methods and resources that will help you work with the Linux command line environment more effectively and efficiently. Therefore, mastering these abilities is crucial to optimising your workflow and developing your command-line skills. Tab Completion in Linux command line By pressing the "Tab" key, you can quickly and efficiently complete file and directory names, command names, and other arguments in the Linux command line thanks to a powerful feature called tab completion. It saves you time and prevents you from manually typing lengthy and possibly mistake-prone names. Here's how tab completion functions and some advice on how to use it efficiently: File and Directory Names: When you start typing the name of a file or directory, you can press the "Tab" key to autocomplete it.

If there's a single matching option, it will be completed for you. If there are multiple matching options, pressing "Tab" twice will display a list of all possible matches for you to choose from. For example, if you have files named "file1.txt" and "file2.txt," and you type cat f and then press "Tab," it will complete to cat file. Command Names: Tab completion also works for command names. When you start typing a command, pressing "Tab" will attempt to complete it. If you press "Tab" twice, it will list all available commands that match what you've typed so far. For example, if you start typing su and press "Tab," it might complete to sudo or sum. Pressing "Tab" twice will show you all available commands that start with "su." Directory Paths: Tab completion works with directory paths as well. You can start typing a directory path, and it will complete both directory names and the path itself. For example, if you want to navigate to the "/var/www" directory, you can type cd /v and then press "Tab" to autocomplete to cd /var/. Options and Arguments: Tab completion can also help you complete command options and arguments. For example, if you type ls -l /ho and press "Tab," it can autocomplete to ls -l /home/. Custom Tab Completion: You can create custom tab completion scripts or functions for specific commands or tasks. These scripts can provide tab-completable options and arguments based on your needs. Custom tab completion scripts are typically stored in files like /etc/bash_completion.d/ or loaded in your shell's profile configuration (e.g., .bashrc or .zshrc). Escaping Spaces: If you have spaces in your file or directory names, you can use backslashes or quotes to escape them. For example, if you have a file named "my file.txt," you can type cat my\ file.txt or cat "my file.txt" to use tab completion. Linux Command History and Recall Ever use a command only to find yourself in need of it again a short while later? Command history and recall allow you to quickly access commands that you have already run. A list of recent commands, each with a number attached, is displayed by the history command. An exclamation point (!) followed by the command number can be used to rerun a command (e.g.,!42 will rerun the 42nd command in your history). By pressing Ctrl + R and then entering a keyword from the command you're looking for, you can also search your command history. By using this feature, you can avoid typing lengthy, intricate commands again. Using Aliases in the Linux Shell Aliases are like custom shortcuts for your commands. You can create your own shorthand for frequently used or complex commands. For example, if you often find yourself typing ls -l to list files in long format, you can create an alias like this: bashCopy code alias ll='ls -al' After creating the alias, you can use ll instead of ls -al to list files. Linux Command Line Shortcuts Command line shortcuts are quick key combinations that help you navigate, edit, and control your terminal more efficiently. Here are a few essential shortcuts: Keyboard Shortcut Description CTRL + A Moves the cursor to the beginning of the line. CTRL + E Moves the cursor to the end of the line. CTRL + U Deletes text from the cursor to the beginning of the line. CTRL + K Deletes text from the cursor to the end of the line. CTRL + L Clears the terminal screen. CTRL + C Interrupts (stops) the current command. CTRL + D Exits the current shell or terminal session. CTRL + Z Suspends the current command (resumable with the fg command). Pipelines and Redirections in Linux command line Pipelines and redirections are powerful features in the Linux command line that allow you to manipulate input and output streams of commands, enabling you to perform complex tasks efficiently. Here's some examples of pipelines and redirections: Pipelines (|): Pipelines allow you to chain multiple commands together, passing the output of one command as the input to another.

This can be incredibly useful for processing and transforming data on the fly. For example, let's say you have a list of files in a directory, and you want to find all the files that contain a specific keyword: bashCopy code grep "keyword" *txt In this example, grep searches for the keyword in all txt files in the current directory. However, if you want to narrow down the results to only show the filenames containing the keyword, you can use a pipeline: bashCopy code grep -l "keyword" *txt | xargs -I basename Here, the grep command searches for the keyword and uses the -l option to list only the filenames. The | symbol passes this list of filenames to xargs, which then extracts the basename of each file, giving you a cleaner list of matching filenames. Redirections (>, >>, : Redirects the output of a command to a file, overwriting the file if it already exists. bashCopy code echo "Hello, world!" > output.txt >>: Redirects the output of a command to a file, but appends it to the file if it already exists. bashCopy code echo "Appended text" >> output.txt and 2>>: Redirects standard error (stderr) output to a file, overwriting or appending as needed. bashCopy code command_that_generates_error 2> error.log command_that_generates_error 2>> error.log Combining Redirection and Pipelines: You can combine redirection and pipelines to perform more complex operations. For instance, you can redirect the output of a command into a file and then use that file as input for another command. For example, you can sort the lines in a file and save the sorted result to another file: bashCopy code sort < input.txt > sorted_output.txt These are just a few Linux command line examples for pipelines and redirections. These facilitate data manipulation and process automation by enabling you to carry out an extensive array of tasks with efficiency and flexibility. Searching and Manipulating Text in the Linux Terminal Let us look at powerful tools and techniques available in the Linux command line for searching and manipulating text. These skills are useful in parsing log files, extracting specific information, and performing various text-related tasks efficiently. Searching for Text: grep: grep is a versatile command-line tool for searching text in files. It's often used with regular expressions for more complex searches. Basic usage: bashCopy code grep "pattern" file.txt Using regular expressions: bashCopy code grep -E "pattern1|pattern2" file.txt find: The find command is used to search for files and directories based on various criteria, including text content. Searching for files containing a specific text: bashCopy code find /path/to/search -type f -exec grep -l "pattern" \; ag (The Silver Searcher): An alternative to grep, ag is faster and more efficient for searching large codebases. Install it if it's not already available on your system. Basic usage: bashCopy code ag "pattern" /path/to/search Text Manipulation: sed (Stream Editor): sed is a powerful tool for text manipulation and transformation. It can be used to replace text, delete lines, and perform other operations. Replace text in a file: bashCopy code sed 's/old_text/new_text/g' file.txt awk: awk is a versatile text-processing tool that allows you to perform operations on text data, including filtering, formatting, and calculations. Print specific columns from a file: bashCopy code awk 'print $1, $3' file.txt cut: The cut command is used to remove sections from lines of files. Extract specific columns from a file: bashCopy code cut -d' ' -f1,3 file.txt sort: The sort command is used to sort lines in text files. Sorting a file alphabetically: bashCopy code sort file.txt uniq: uniq is used to remove duplicate lines from a sorted file. Removing duplicate lines from a sorted file: bashCopy code sort file.txt | uniq tr (Translate): tr is used for character-level text manipulation, such as translating or deleting characters.

Translate characters to uppercase: bashCopy code tr '[:lower:]' '[:upper:]' < file.txt cut and paste: The cut and paste commands can be used together to manipulate columns of text. Combining columns from two files: bashCopy code cut -f1 file1.txt > col1.txt cut -f2 file2.txt > col2.txt paste col1.txt col2.txt > combined.txt These are just a few examples of the many text-processing commands available in the Linux terminal. Depending on your specific needs, you can combine these commands and use them in scripts to perform more complex text manipulation tasks. Linux System Information and Troubleshooting In this chapter, we will explore essential tools and techniques for gathering system information, troubleshooting common issues, and monitoring resource usage in a Linux environment. These skills are convenient for maintaining system health and resolving problems effectively. Checking System Information (uname, df, free) To gain insights into your system’s configuration and resource utilization, you can use a variety of commands: Command Description Example uname Displays basic system information such as the kernel version and system architecture. Uname -a df Shows disk space usage, including information about disk partitions and their available space. df -h free Displays memory (RAM) usage information, including total, used, and available memory. free -m Linux System Logs and Troubleshooting (journalctl, dmesg) Troubleshooting system issues often involves examining logs and messages. Two key commands for this purpose are: – journalctl: The journalctl command provides access to the systemd journal, which contains logs for various system services and events. This tool enables you to view and filter log entries, making it invaluable for diagnosing system issues. To display recent system logs: bashCopy code journalctl -xe – dmesg: Additionally the dmesg command displays kernel ring buffer messages, which can be useful for diagnosing hardware-related problems. It specifically shows messages related to hardware detection, driver initialization, and system boot. To view kernel messages: bashCopy code dmesg | less Monitoring Resource Usage (htop) htop is an interactive and feature-rich process viewer and system monitor. Furthermore, it provides a real-time overview of system resource usage, including CPU, memory, and processes. It looks like this: To install htop use the following command: Debian/Ubuntu: bashCopy code sudo apt update sudo apt install htop CentOS/RHEL: bashCopy code sudo yum install epel-release # This is needed for EPEL repository on CentOS/RHEL 7 and earlier. sudo yum install htop Fedora: bashCopy code sudo dnf install htop htop is an excellent alternative to the basic top command. In addition, it offers a more user-friendly interface and additional features for monitoring and managing processes and system resources. How to Customize the Linux Terminal (color schemes, fonts) Customizing the Linux terminal can make your command-line experience more enjoyable and efficient. Here are several ways to customize the terminal to suit your preferences: Customizing the Prompt (PS1): To customize your command prompt, you can modify the PS1 environment variable in your shell configuration file (e.g., .bashrc for Bash). Here's an example of a custom Bash prompt: bashCopy code # Add the following line to your .bashrc file PS1='\[\e[32m\]\u@\h\[\e[m\]:\[\e[34m\]\w\[\e[m\]\$ ' \u displays the username. \h displays the hostname. \w displays the current working directory. \[\e[32m\] and \[\e[m\] change text color (in this case, green for the username and blue for the directory). Customizing Terminal Colors: Most terminal emulators allow you to customize text and background colors in their preferences. For example, in GNOME Terminal, you can navigate to "Edit" > "Preferences" > "Profiles" and click the "Edit" button for your profile. There, you can customize colors under the "Text" and "Background" tabs.

Aliases: Create aliases for frequently used commands or command sequences. Here's an example: bashCopy code # Add the following line to your .bashrc file alias ll='ls -al' After adding this alias, you can use ll in the terminal to list files and directories in long format with hidden files. Customizing Tab Completion: You can create custom tab completion behavior for specific commands. For example, let's create a simple completion for a custom script named my_script: bashCopy code # Add the following lines to your .bashrc file _my_script_completion() COMPREPLY=($(compgen -W "option1 option2 option3" -- "$COMP_WORDS[COMP_CWORD]")) complete -F _my_script_completion my_script This completion script suggests options ("option1," "option2," "option3") when you tab-complete my_script in the terminal. Customizing Key Bindings: You can customize key bindings in your shell by adding entries to your shell's configuration file. For example, to bind the Ctrl+L key combination to clear the terminal screen: bashCopy code # Add the following line to your .bashrc file bind -x '"\C-l": clear' After adding this line, pressing Ctrl+L will clear the terminal screen. Using Oh My Zsh or Powerline: If you're using Zsh, you can install Oh My Zsh or Powerline to customize your prompt and add plugins. Here's how to install Oh My Zsh: bashCopy code sh -c "$(curl -fsSL https://raw.github.com/ohmyzsh/ohmyzsh/master/tools/install.sh)" After installation, you can change the Zsh theme and customize plugins in the ~/.zshrc file. Using a Custom Terminal Font: You can change your terminal font through your terminal emulator's settings. For example, in GNOME Terminal, go to "Edit" > "Preferences" > "Profiles" > "Text" to select a custom font.

[edumotivation1]

Today you will learn how to create users in Linux using the useradd command.

As a Linux administrator, it is your responsibility to create users and groups, manage password policy and its aging, look at account expiries, and so on.

I believe that user and group management is one of the tasks that a Linux administrator has to do every day, that is why he has to have complete knowledge of commands like useradd, usermod, userdel, groupadd, gpasswd, id Command, and so on.

Suggested Read: How to use the id command in Linux

In this article, I am explaining the complete features of the useradd command and in future articles, I will publish the article above other user and group management commands.

So let’s get to the topic.

Linux is a multipurpose operating system. This means that you can log in with as many users as you want and do your work.

Key features of useradd command:

Create new users

Set Specific User ID (UID) and Group ID (GID)

Can set specific expiry date

Change default user configuration

Create a new user with a changed Home Directory

Create a new user without Home Directory

Add user to multiple Secondary/Supplementary groups

Create a new user with Specific Login Shell

Can set custom comments

Syntax:

You must follow the syntax given below to use the useradd command.

useradd [OPTIONS] USERNAME

[zdevops]

Mainframe Community / Mattermost

So, last night I ‘launched’ a MatterMost instance on https://mainframe.community. To summarize MatterMost (via wikipedia) it is: an open-source, self-hostable online chat service with file sharing, search, and integrations. It is designed as an internal chat for organisations and companies, and mostly markets itself as an open-source alternative to Slack[7][8] and Microsoft Teams. In this post I wanted to quickly explain how and why I did this. Let’s start with the why first. But Why? Last week, while working for one of my clients, I discovered they are starting to implemen MatterMost as a cross-team collaboration tool. And I discovered it has integrations, webhooks and bots. Being the Mainframe nerd I am, I quickly whipped up some lines of REXX to call CURL so I could ‘post’ to a MatterMost channel straight from The Mainframe. It was also quite easy in the wsadmin scripts to have jython execute an os.system to call curl and do the post... Now I wanted to take it a step further and create a “load module” that did the same, but could be called from a regular batch-job to, I donno, post messages when jobs failed, or required other forms of attention. Seeing as I was going to develop that on my own ZPDT/ZD&T I needed a sandbox environment. Running MatterMost locally from docker was a breeze, yet not running as “https” (something I wanted to test to work from the still to be made load-module. So, seeing as I already had the “mainframe.community”-domain, I thought, why not host it there, and use that as a sandbox....turned out that was easier done than imagined. But How? The instructions provided at https://docs.mattermost.com/install/install-ubuntu-1804.html were easy enough to follow and should get you up and running yourself in under an hour.

Seeing as there already ‘some stuff’ running at the local datacenter here I already had an nginx-environment up and running. I started with creating a new VM in my ProxMox environment (running Ubuntu 18.04) and made sure this machine got a static IP. From there on I did the following:

sudo apt update sudo apt upgrade sudo apt install postgresql postgresql-contrib

That then made sure the VM had a local database for all the MatterMost things. Initializing the DB environment was as easy as;

sudo --login --user postgres psql postgres=# CREATE DATABASE mattermost; postgres=# CREATE USER mmuser WITH PASSWORD 'x'; postgres=# GRANT ALL PRIVILEGES ON DATABASE mattermost to mmuser; postgres=# \q exit

Of course the password is not ‘x’ but something a bit more secure...

Then, make a change to the postgres config (vi /etc/postgresql/10/main/pg_hba.conf) changing the line

local   all             all                        peer

to

local   all             all                        trust

Then installing mattermost was basically these next commands:

  systemctl reload postgresql   wget https://releases.mattermost.com/5.23.1/mattermost-5.23.1-linux-amd64.tar.gz   mv mattermost /opt   mkdir /opt/mattermost/data   useradd --system --user-group mattermost   chown -R mattermost:mattermost /opt/mattermost   chmod -R g+w /opt/mattermost   vi /opt/mattermost/config/config.json   cd /opt/mattermost/   sudo -u mattermost ./bin/mattermost   vi /opt/mattermost/config/config.json   sudo -u mattermost ./bin/mattermost   vi /lib/systemd/system/mattermost.service   systemctl daemon-reload   systemctl status mattermost.service   systemctl start mattermost.service   curl http://localhost:8065   systemctl enable mattermost.service   restart mattermost   systemctl restart mattermost

Some post configuration needed to be done via the MatterMost webinterface (that was running like a charm) and then just a little nginx-config like specified at the MatterMost docs webpages and it was all up and running. Thanks to the peeps at LetsEncrypt it’s running TLS too :) Curious to see how ‘busy’ it will get on the mainframe.community. I’ve setup the VM with enough hardware resource to at least host 2000 users. So head on over to https://mainframe.community and make me ‘upgrade’  the VM due to the user growth :)

[linuxtech-blog]

How To Create a Sudo User on Linux (CentOS)

The sudo command is designed to allow users to run programs with the security privileges of another user, by default the root user.

In this guide, we will show you how to create a new user with sudo privileges on CentOS. You can use the sudo user to perform administrative tasks on your CentOS machine without a need to logging in as the root user.

Creating Sudo User

By default on CentOS, users in the group wheel are granted with sudo access. If you want to configure sudo for an existing user, just add your user to the wheel group, as shown in step 4.

Follow the steps below to create a sudo user on your CentOS server:

1. Log in to your server

Start by logging in to your CentOS server via ssh as the root user:

ssh root@server_ip_address

2. Create a new user account

Create a new user account using the useradd command:

useradd username

Replace username with the user name that you want to create.

3. Set the user password

Run the passwd command to set a password for the new user:

passwd username

You will be prompted to confirm the password. Make sure you use a strong password.

Changing password for user username. New password: Retype new password: passwd: all authentication tokens updated successfully.

4. Add the new user to the sudo group

By default on CentOS systems, members of the group wheel are granted with sudo access. Add the new user to the wheel group:

usermod -aG wheel username

How to use Sudo

Switch to the newly created user:

su - username

To use sudo, simply prefix the command with sudo and space.

sudo [COMMAND]

For example, to list the contents of the /root directory you would use:

sudo ls -l /root

The first time you use sudo from this account, you will see the following banner message and you will be prompted to enter the password for the user account.

We trust you have received the usual lecture from the local System Administrator. It usually boils down to these three things: #1) Respect the privacy of others. #2) Think before you type. #3) With great power comes great responsibility. [sudo] password for username:

Conclusion

That’s all. You have successfully created a sudo user on your CentOS system. You can now use this user to perform administrative tasks on your server.

Feel free to leave a comment if you have any questions.The sudo command is designed to allow users to run programs with the security privileges of another user, by default the root user.In this guide, we will show you how to create a new user with sudo privileges on CentOS. You can use the sudo user to perform administrative tasks on your CentOS machine without a need to logging in as the root user.Creating Sudo UserBy default on CentOS, users in the group wheel are granted with sudo access. If you want to configure sudo for an existing user, just add your user to the wheel group, as shown in step 4.Follow the steps below to create a sudo user on your CentOS server:1. Log in to your serverStart by logging in to your CentOS server via ssh as the root user:ssh root@server_ip_address2. Create a new user accountCreate a new user account using the useradd command:useradd usernameReplace username with the user name that you want to create.3. Set the user passwordRun the passwd command to set a password for the new user:passwd usernameYou will be prompted to confirm the password. Make sure you use a strong password.Changing password for user username. New password: Retype new password: passwd: all authentication tokens updated successfully. 4. Add the new user to the sudo groupBy default on CentOS systems, members of the group wheel are granted with sudo access. Add the new user to the wheel group:usermod -aG wheel usernameHow to use SudoSwitch to the newly created user:su - usernameTo use sudo, simply prefix the command with sudo and space.sudo [COMMAND]For example, to list the contents of the /root directory you would use:sudo ls -l /rootThe first time you use sudo from this account, you will see the following banner message and you will be prompted to enter the password for the user account.We trust you have received the usual lecture from the local System Administrator. It usually boils down to these three things:    #1) Respect the privacy of others.    #2) Think before you type.    #3) With great power comes great responsibility. [sudo] password for username: ConclusionThat’s all. You have successfully created a sudo user on your CentOS system. You can now use this user to perform administrative tasks on your server.Feel free to leave a comment if you have any questions.

[linuxforallsite]

Crear y Eliminar usuarios en Slackware 14.2

Crear y Eliminar usuarios en Slackware 14.2

Buenas tardes, vuelvo con otro mini how to de como crear un usuario en la distribución más longeva de GNU/Linux, Slackware 14.2.

Comencemos! Aclaración: voy a crear dos usuarios “ice” y “linuxeros” para mostrar exactamente lo que sucede. 1 – Una vez logueados como root, vamos a crear el usuario con el siguiente comando:

# useradd -m -g users -G audio,video,storage,games,power,wheel -s /bin/bash…

[skynatstech-blog]

Apache Server Optimization

Apache HTTP Server is a free software which is fast and secure and runs over half of all web servers around the globe. By customizing the Apache configuration, you can improve Apache performance without adding additional hardware such as RAM, CPU, etc.

Keep Apache Updated

Even though security bugs are seldom found within the web server, apache update is important in order to take advantage of the latest security features available.  

Click here to server management company

Optimize Apache settings

In order to optimize web server performance, several apache settings can be tweaked.

MaxKeepAliveRequests: The maximum number of requests accepted per connection is set out in this directive. The higher this value, the better the server performance. The recommended value is 500.

KeepAlive: This directive helps to display a webpage with reduced load time. Creating many connections may reduce the loading time but it also utilizes the resources on the server. Enabling keep-Alive directive helps to overcome this issue. Transfer all those files through a single connection rather than repeatedly opening and closing a new connection.

KeepAliveTimeout: The amount of time apache will wait before closing the connection for the subsequent request. Setting keepAliveTimeout to a high value can cause high load server performance problems.

Disable Unnecessary Modules

To extend the functionality and security of Apache you can add an unlimited number of modules. There are numerous Apache modules by default which are actually not needed. You could divert the modules to elsewhere, which makes the loading time longer and occupy dedicated server resources. To make our server less susceptible to threats it is important to disable the unnecessary modules. Mod_imap, mod_include, mod_info, mod_userdir, mod_autoindex are some of the modules that are usually not needed.

Run apache as separate user and group

With the default installation, Apache runs its process with user nobody or daemon. Create Apache User and Group and make an entry in apache configuration file, so as to tell Apache to run with this new user and restart the service.

groupadd apache useradd -d /var/www/ -g apache -s /bin/nologin apache

Configure MULTI-PROCESSING Module

One of the reasons for Apache’s slow performance may be its inability to handle the load. A multi – processing module will be helpful in such cases. MPM prefork module is part of CentOS 7 and is enabled by default. If mod deflate is enabled, MPM prefork module (shared) will be displayed for better performance. You can set this in the httpd.conf file.

You can add the following lines in the file considering the CPU and RAM allocated for the server.

<IfModule prefork.c>    StartServers 5    MinSpareServers 5    MaxSpareServers 10    MaxClients 150    MaxRequestsPerChild 3000 </IfModule>

StartServers: This sets the number of child server processes created at startup. This can initially be kept as a small number and increases gradually on a high payload server. This helps ensure the correct use of server resources.

MinSpareServers: This sets the minimum number of idle child server processes and can be configured for high payload servers.

MaxSpareServers: This sets the maximum number of idle child server processes. If this value is exceeded by the number of idle child server processes, the idle processes are killed

MaxClients: This is the maximum number of requests that Apache can handle simultaneously. The connection will be queued once this limit is reached.

MaxRequestsPerChild: This shows how many requests a child process handles before it ends. The child process will die once this limit has been reached. If the value is set to 0, the process will never die.

DNS Lookups

The main reason for slowing down the Apache web server is the time it takes to perform DNS lookups. In its access.log file, Apache records the full host name of each incoming client connection. Resolving each one takes a long time. The HostnameLookups option allows the DNS lookup to log hostnames instead of the IP address. HostnameLookups is Off by default in Apache.

For more info visit here: digitalocean server management

You can verify this by editing the configuration file of Apache. Make sure that the line HostnameLookups reads:

HostnameLookups Off

When you’re done, save and close the file and restart Apache to reflect changes.

Use Allow and Deny to Restrict access to Directories

We can restrict access to directories in the httpd.conf file with the options “Allow” and “Deny.” In this example, we will secure the root directory by setting the following in the httpd.conf file.

</Directory>    Options None    Order deny,allow    Deny from all   </Directory>

Options None: This option prevents users from enabling any optional features.

Order deny, allow: This is the order in which the directives “Deny” and “Allow” are handled. Here it will first “deny” and then “allow.”

Deny from all: This denies everyone’s request to the root directory, no one can access the root directory.

Tweak MySQL and PHP settings

Web servers seldom work alone. In most cases, a database server such as MySQL and scripting language support such as PHP to accompany the Apache web server. We have realized why optimizing the database server is equally important to avoid bottlenecks in it, which can slow down the web server. We also improve the performance of PHP pages using a caching or accelerator mechanism such as Zend OPcache.

MySQL is further tweaked by options such as table fragmentation and configuration settings – maximum connections, buffer size, size of the query cache, pool size, etc.

Conclusion

It is very easy to configure Apache for maximum performance. You can experiment with different options and measure the performance of the web server using various tools. We at Skynats have large experience in apache server optimization and you can contact us via Live Chat to know more details.

[arpithaappu-blog]

How to configure a user in vsftpd on a server?

Using cloud server for your business is cost-effective and you also get the increased quality of service best in class features. So today, for this reason, a lot of business are using the Linux cloud hosting for their website. And one fo the best advantages of using cloud server is that you can access to your business files and data from any place at any time via internet connection. So by having all these facilities, you can  hosting plans [concentrate on your core business. Not only that by having all these advantages it makes your Linux cloud hosting more reliable and flexible to use.

But today if you are already using Linux cloud server for your website and now if you are looking for information on how to configure a  user in vsftpd on a cloud server then here is the complete information on it.

Follow the below steps to configure a user in vsftpd on a cloud server:

>>> Add a system user

The very first thing that you need to do is to create a new user for FTP access in your vsftpd by creating a new valid Linux system user, to create use the below command

useradd test

passwd test

>>> Disable SSH access for FTP users

So when you create a default user creation script gives a user the /bin/bash shell, which is too powerful.And if you don’t want your users to log in to your server via SSH, you can block this access. Not only that when you change the shell to /bin/false, the users can log in only via FTP or mail if you have that setup. So you need to modify the user access by using this command

usermod -s /sbin/nologin test

>>> Chroot a user

Once after disabling the SSH access for FTP users now you can configure vsftpd to chroot users to their home directories for better security and privacy. And when you chroot users they can’t move up a level in the directory structure after they log in. So with the help of vsftpd you can chroot a user by editing the following in the file /etc/vsftpd/vsftpd.conf:

chroot_local_user=YES

chroot_list_enable=YES

chroot_list_file=/etc/vsftpd/vsftpd.chroot_list

>> Now you have to create a vsftp.chroot_list file and in there you need to enter users who do not use chroot.

Note: Every user uses chroot by default. Hence you need to, create a chroot_list file, even if the file is going to remain empty use the below command

touch /etc/vsftpd/vsftpd.chroot_list

 >> So once after the file is created and after you set up your  chroot_list you need to restart vsftpd so use the below command

[dotnettricks]

Top Asp. Net interview questions for experienced.

To develop into. You must enroll in MVC training if you are a Net MVC expert developer to study C#, a widely used programming language, OOPS, SQL Server, and several front-end technologies like HTML, JavaScript, and JQuery. Refer to the MVC interview question and answer pdf in addition to your studies to ace your job interview and advance your professional development. You will get all your concepts cleared if you opt for MVC tutorial.

MVC, or model-view-controller, is an acronym. It is a pattern for software design that was first used in the 1970s. Additionally, the MVC style enforces a separation of responsibilities, which separates the user interface from the domain model and controller functionality (view). These are some of the top asp.net MVC interview questions for experienced.

Here is a list of Asp. Net interview questions which can let you upskill your Career.

1. Describe the life cycle of an MVC application?

Any web application’s two main execution steps are as follows:

● Recognizing the desire

● Delivering a suitable reaction.

There are two primary phases in an MVC application life cycle:

● The request object is being created.

● Response to the browser is sent.

2. What do you think MVC filters mean?

Action methods in MVC are mutually exclusive and determined by controllers and UI controls. Example: The UserController class has the UserAdd and UserDelete functions. However, we frequently wish to do something before or after a particular operation. Using the ASP.NET MVC feature, pre- and post-action behaviors can be added to the controller’s action methods.

3. What does the controller’s before render() function do?

When we manually call render() before the conclusion of a particular operation, this function is necessary. Before the view is rendered and after the logic for the controller action, this method is invoked. It is hardly frequently used.

4. Define DispatcherServerlet?

A class called DispatcherServerlet is responsible for receiving incoming requests and assigning them to the most appropriate resources, such as Views, Models, and Controllers.

5. What in MVC is attribute-based routing?

In ASP.NET MVC, a new attribute route has been added. The routing element can be used to determine URL structure. If the route property is used to decorate the GotoAbout action, indicates that GotoAbout can be called using the Users/about URL structure.

6. How does the MVC pattern handle routing?

Registered routes in the program comprise the route collection, or group, of routes. The collection routes are recorded through the RegisterRoutes method. If the request meets the pattern, the route and a handler define the URL pattern. The first parameter of the MapRoute is the name of the route; the second is the pattern that the URL matches; and the third is the default values for the Placeholders.

7. What distinguishes ViewResult from ActionResult?

ActionResult is an abstract class, and ViewResult is inherited from AbstractResult. When you are dynamically deriving various types of views, ActionResult is useful. FileStreamResult, ViewResult, and JsonResult are ActionResult’s descendant classes. This is a common asp.net MVC interview question for experienced.

8. Describe NonActionAttribute’s significance?

If we want to stop a public method of a controller from being used as an action method by default, we can do so by giving it the NonActionattribute.

9. Define the partial view in MVC?

The MVC partial view renders a portion of the view content. This lessens the need for code requests. The partial view enables the display of a view inside the parent view.

10. Describe MVC Scaffolding?

For ASP.NET web apps, MVC Scaffolding is a framework for code creation. When we want to quickly add code that communicates with data activities in our project, we use scaffolding. Field page templates, filter templates, and entity page templates are included. These scaffold templates make it possible to construct a working data-driven website quickly.

11. Explain ORM and its application?

A framework called the ORM (object-relational mapping) aids in minimizing the amount of handwritten code in a web application. When there aren’t any strict performance requirements, ORM is employed; nevertheless, high-load applications might use frameworks like Dapper.

12. Describe the POST and GET action types?

A resource provided by the POST action type receives data to process. With every POST request, we include the crucial URL and data. Overloads may be Absorbed.

A resource provided by the GET action type is asked for data. With each GET request, the required URLs are passed. Overloads may be absorbed.

13. How will MVC validation be implemented?

With the aid of validators established in the System, we can implement validation in the MVC application.ComponentModel. Namespace for DataAnnotations. The many validators include StringLength, Required, Range, and DataType.

14. What exactly do you mean by WebAPI?

Using WebAPI technology, you may use RESTful principles to provide data over HTTP. This method was implemented to satisfy many clients who needed to consume data from Windows, JavaScript, mobile devices, and other sources.

15. Give us an example of when employing an IoC container was

Advantageous?

The advantages include external management of every object’s life, future contract implementation changes, dependency list changes that do not affect things utilizing the service, and sharing one instance by numerous unrelated Customers.

16. What is Spring MVC?

A Java framework called Spring MVC creates web applications by using the MVC design pattern. It carries out all of the fundamental components of the spring framework, including dependency injection and inversion of control. Spring MVC offers a classy method for using MVC in the Spring Framework with DispatcherServlet. This class translates incoming requests to view models and controllers after receiving them.

17. What does MVC’s ViewState term mean to you?

ViewState is the basis for one of the most typical asp.net interview questions. In contrast to WebForms, MVC lacks ViewState. This is because ViewState is saved in a hidden field on the page, considerably increasing its size and slowing down page loading.

Conclusion

This was a detailed list of MVC-specific ASP.NET interview questions. Be prompt and assured when answering questions during an interview. Answers should be brief and unambiguous, without discussion.

[computingpostcom]

How To Install Prometheus on Debian 11| Debian 10 Linux?. Prometheus is a free and open source monitoring system that enables you to collect time-series data metrics from any target systems. Its web interface enables you to perform powerful queries, visualize collected data, and to configure alerts. In this guide, we will cover the installation of Prometheus and node_exporter on Debian 11 / Debian 10. Since this is a binary installation method, there is no required dependency to continue with the setup. Step 1: Create Prometheus system user / group We’ll create a dedicated Prometheus system user and group. The  -r or –system option is used for this purpose. sudo groupadd --system prometheus sudo useradd -s /sbin/nologin --system -g prometheus prometheus This creates a system user which doesn’t need /bin/bash shell, that’s why we used -s /sbin/nologin. Step 2: Create configuration and data directories Prometheus needs directories to store data and configuration files. Create all required directories using the commands below. sudo mkdir /var/lib/prometheus for i in rules rules.d files_sd; do sudo mkdir -p /etc/prometheus/$i; done Step 3: Download and Install Prometheus on Debian 11 / Debian 10 Let’s download the latest release of Prometheus archive and extract it to get binary files. You can check releases from Prometheus releases Github page. sudo apt-get update sudo apt-get -y install wget curl mkdir -p /tmp/prometheus && cd /tmp/prometheus curl -s https://api.github.com/repos/prometheus/prometheus/releases/latest|grep browser_download_url|grep linux-amd64|cut -d '"' -f 4|wget -qi - Extract the file. tar xvf prometheus*.tar.gz cd prometheus*/ Move the prometheus binary files to /usr/local/bin/ Since /usr/local/bin/ is in your PATH, let’s copy binary files to it. sudo mv prometheus promtool /usr/local/bin/ Move prometheus configuration template to /etc directory. sudo mv prometheus.yml /etc/prometheus/prometheus.yml Also move consoles and console_libraries to /etc/prometheus directory: sudo mv consoles/ console_libraries/ /etc/prometheus/ cd ~/ rm -rf /tmp/prometheus Step 4: Create/Edit a Prometheus configuration file. Prometheus configuration file will be located under /etc/prometheus/prometheus.yml. cat /etc/prometheus/prometheus.yml The default configuration file looks similar to below. # my global config global: scrape_interval: 15s # Set the scrape interval to every 15 seconds. Default is every 1 minute. evaluation_interval: 15s # Evaluate rules every 15 seconds. The default is every 1 minute. # scrape_timeout is set to the global default (10s). # Alertmanager configuration alerting: alertmanagers: - static_configs: - targets: # - alertmanager:9093 # Load rules once and periodically evaluate them according to the global 'evaluation_interval'. rule_files: # - "first_rules.yml" # - "second_rules.yml" # A scrape configuration containing exactly one endpoint to scrape: # Here it's Prometheus itself. scrape_configs: # The job name is added as a label `job=` to any timeseries scraped from this config. - job_name: 'prometheus' # metrics_path defaults to '/metrics' # scheme defaults to 'http'. static_configs: - targets: ['localhost:9090'] Step 5: Create a Prometheus systemd Service unit file To be able to manage Prometheus service with systemd, you need to explicitly define this unit file. sudo tee /etc/systemd/system/prometheus.service Aug 31 19:14:07 debian-bullseye-01 prometheus[1890]: level=info ts=2021-08-31T19:14:07.190Z caller=main.go:839 fs_type=EXT4_SUPER_MAGIC Aug 31 19:14:07 debian-bullseye-01 prometheus[1890]: level=info ts=2021-08-31T19:14:07.190Z caller=main.go:842 msg="TSDB started" Aug 31 19:14:07 debian-bullseye-01 prometheus[1890]: level=info ts=2021-08-31T19:14:07.191Z caller=main.go:969 msg="Loading configuration file" filename=/etc/prometheus/prometheus.yml Aug 31 19:14:07 debian-bullseye-01 prometheus[1890]: level=info ts=2021-08-31T19:14:07.

192Z caller=main.go:1006 msg="Completed loading of configuration file" filename=/etc/prometheus/prometheus.yml> Aug 31 19:14:07 debian-bullseye-01 prometheus[1890]: level=info ts=2021-08-31T19:14:07.192Z caller=main.go:784 msg="Server is ready to receive web requests." Access Prometheus web interface on URL http://[ip_hostname]:9090. Step 6: Install node_exporter onDebian 11 / Debian 10 Download node_exporter archive. curl -s https://api.github.com/repos/prometheus/node_exporter/releases/latest| grep browser_download_url|grep linux-amd64|cut -d '"' -f 4|wget -qi - Extract downloaded file and move the binary file to /usr/local/bin. tar -xvf node_exporter*.tar.gz cd node_exporter*/ sudo cp node_exporter /usr/local/bin Confirm installation. $ node_exporter --version node_exporter, version 1.3.0 (branch: HEAD, revision: c65f870ef90a4088210af0319498b832360c3366) build user: root@4801f8f250a6 build date: 20211118-16:34:14 go version: go1.17.3 platform: linux/amd64 Create node_exporter service. sudo tee /etc/systemd/system/node_exporter.service

[connect-kreations]

Top 50 Linux Commands You Must Know as a Regular User...

1. ls - view contents of directory (list)

2. pwd - path of the current directory

3. cd - change directoryn

4. mkdir - make new directory

5. mv - move files / rename files

6. cp - copy files

7. rm - remove files

8. touch - create blank new file

9. rmdir - delete directory

10. cat - list content of file to terminal

11. clear - clear terminal window

12. echo - move data into a file

13. less - Read text file one screen at a time

14. man - show manual of Linux commands

15. sudo - enables you to perform tasks that require administrative or root permissions

16. top - task manager in terminal

17. tar - used to archive multiple files into a tarball

18. grep - used to searching words in specific files

19. head - view first lines of any text file

20. tail - view last lines of any text file

21. diff - compares the contents of two files line by line

22. kill - used for killing unresponsive program

23. jobs - display all current jobs along with their statuses

24. sort - is a command line utility for sorting lines of text files

25. df - info about system disk

26. du - check how much space a file or directory takes

27. zip - to compress your files into a zip archive

28. unzip - to extract the zipped files from a zip archive

29. ssh - a secure encrypted connection between two hosts over and insecure network

30. cal - shows calendar

31. apt - command line tool for interaction with packaging system

32. alias - custom shortcuts used to represent a command

33. w - current user info

34. whereis - used to locate the binary, source, manual page files

35. whatis - used to get one-line man page description

36. useradd - used to create a new user

37. passwd - used to changing password of current user

38. whoami - print current user

39. uptime - print current time when machine starts

40. free - print free disk space info

41. history - print used commands history

42. uname - print detailed information about your Linux system

43. ping - to check connectivity status to a server

44. chmod - to change permissions of files and directories

45. chown - to change ownership of files and directories

46. find - using find searches for files and directories

47. locate - used to locate a file, just like the search command in Windows

48. ifconfig - print ip address stuff

49. ip a - similar to ifconfig but shortest print

50. finger - gives you a short dump of info about a user