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    <title>Forem: Kasim Hussain</title>
    <description>The latest articles on Forem by Kasim Hussain (@kasim_hussain_5f389fb5097).</description>
    <link>https://forem.com/kasim_hussain_5f389fb5097</link>
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      <title>Forem: Kasim Hussain</title>
      <link>https://forem.com/kasim_hussain_5f389fb5097</link>
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    <item>
      <title>🖥️ Advanced Linux Commands</title>
      <dc:creator>Kasim Hussain</dc:creator>
      <pubDate>Sat, 10 Jan 2026 10:05:18 +0000</pubDate>
      <link>https://forem.com/kasim_hussain_5f389fb5097/advanced-linux-commands-2ni3</link>
      <guid>https://forem.com/kasim_hussain_5f389fb5097/advanced-linux-commands-2ni3</guid>
      <description>&lt;p&gt;Advanced Linux commands for System Management&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;🔐 Advanced File Permissions &amp;amp; Ownership
File Permissions in Linux:&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;r: Read (4) 📖&lt;/p&gt;

&lt;p&gt;w: Write (2) ✍️&lt;/p&gt;

&lt;p&gt;x: Execute (1) ▶️&lt;/p&gt;

&lt;p&gt;Permissions are added together to set them.&lt;/p&gt;

&lt;p&gt;🔧 Modify File Permissions (chmod)&lt;br&gt;
✅ Give full permission to the owner, read-execute to others:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;chmod 755 script.sh
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;7 → Owner permission: Read (4) + Write (2) + Execute (1) = 7&lt;/p&gt;

&lt;p&gt;5 → Group permission: Read (4) + Execute (1) = 5&lt;/p&gt;

&lt;p&gt;5 → Others permission: Read (4) + Execute (1) = 5&lt;/p&gt;

&lt;p&gt;❌ Make a file read-only for everyone:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;chmod 444 important.txt
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;🔒 No one can modify the file because Write (2) is removed.&lt;br&gt;
🚫 Remove execute permission from a file:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;chmod -x file.sh
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;The -x removes execute permission from the file.&lt;br&gt;
👤 Change File Ownership (chown &amp;amp; chgrp)&lt;br&gt;
👤 Change the file owner:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;sudo chown newuser file.txt
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;newuser becomes the owner of file.txt.&lt;br&gt;
👥 Change both owner and group:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;sudo chown newuser:newgroup file.txt
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;newuser is the new owner.&lt;/p&gt;

&lt;p&gt;newgroup is the new group.&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;🌐 Network Monitoring &amp;amp; Troubleshooting
🔍 Check Open Network Connections (netstat, ss)
📶 List all open ports and services:&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;netstat -tulnp
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;t: Shows TCP connections.&lt;/p&gt;

&lt;p&gt;u: Shows UDP connections.&lt;/p&gt;

&lt;p&gt;l: Shows listening ports.&lt;/p&gt;

&lt;p&gt;n: Displays numeric addresses.&lt;/p&gt;

&lt;p&gt;p: Shows process ID (PID).&lt;/p&gt;

&lt;p&gt;🌍 Check listening ports (alternative to netstat):&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;ss -tulnp
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;⚡ Faster alternative to netstat.&lt;br&gt;
🛠️ Network Diagnostics (ping, nslookup, traceroute)&lt;br&gt;
🔄 Test network connectivity:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;ping google.com
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Sends ICMP echo requests to check if google.com is reachable.&lt;br&gt;
🌐 Get DNS information of a domain:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;nslookup google.com
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Resolves the IP address of google.com using DNS lookup.&lt;br&gt;
🏃 Trace the route packets take to a destination:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;traceroute google.com
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Shows each hop (router) a packet takes to reach google.com.&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;💽 Transfer Files Over SSH (scp)
📂 Copy a file to a remote server:&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;scp file.txt user@remote:/path/
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Securely copies file.txt from your local machine to /path/ on the remote server.&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;🔑 SSH Command for Remote Access
🚀 Access a remote server using SSH:&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;ssh user@remote
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;ssh: Securely logs you into a remote server.&lt;/p&gt;

&lt;p&gt;user: Replace with the username on the remote server.&lt;/p&gt;

&lt;p&gt;remote: Replace with the server's IP address or hostname (e.g., 192.168.1.10).&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;⏳ Automation &amp;amp; Scheduling Tasks (cron)
⌚ Schedule Jobs with Cron
📝 Edit the cron table:&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;crontab -e
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Opens the cron job editor.&lt;br&gt;
💾 Schedule a backup every day at midnight:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;0 * * * * /home/user/backup.sh
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;This cron job will run /home/user/backup.sh at the start of every hour.&lt;/p&gt;

</description>
    </item>
    <item>
      <title>LINUX FOR DEVOPS.....</title>
      <dc:creator>Kasim Hussain</dc:creator>
      <pubDate>Mon, 05 Jan 2026 12:28:18 +0000</pubDate>
      <link>https://forem.com/kasim_hussain_5f389fb5097/linux-for-devops-58m5</link>
      <guid>https://forem.com/kasim_hussain_5f389fb5097/linux-for-devops-58m5</guid>
      <description>&lt;p&gt;Linux Founder&lt;br&gt;
Linus Benedict Torvalds is a Finnish software engineer best known for having initiated the development of the Linux kernel and git revision control system.&lt;/p&gt;

&lt;p&gt;History of Linux&lt;br&gt;
Linus Torvalds a student at the University of Helsinki, Finland, USA developed the first code of Linux i.e. Linux 0.01, which became so popular that people encourages him to develop the new code of Linux. On 5 September 1991 Linus Torvalds developed the first official version of Linux i.e. Linux 0.02.&lt;/p&gt;

&lt;p&gt;Linux File System Hierarchy&lt;/p&gt;

&lt;p&gt;Linux is an open-source operating system. Linux follows the File System Hierarchy in which everything is represented as a file i.e. stored in a directory. Linux has a single-rooted, inverted tree-like structure. The root directory in Linux is represented as "/" (forward slash) also called the top-level directory.&lt;/p&gt;

&lt;p&gt;Top-level directory -&amp;gt; "/"&lt;/p&gt;

&lt;p&gt;The base of the Linux directory is the root. This is the starting point of FSH. Every directory arises from the root directory. It is represented by a forward slash (/).&lt;/p&gt;

&lt;p&gt;If someone says to look into the slash directory, they refer to the root directory.&lt;/p&gt;

&lt;p&gt;/root&lt;/p&gt;

&lt;p&gt;It is the home directory for the root user (superuser).&lt;br&gt;
/bin -&amp;gt; User Binaries&lt;/p&gt;

&lt;p&gt;Contains binary executable.&lt;/p&gt;

&lt;p&gt;Common Linux commands you need to use in single-user modes are located under this directory.&lt;/p&gt;

&lt;p&gt;Commands used by all the users of the system are located here.&lt;/p&gt;

&lt;p&gt;/sbin -&amp;gt; System Binaries&lt;/p&gt;

&lt;p&gt;Just like /bin, /sbin also contains binary executables.&lt;/p&gt;

&lt;p&gt;But, the Linux commands located under this directory are used typically by the system administrators, for system maintenance purposes.&lt;/p&gt;

&lt;p&gt;For example, iptables, reboot, fdisk, ifconfig, and swapon.&lt;/p&gt;

&lt;p&gt;/dev -&amp;gt; Device Files&lt;/p&gt;

&lt;p&gt;contains hardware device files.&lt;/p&gt;

&lt;p&gt;Contains device files.&lt;/p&gt;

&lt;p&gt;These include terminal devices, USB, or any device attached to the system.&lt;/p&gt;

&lt;p&gt;For example: /dev/tty1, /dev/usbmon0.&lt;/p&gt;

&lt;p&gt;/var -&amp;gt; Variable Files&lt;/p&gt;

&lt;p&gt;The variable data files such as log files are located in the /var directory.&lt;/p&gt;

&lt;p&gt;File contents that tend to grow are located in this directory. This includes:-&lt;/p&gt;

&lt;p&gt;/var/log: System log files generated by OS and other applications.&lt;/p&gt;

&lt;p&gt;/var/lib: Contains database and packages files.&lt;/p&gt;

&lt;p&gt;/var/mail: Contains Emails.&lt;/p&gt;

&lt;p&gt;/var/tmp: Contains temporary files needed for reboot.&lt;/p&gt;

&lt;p&gt;/mnt -&amp;gt; Mount Directory&lt;/p&gt;

&lt;p&gt;This directory is used to mount a file system temporarily.&lt;br&gt;
/media -&amp;gt; Removable Media Devices&lt;/p&gt;

&lt;p&gt;The /media directory contains subdirectories where removable media devices inserted into the computer are mounted.&lt;br&gt;
/usr -&amp;gt; User Binaries&lt;/p&gt;

&lt;p&gt;The /usr directory contains applications and files used by users, as opposed to applications and files used by the system.&lt;br&gt;
/etc -&amp;gt; Configuration files&lt;/p&gt;

&lt;p&gt;It contains all configuration files of the server.&lt;/p&gt;

&lt;p&gt;The core configuration files are stored in the /etc directory. It controls the behavior of an operating system or application. This directory also contains startup and shutdown program scripts that are used to start or stop individual programs.&lt;/p&gt;

&lt;p&gt;/boot -&amp;gt; Boot Loader Files&lt;/p&gt;

&lt;p&gt;The /boot directory contains the files needed to boot the system.&lt;/p&gt;

&lt;p&gt;For example, the GRUB bootloader's files and your Linux kernels are stored here.&lt;/p&gt;

&lt;p&gt;/opt -&amp;gt; Optional Applications&lt;/p&gt;

&lt;p&gt;The opt directory is used for installing the application software from third-party vendors that are not available in the Linux distribution. Usually, the software code is stored in the opt directory and the binary code is linked to the bin directory so that all users can run that software.&lt;br&gt;
/home -&amp;gt; Home Directory&lt;/p&gt;

&lt;p&gt;It contains the secondary user's home directory.&lt;br&gt;
/tmp -&amp;gt; Temporary Files&lt;/p&gt;

&lt;p&gt;A directory that contains temporary files created by the system and users.&lt;/p&gt;

&lt;p&gt;Files under this directory are deleted when the system is rebooted.&lt;/p&gt;

&lt;p&gt;Linux Architecture&lt;br&gt;
In the Linux architecture, the two most important components are the shell and Kernel. The kernel is the one that gives commands to the hardware to perform necessary actions. On the other hand, the shell is used to access the kernel.&lt;/p&gt;

&lt;p&gt;In simple words, the shell is used to communicate with the kernel using Linux commands, and based on these commands the kernel further orders the hardware to do so. Shell is used to get the kernel and the kernel is used to get the hardware.&lt;/p&gt;

&lt;p&gt;Hardware includes several peripheral devices such as a CPU, HDD, and RAM.&lt;/p&gt;

&lt;p&gt;Basic Commands&lt;br&gt;
pwd -&amp;gt; It shows the present working directory.&lt;/p&gt;

&lt;p&gt;Is -&amp;gt; It shows the available files and directory list in the current working directory.&lt;/p&gt;

&lt;p&gt;uname -&amp;gt; It shows the name of the kernel (OS).&lt;/p&gt;

&lt;p&gt;uname -r -&amp;gt; It shows the version of the kernel.&lt;/p&gt;

&lt;p&gt;cd -&amp;gt; It is used to change the directory.&lt;/p&gt;

&lt;p&gt;clear -&amp;gt; It is used for clearing the screen.&lt;/p&gt;

&lt;p&gt;whoami -&amp;gt; It shows the current login user name.&lt;/p&gt;

&lt;p&gt;history -&amp;gt; It shows a list of previously used commands.&lt;/p&gt;

&lt;p&gt;date -&amp;gt; It shows the time and date.&lt;/p&gt;

&lt;p&gt;Create a directory&lt;br&gt;
To create a single directory.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;mkdir dir_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To create multiple directories.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;mkdir dir_name1 dir_name2 dir_name3
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To create a directory path (directory inside the directory).&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;mkdir -p dir1/dir2/dir3/dir4
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To create directories with serial-wise numbers.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;mkdir dir{1..10}
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Create a file&lt;br&gt;
To create a file.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;touch file
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To create multiple files.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;touch file1 file2 file3
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To create files with serial-wise numbers.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;touch file{1..10}
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;For copy &amp;amp; paste&lt;br&gt;
To copy and paste files or directories.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;cp &amp;lt;option&amp;gt; &amp;lt;source&amp;gt; &amp;lt;destination&amp;gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Options :&lt;/p&gt;

&lt;p&gt;-r or recursive&lt;/p&gt;

&lt;p&gt;-v for verbose&lt;/p&gt;

&lt;p&gt;-f for forcefully&lt;/p&gt;

&lt;p&gt;For removing files and directory&lt;br&gt;
For deleting files or directories.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;rm -rvf file_name
rm -rvf dir_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;For moving or renaming files &amp;amp; directory&lt;br&gt;
To rename a file or directory.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;mv old_name new_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To move a file, directory to another directory.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;mv source_file destination
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;User Management&lt;br&gt;
For creating a user account.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;useradd user_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;For checking user account properties.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;cat /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;For creating a user account password.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;passwd user_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;For checking user password properties.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep user_name/etc/shadow
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;For switching user accounts.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;su user_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To log out from a user account.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;exit
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Or press Ctrl + D key.&lt;/p&gt;

&lt;p&gt;For Deleting a user account.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;userdel user_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To change the user Login name.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;usermod -l login_name old_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Group Management&lt;br&gt;
In Linux, groups are collections of users. Creating and managing groups is one of the simplest ways to deal with multiple users simultaneously, especially when dealing with permissions. The /etc/group file stores group information and is the default configuration file.&lt;/p&gt;

&lt;p&gt;To add a group account.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;groupadd group_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To check group account property.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;cat /etc/group
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;For checking group admin property.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;cat /etc/gshadow
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To delete a group.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;groupdel group_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To add a single member to a group.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;gpasswd -a user_name group_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To add multiple members to a group.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;gpasswd -M user_name1,user_name2,user_name3 group_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To remove a group member.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;gpasswd -d user_name group_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To make a group admin.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;gpasswd -A user_name group_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Linux File System Permission&lt;br&gt;
Type of File Permission&lt;/p&gt;

&lt;p&gt;Basic Permission.&lt;/p&gt;

&lt;p&gt;Special Permission.&lt;/p&gt;

&lt;p&gt;Access Control List (ACL) Permission.&lt;/p&gt;

&lt;p&gt;For checking file permission&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;ls -l file_name&lt;/p&gt;

&lt;p&gt;For checking directory permissions&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;ls -ld dir_name&lt;/p&gt;

&lt;p&gt;Permission in detail&lt;/p&gt;

&lt;p&gt;There are 3 types of permission classes:-&lt;/p&gt;

&lt;p&gt;User&lt;/p&gt;

&lt;p&gt;Group&lt;/p&gt;

&lt;p&gt;Other&lt;/p&gt;

&lt;p&gt;Permission classes tell us about the permissions that users, group members, and other users have over that file/directory.&lt;/p&gt;

&lt;p&gt;File type tells the type of file for eg. "d" stands for directory and "-" stands for file.&lt;/p&gt;

&lt;p&gt;"r" stands for Read.&lt;/p&gt;

&lt;p&gt;"w" stands for Write.&lt;/p&gt;

&lt;p&gt;"x" stands for Execute.&lt;/p&gt;

&lt;p&gt;Permission Set&lt;/p&gt;

&lt;p&gt;Permission with numeric &amp;amp; symbol&lt;/p&gt;

&lt;p&gt;For changing permissions&lt;/p&gt;

&lt;p&gt;To add read permissions to the owner.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;chmod u+r file_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To add read-write permissions to the group.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;chmod g+rw file_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To remove read permission for others.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;chmod o-r file_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;For changing ownership&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;chown user_name file_name&lt;br&gt;
chown user_name directory_name&lt;/p&gt;

&lt;p&gt;For changing group ownership&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;chgrp group_name file_name&lt;br&gt;
chgrp group_name directory_name&lt;/p&gt;

&lt;p&gt;Set permissions with numeric values&lt;/p&gt;

&lt;p&gt;r (read) = 4&lt;br&gt;
w (write) = 2&lt;br&gt;
x (execute) = 1&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;chmod 751 file_name&lt;/p&gt;

&lt;p&gt;Access Control List (ACL)&lt;br&gt;
Access control list (ACL) provides an additional, more flexible permission mechanism for file systems.&lt;/p&gt;

&lt;p&gt;Access Control List is a service that provides special permission to specific users and groups for particular directories and files.&lt;/p&gt;

&lt;p&gt;Use of ACL&lt;/p&gt;

&lt;p&gt;Think of a scenario in which a particular user is not a member of the group created by you but still, wants to give some read or write access, how can you do it without making the user a member of the group, here comes in picture Access Control List, ACL helps us to do this trick.&lt;/p&gt;

&lt;p&gt;For checking ACL permissions.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;getfacl file_name
getfacl dir_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To set ACL permissions for the user.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;setfacl -m user::rwx file_name
setfacl -m user::rwx dir_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To remove the ACL permissions for the user.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;setfacl -x user:user_name file_name
setfacl -x user:user_name dir_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To set ACL permissions for the group.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;setfacl -m group::rwx file_name
setfacl -m group::rwx dir_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To remove ACL permissions for the group.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;setfacl -x group file_name
setfacl -x group dir_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To remove all the ACL permissions.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;setfacl -b file_name
setfacl -b dir_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Regular Expressions&lt;br&gt;
Regular expressions are special characters that help search data, matching complex patterns.&lt;/p&gt;

&lt;p&gt;GREP (Global Regular Expression Print)&lt;/p&gt;

&lt;p&gt;The grep filter searches a file for a particular pattern of characters and displays all the lines that contain that pattern.&lt;/p&gt;

&lt;p&gt;Search a word (string in a file).&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep root /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Search a string in multiple files.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep root /etc/passwd /etc/group
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Search a string insensitively in a file.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep -i RooT /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Search a string in all files recursively.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep -r root /
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Inverting the string match.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep -v root /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Display the total lines of the string matched.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep -c root /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Display the file names that match the string.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep -l root /etc/passwd /etc/shadow
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Display the file names that do not contain the string.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep -L root /etc/passwd /etc/shadow
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Displaying the string match line with a number.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep -n root /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Display the lines that start with a string.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep ^root /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Display the lines that end with a string.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep /bin/bash$ /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Search and redirect output in a new file.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;grep root /etc/passwd &amp;gt; /home/ubuntu/grep.txt
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Find&lt;br&gt;
The Linux Find Command is one of the most important and much-used commands in the Linux system. The find command is used to search and locate the list of files and directories based on conditions you specify for files that match the arguments. Find can be used in a variety of conditions you can find files by permissions, users, groups, file type, date, size, and other possible criteria.&lt;/p&gt;

&lt;p&gt;Find files under /home directory.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;find /home -name file_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Find files with suid permission.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;find / -perm 4755
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Find files with guid permission.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;find / -perm 2644
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Find files with sticky bit permission.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;find / -perm 1755
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Find command based on user.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;find / -user root
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Find commands based on the group.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;find / -group group_name
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Search the file with less than IOMB in a folder.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;find /tmp -size -10M
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Search the file with more than IOMB in a folder.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;find /tmp -size +10M
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;WC (Word Count)&lt;br&gt;
The wc command is used for counting words and line numbers.&lt;/p&gt;

&lt;p&gt;Count the number of lines.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;wc -l /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Count the number of words.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;c -w /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Head&lt;br&gt;
Head command is used to display the top lines of a file.&lt;/p&gt;

&lt;p&gt;Display the top 10 lines of a file.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;head /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Display top specific no line of the file.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;head -n 15 /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Tail&lt;br&gt;
The tail command is used to display the bottom lines of a file.&lt;/p&gt;

&lt;p&gt;Display the bottom 10 lines of the file.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tail /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Display the bottom specific lines of a file.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tail -n 5 /etc/passwd
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Archive File in Linux&lt;br&gt;
Archiving is a process of combining multiple files and directories (same or different sizes) into one file. The archive process is very useful for the backup and compression size of data in Linux.&lt;/p&gt;

&lt;p&gt;What is Tar?&lt;/p&gt;

&lt;p&gt;The Linux tar stands for tape archive, which is used by a large number of Linux/Unix system administrators to compress size or drive backup. To create an archive tar there're needed some compression algorithms such as gzip, bz2 and xz.&lt;/p&gt;

&lt;p&gt;Tar command syntax.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;tar  &lt;/p&gt;

&lt;p&gt;c - To create&lt;/p&gt;

&lt;p&gt;x - To extract&lt;/p&gt;

&lt;p&gt;v - To verbose&lt;/p&gt;

&lt;p&gt;f - To forcefully&lt;/p&gt;

&lt;p&gt;t - To test&lt;/p&gt;

&lt;p&gt;z - To gzip&lt;/p&gt;

&lt;p&gt;j - To bz2&lt;/p&gt;

&lt;p&gt;J - To xz&lt;/p&gt;

&lt;p&gt;C - To specific destination&lt;/p&gt;

&lt;p&gt;To create a tar archive file.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tar -cvf /mnt/backup.tar /var
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To show file size in a human-readable format.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;du -sh /var
du -sh /mnt/backup.tar
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To extract a tar archive file on the default location.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tar -xvf /mnt/backup.tar
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To extract a tar archive file on a specific location.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tar -xvf /mnt/backup.tar -C /root/Desktop/
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To create a tar archive file with compress in size (gzip).&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tar -cvzf /mnt/backup.tar.gz /var
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To extract a tar archive file with compress in size (gzip).&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tar -xvzf /mnt/backup.tar.gz
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To extract a tar archive file with compress in size (bzip2/bz2).&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tar -xvjf /mnt/backup.tar.bz2
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To create a tar archive file with compress in size (xz).&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tar -cvJf /mnt/backup.tar.xz /var
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To extract a tar archive file with compress in size (xz).&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tar -xvJf /mnt/backup.tar.xz
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Job Automation&lt;br&gt;
Job automation allows us to perform tasks automatically in OS by using tools.&lt;/p&gt;

&lt;p&gt;This feature is very useful for the administrator to assign the task to OS whenever he is not present or performs daily basis work.&lt;/p&gt;

&lt;p&gt;Two types of job automation&lt;/p&gt;

&lt;p&gt;at - at command is used to execute a job only one time.&lt;/p&gt;

&lt;p&gt;crontab - Crontab command is used to execute jobs multiple times.&lt;/p&gt;

&lt;p&gt;To set a job with at command.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;date
8:10 AM
at &amp;gt; useradd shub
at &amp;gt; 
#Ctrl+d (write &amp;amp; quit)
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To show pending at job.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;atq
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To remove at job.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;atrm 2
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To restrict a user from accessing at.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;vim /etc/at.deny
Shub (add here user name)
:wq #(write&amp;amp;quit)
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Cronjob:-&lt;/p&gt;

&lt;p&gt;To start a crond service.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;systemctl start crond
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To enable a crond service (Permanent on).&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;systemctl enable crond
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To set cron jobs.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;crontab -e
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To show the cronjobs of the current user.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;crontab -l
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To remove the cron jobs.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;crontab -r
#Or go to the crontab file and remove job line
crontab -e
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To set a cronjob to other users.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;crontab -u shub -e
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To show the cronjob, other users&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;crontab -u shub -l
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To restrict users from crond service.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;vim /etc/cron.deny
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;To check the crontab log file.&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;tail -f /var/log/cron
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;

&lt;p&gt;Sudo Command&lt;br&gt;
What is sudo?&lt;/p&gt;

&lt;p&gt;Sudo ("superuser do", or "switch user do") allows a user with proper permissions to execute a command as another user, such as the superuser.&lt;/p&gt;

&lt;p&gt;Sudo allows a permitted user to execute a command as another user, according to specifications in the /etc/sudoers file.&lt;/p&gt;

&lt;p&gt;Wheel group&lt;br&gt;
A wheel is a system group that by default has sudo privileges, if we add any member to that group then that user got sudo privileges.&lt;/p&gt;

&lt;p&gt;By default, all the members of the wheel group got sudo privileges.&lt;/p&gt;

&lt;p&gt;Introduction In DevOps, Linux mastery is an essential skill. From infrastructure automation to continuous deployment, Linux drives most contemporary development environments. This guide discusses the key Linux skills for DevOps professionals.&lt;/p&gt;

&lt;p&gt;Linux is an open-source operating system that is highly stable, secure, and flexible. Linux finds extensive applications in servers, desktops, and embedded systems. Linux has excellent performance, optimal resource utilization, and has a variety of distributions such as Ubuntu, Fedora, and CentOS. Its open-source model supports innovation and customization, and it is hence very popular among developers, IT specialists, and DevOps engineers&lt;/p&gt;

&lt;p&gt;Why Linux for DevOps?&lt;/p&gt;

&lt;p&gt;Open Source and Cost-Effective&lt;/p&gt;

&lt;p&gt;Stability and Performance&lt;/p&gt;

&lt;p&gt;Powerful Command Line Interface (CLI)&lt;/p&gt;

&lt;p&gt;Automation and Scripting&lt;/p&gt;

&lt;p&gt;Containerization and Orchestration Support&lt;/p&gt;

&lt;p&gt;Strong Security Features&lt;/p&gt;

&lt;p&gt;Cloud and Server Dominance&lt;/p&gt;

&lt;p&gt;Flexibility in Environment Management&lt;/p&gt;

&lt;p&gt;Wide Community Support&lt;/p&gt;

&lt;p&gt;Popular DevOps Tools are Native to Linux&lt;/p&gt;

&lt;p&gt;Advantages of Linux for DevOps:&lt;br&gt;
Open Source &amp;amp; Affordable: Linux is open-source and free, highly customizable for DevOps environments without any licensing fees.&lt;/p&gt;

&lt;p&gt;Strong Command Line Interface (CLI): The terminal in Linux provides strong utilities such as grep, awk, and sed, which simplify automation and scripting.&lt;/p&gt;

&lt;p&gt;Stability &amp;amp; Dependability: Linux is famous for its solid performance, particularly in server environments, with little downtime.&lt;/p&gt;

&lt;p&gt;Compatibility with DevOps Tools: Popular DevOps tools like Docker, Kubernetes, Jenkins, and Ansible are built to operate natively on Linux.&lt;/p&gt;

&lt;p&gt;Security Features: Linux supports robust security features such as file permissions, roles for users, and inbuilt firewall functionality.&lt;/p&gt;

&lt;p&gt;Automation Support: Linux offers shell scripting and support for automation tools, making automation of tasks easier.&lt;/p&gt;

&lt;p&gt;Containerization &amp;amp; Virtualization: Native container support (e.g., Docker) and support for lightweight virtualization in Linux is vital to DevOps workflow.&lt;/p&gt;

&lt;p&gt;Community Support: Linux has a large community of developers, providing comprehensive support for troubleshooting and enhancement.&lt;/p&gt;

&lt;p&gt;Effective Package Management: Utilizing tools such as apt, yum, and dnf makes software installation, updates, and dependency management easy.&lt;/p&gt;

&lt;p&gt;Remote Management: SSH (Secure Shell) support in Linux provides easy remote server management for DevOps teams.&lt;/p&gt;

&lt;p&gt;Linux and Operating System Foundations:&lt;br&gt;
Key Concepts Resource Management and Allocation How the OS allocates and manages CPU, memory, I/O devices, and processes.&lt;br&gt;
File Management Hierarchical file systems, permissions, and file operations.&lt;/p&gt;

&lt;p&gt;Device Management Managing hardware via device drivers.&lt;/p&gt;

&lt;p&gt;Security Authentication, authorization, user roles, and access control.&lt;/p&gt;

&lt;p&gt;Networking Network configuration, protocols, and services in Linux.&lt;/p&gt;

&lt;p&gt;Multi-user and Multitasking in Linux How Linux supports multiple users and processes at once.&lt;/p&gt;

&lt;p&gt;An Operating System's Components Kernel The central part of Linux that deals with hardware and system calls.&lt;br&gt;
Application Layer Graphical User Interfaces (GUIs) and Command Line Interfaces (CLIs) that are utilized to communicate with the OS.&lt;/p&gt;

&lt;p&gt;Interaction with the Kernel Through system calls, shell commands, and APIs.&lt;/p&gt;

&lt;p&gt;Briefing on the Big 3 Operating Systems Windows, macOS, and Linux: A Comparison&lt;br&gt;
User interface&lt;/p&gt;

&lt;p&gt;File system&lt;/p&gt;

&lt;p&gt;Customizability&lt;/p&gt;

&lt;p&gt;System performance&lt;/p&gt;

&lt;p&gt;Client OS vs. Server OS Use case differences, performance tuning differences, and feature differences.&lt;/p&gt;

&lt;p&gt;Why Linux is Used in DevOps&lt;/p&gt;

&lt;p&gt;Open-source and free&lt;/p&gt;

&lt;p&gt;Stability and performance&lt;/p&gt;

&lt;p&gt;Scripting and automation capabilities&lt;/p&gt;

&lt;p&gt;Massive community and toolset (e.g., Docker, Kubernetes, Ansible).&lt;/p&gt;

&lt;p&gt;Linux Commands That Every DevOps Engineer Should Know&lt;br&gt;
As a DevOps engineer, mastering certain Linux commands is essential for efficient system administration, automation, and troubleshooting. Here are some crucial Linux commands that every DevOps engineer should know:&lt;/p&gt;

&lt;p&gt;File and Directory Management&lt;br&gt;
ls: List files and directories.&lt;/p&gt;

&lt;p&gt;cd: Change the current directory.&lt;/p&gt;

&lt;p&gt;pwd: Print the current working directory.&lt;/p&gt;

&lt;p&gt;mkdir: Create a new directory.&lt;/p&gt;

&lt;p&gt;rm: Remove files and directories.&lt;/p&gt;

&lt;p&gt;cp: Copy files and directories.&lt;/p&gt;

&lt;p&gt;mv: Move or rename files and directories.&lt;/p&gt;

&lt;p&gt;find: Search for files and directories.&lt;/p&gt;

&lt;p&gt;chmod: Change file permissions.&lt;/p&gt;

&lt;p&gt;chown: Change file ownership.&lt;/p&gt;

&lt;p&gt;chgrp: Change file group ownership.&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;Text Manipulation and Viewing&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;cat: Concatenate and display file contents.&lt;/p&gt;

&lt;p&gt;grep: Search for patterns in files.&lt;/p&gt;

&lt;p&gt;head: Display the beginning of a file.&lt;/p&gt;

&lt;p&gt;tail: Display the end of a file.&lt;/p&gt;

&lt;p&gt;less: View file contents interactively.&lt;/p&gt;

&lt;p&gt;sed: Stream editor for text manipulation.&lt;/p&gt;

&lt;p&gt;awk: Text processing and data extraction tool.&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;Process and System Management&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;ps: View running processes.&lt;/p&gt;

&lt;p&gt;top: Monitor system resources and processes in real-time.&lt;/p&gt;

&lt;p&gt;kill: Terminate processes.&lt;/p&gt;

&lt;p&gt;systemctl: Manage system services.&lt;/p&gt;

&lt;p&gt;service: Control system services (older Linux distributions).&lt;/p&gt;

&lt;p&gt;df: Display disk space usage.&lt;/p&gt;

&lt;p&gt;du: Estimate file and directory disk usage.&lt;/p&gt;

&lt;p&gt;free: Display system memory usage.&lt;/p&gt;

&lt;p&gt;uptime: Show system uptime and load averages.&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;Networking&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;ping: Send ICMP echo requests to a host.&lt;/p&gt;

&lt;p&gt;curl or wget: Download files from the web.&lt;/p&gt;

&lt;p&gt;ssh: Securely connect to remote systems.&lt;/p&gt;

&lt;p&gt;scp: Securely copy files between systems.&lt;/p&gt;

&lt;p&gt;netstat: Network statistics and connections.&lt;/p&gt;

&lt;p&gt;ifconfig or ip: Network interface configuration.&lt;/p&gt;

&lt;p&gt;iptables or ufw: Firewall configuration.&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;Package Management&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;apt (Debian/Ubuntu) or yum (CentOS/RHEL): Package management commands for installing, updating, and removing software packages.&lt;/p&gt;

&lt;p&gt;dpkg (Debian/Ubuntu) or rpm (CentOS/RHEL): Package management commands for querying package information and managing individual packages.&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;Compression and Archiving&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;tar: Create and extract tar archives.&lt;/p&gt;

&lt;p&gt;gzip, gunzip, bzip2, unzip: Compress and decompress files.&lt;/p&gt;

&lt;p&gt;zip: Create and extract ZIP archives.&lt;/p&gt;

&lt;p&gt;📂 1. Listing Commands (ls)&lt;br&gt;
ls → 📋 List files and directories.&lt;/p&gt;

&lt;p&gt;ls -l → 📜 Detailed list with permissions, size, owner, etc.&lt;/p&gt;

&lt;p&gt;ls -a → 👀 Show hidden files.&lt;/p&gt;

&lt;p&gt;ls -lh → 📏 Human-readable file sizes.&lt;/p&gt;

&lt;p&gt;ls -d */ → 📁 List only directories.&lt;/p&gt;

&lt;p&gt;ls *.sh → 🛠️ Show only .sh files.&lt;/p&gt;

&lt;p&gt;🔹 Example:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;ls -lh&lt;br&gt;
ls -a&lt;/p&gt;

&lt;p&gt;📁 2. Directory Commands&lt;br&gt;
pwd → 📌 Show current directory path.&lt;/p&gt;

&lt;p&gt;cd folder → 🔄 Change directory.&lt;/p&gt;

&lt;p&gt;cd .. → ⬆️ Move one level up.&lt;/p&gt;

&lt;p&gt;cd - → 🔙 Switch to previous directory.&lt;/p&gt;

&lt;p&gt;cd ~ → 🏠 Go to the home directory.&lt;/p&gt;

&lt;p&gt;📂 Creating Directories (mkdir)&lt;br&gt;
mkdir newFolder → 🏗️ Create a new folder.&lt;/p&gt;

&lt;p&gt;mkdir .NewFolder → 👀 Create a hidden folder.&lt;/p&gt;

&lt;p&gt;mkdir A B C D → 📂 Create multiple folders at once.&lt;/p&gt;

&lt;p&gt;mkdir /home/user/Mydirectory → 📍 Create a folder in a specific location.&lt;/p&gt;

&lt;p&gt;mkdir -p A/B/C/D → 🔀 Create nested directories.&lt;/p&gt;

&lt;p&gt;🔹 Example:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;mkdir newFolder&lt;br&gt;
mkdir .NewFolder&lt;br&gt;
mkdir A B C D&lt;br&gt;
mkdir /home/user/Mydirectory&lt;br&gt;
mkdir -p A/B/C/D&lt;/p&gt;

&lt;p&gt;📂 Deleting Directories (rmdir, rm -r)&lt;br&gt;
rmdir folder → ❌ Remove empty directory.&lt;/p&gt;

&lt;p&gt;rm -r folder → 🚨 Remove non-empty directory.&lt;/p&gt;

&lt;p&gt;🔹 Example:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;rmdir emptyFolder&lt;br&gt;
rm -r oldFolder&lt;/p&gt;

&lt;p&gt;📄 3. File Management&lt;br&gt;
touch file.txt → 📄 Create a new empty file.&lt;/p&gt;

&lt;p&gt;cat file.txt → 📖 View file content.&lt;/p&gt;

&lt;p&gt;cp file1 file2 → 📑 Copy file.&lt;/p&gt;

&lt;p&gt;mv old new → ✏️ Rename/move file.&lt;/p&gt;

&lt;p&gt;rm file.txt → ❌ Delete a file.&lt;/p&gt;

&lt;p&gt;vim file.txt → ✍️ Open file in the Vim text editor.&lt;/p&gt;

&lt;p&gt;🔹 Example:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;touch notes.txt&lt;br&gt;
cp notes.txt backup.txt&lt;br&gt;
rm unwanted.txt&lt;br&gt;
vim myfile.txt&lt;/p&gt;

&lt;p&gt;🔎 4. Searching Files &amp;amp; Text&lt;br&gt;
find /path -name filename → 🔍 Find file by name.&lt;/p&gt;

&lt;p&gt;grep "word" file.txt → 🔎 Search inside a file.&lt;/p&gt;

&lt;p&gt;🔹 Example:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;find /home -name "notes.txt"&lt;br&gt;
grep "error" log.txt&lt;/p&gt;

&lt;p&gt;⚙️ 5. System &amp;amp; Process Management&lt;br&gt;
df -h → 💾 Check disk space.&lt;/p&gt;

&lt;p&gt;free -m → 🔋 Check RAM usage.&lt;/p&gt;

&lt;p&gt;top → 📊 View real-time system processes.&lt;/p&gt;

&lt;p&gt;kill PID → ❌ Stop a process of mentioned process ID (PID).&lt;/p&gt;

&lt;p&gt;🔹 Example:&lt;/p&gt;

&lt;p&gt;Copy&lt;/p&gt;

&lt;p&gt;df -h&lt;br&gt;
top&lt;br&gt;
kill 1234&lt;/p&gt;

</description>
      <category>devops</category>
      <category>linux</category>
    </item>
    <item>
      <title>2025 Reflection 2026 Outlook</title>
      <dc:creator>Kasim Hussain</dc:creator>
      <pubDate>Wed, 31 Dec 2025 17:18:22 +0000</pubDate>
      <link>https://forem.com/kasim_hussain_5f389fb5097/2025-reflection-2026-outlook-2b4a</link>
      <guid>https://forem.com/kasim_hussain_5f389fb5097/2025-reflection-2026-outlook-2b4a</guid>
      <description>&lt;p&gt;🌟 As I reflect on the rollercoaster that was 2025, I find myself filled with gratitude for every twist and turn that shaped my journey. This past year was a tapestry woven with both challenges and triumphs, each thread teaching me invaluable lessons that I will carry forward into 2026.&lt;/p&gt;

&lt;p&gt;There were moments when the weight of uncertainty felt heavy, when setbacks seemed insurmountable, and when doubt crept in like an unwelcome guest. Yet, through it all, I discovered the power of resilience. I learned that it’s not the challenges we face that define us, but how we respond to them. Each obstacle became an opportunity for growth, pushing me to dig deeper, think creatively, and embrace change.&lt;/p&gt;

&lt;p&gt;I also experienced the joy of connection—building relationships with incredible individuals who inspired me to reach higher and dream bigger. These connections reminded me that we are never alone in our journeys; we are part of a vibrant community that thrives on collaboration and support. Together, we can lift each other up and create a ripple effect of positivity.&lt;/p&gt;

&lt;p&gt;As I step into 2026, I do so with clarity and a renewed sense of purpose. I am ready to embrace new opportunities, tackle fresh challenges, and continue my journey of personal and professional growth. My mindset is anchored in positivity, and I am excited about what lies ahead. &lt;/p&gt;

&lt;p&gt;To anyone who faced their own ups and downs in 2025, remember: every experience is a stepping stone. Let’s carry the lessons learned into this new year and support one another as we chase our dreams. Here’s to resilience, growth, and the incredible possibilities that await us in 2026! 🚀&lt;/p&gt;

&lt;h1&gt;
  
  
  Resilience #GrowthMindset #NewBeginnings #CommunitySupport #2026Vision
&lt;/h1&gt;

</description>
    </item>
    <item>
      <title>👋 Hello Dev Community! My First Post 🚀</title>
      <dc:creator>Kasim Hussain</dc:creator>
      <pubDate>Tue, 23 Dec 2025 13:12:42 +0000</pubDate>
      <link>https://forem.com/kasim_hussain_5f389fb5097/hello-dev-community-my-first-post-4mjf</link>
      <guid>https://forem.com/kasim_hussain_5f389fb5097/hello-dev-community-my-first-post-4mjf</guid>
      <description>&lt;p&gt;Hi everyone! 👋&lt;br&gt;
This is my first post on Dev Community, and I’m really excited to be here.&lt;/p&gt;

&lt;p&gt;I’m currently learning DevOps and Cloud technologies, and I’ve decided to start sharing my learning journey publicly. I believe writing about what I learn helps me understand things better — and maybe it can help someone else too.&lt;/p&gt;

&lt;p&gt;🌱 What I’m Learning Right Now&lt;/p&gt;

&lt;p&gt;At the moment, I’m focusing on:&lt;/p&gt;

&lt;p&gt;AWS (Cloud fundamentals)&lt;/p&gt;

&lt;p&gt;Git &amp;amp; GitHub&lt;/p&gt;

&lt;p&gt;Linux&lt;/p&gt;

&lt;p&gt;CI/CD basics&lt;/p&gt;

&lt;p&gt;DevOps concepts and workflows&lt;/p&gt;

&lt;p&gt;I’m working mostly with hands-on labs and small practice projects, trying to understand how things work in real-world scenarios.&lt;/p&gt;

&lt;p&gt;🤝 Let’s Connect&lt;/p&gt;

&lt;p&gt;I’d love to connect with fellow learners and professionals.&lt;br&gt;
Feel free to say Hi, share feedback, or suggest topics I should write about!&lt;/p&gt;

&lt;p&gt;Thanks for reading, and happy coding! 💻✨&lt;/p&gt;

</description>
      <category>programming</category>
      <category>devops</category>
      <category>cloud</category>
    </item>
  </channel>
</rss>
