Linux command in DevOps

DevOps engineers use Linux every day because it’s free, fast, and easy to customize. More importantly, most DevOps tools like Docker, Kubernetes, Ansible, Terraform, and Jenkins are built to run best on Linux.

In DevOps, you often work on cloud servers (like AWS, Azure, or Google Cloud), and most of them run Linux by default. To manage these servers, engineers use Linux commands to move files, check logs, install software, run scripts, and fix problems. That’s why if you want to start a career in DevOps, learning Linux is one of the first and most important steps. It helps you work faster, solve problems easily, and use the tools that DevOps teams rely on every day.

In this article, we will first learn what Linux is, then understand its file system, and after that, we’ll go through some basic and important Linux commands that are useful in DevOps.

File System in Linux

In Linux, everything is represented as a file, including a hardware program. The files are stored in a directory, and every directory contains a file with a tree structure. That is called the file system hierarchy. Linux uses a single-rooted, inverted tree-like structure. The root directory is represented with / (forward slash). It is a top-level directory in Linux.

Basic command

In this section, we are going to discuss the basic commands of Linux:

1. pwd

The 'pwd' command helps you identify your current location in the file system :

   `pwd` - Print Working Directory     

2. ls

The 'ls' command is used to list the files and directories in the current directory :

  `ls` - List Files and Directories

3. uname

The 'uname' command retrieves system information:

   uname - Print System Information

Note : By adding `-r ` flag to the `uname` command , you can display the kernal release version.

uname -r   Print Kernel Release Information

4. cd

The 'cd' command allows you to navigate the file system by changing your current directory.

cd  -  Change Directory

5. clear

The 'clear' command clears the terminal screen, providing a clean workspace.

  clear - Clear the Terminal Screen

6. whoami

'whoami' returns the username of the current user logged into the terminal.

 whoami - Display the Current User 

7. History

'History' This command is used to display the history of the common that previously executed. history

history

8. free

'free' This command is used to check the memory-related detail in your system.

 free

9. nslookup

'nslookup' is used to obtain information for DNS server. It stands for Name Server Lookup.

nslookup <domain name>

10. ssh-keygen

'ssh-keygen' is used to establish a secure SSH connection from your host machine to any remote server. It generates a public/private key pair.

ssh-keygen -t rsa

11. curl

'curl' is a tool which is used to fetch data and post the data over the internet. it can used various of protocol like HTTPS , SMTP and FTP.

curl [options] [URL]

12 . curl -o

'curl -o' flag saves the data into a file on the local machine.

`curl -o` [file_name] [URL...]

13. apt-get

apt-get command used to manage packages in the linux. APT stand for the Advanced Packaging Tool , and its main used of install , update , upgrade and remove the packages.

apt-get [options] command

14. du

'du' command is used to check disk usage space.

du

15. df

'df'the is a command used to check the available disk space in system.

df -h

15. ifconfig

ifconfig is command is used to view the information about your network interface

ifconfig [OPTIONS] [INTERFACE]

16. ip

The command is a modern replacement of ifconfig command. It is used to view and manage network settings. You can check Ip addresses, configure network interfaces, view routing tables by this command.

ip [OPTIONS] OBJECT {COMMAND | help}

Creating Files and Directories

In DevOps, creating and managing files and directories is a common task. Here are some essential commands :

For Creating Directories

1 . For creating a single directory:

 mkdir GFG                                   

2. For creating multiple directories:

 mkdir GFG1 GFG2 GFG3                                                 

3. For creating directory paths (directories inside directories):

mkdir -p   /GFG/GFG1/GFG2

4. For creating a series of numbered directories:

 mkdir gfg{1..3}             

For Creating Files

We can create file in linux by using various commands like vi, touch, echo, nano etc. The following table will explain the use case of each command:

Copying and Pasting Files and Directories

The cp command is used for copying and pasting files or directories in Linux. Here are some commonly used options and examples:

1 . For copying a file with verbosity and force (overwrite if necessary):

cp -rvf  gfg1   gfg

Removing Files and Directories

To delete files or directories in DevOps, you can use the rm command. Be cautious, as it permanently removes data. Here's an example:

For removing a directory and its contents:

rm -rvf  gfg

Renaming Files and Directories

The mv command is used to rename files or directories. For example, to rename a directory from "gfg" to "gfg-devops," you can use:

mv gfg  gfg-devops      

User Management

User management in Linux is a crucial aspect of DevOps and system administration. Managing users and their permissions ensures that your systems are secure, organized, and meet the needs of your organization. Here's an overview of user management in Linux within a DevOps context:

1 . Creating a User

To create a new user in Linux, you can use the useradd command. For example:

sudo useradd  [usernam]

2. Setting a Password

After creating a user, set a password using the passwd command:

 sudo passwd [username]

3. Deleting a User

To delete a user, use the userdel command :

sudo userdel  [username]

4. Switch to Another User

The su command allows you to switch to another user's account by providing the username as an argument. To exit from the user's account and return to your original session, you can simply type 'exit'.

su  [USER NAME]

5. Rename the User

To change the username from the current name (oldname) to the new name (newname), use the following command.

sudo usermod -l [newname] [oldname]

Group Management

A group is a collection of user accounts that is very use full to administrators for managing and applying permission to a number users.

Process Management

A process management is the process of controlling and monitoring the process running on a Linux system.

1. ps

ps command displays currently running processes.

ps aux

2. top

The top command is used for memory monitoring. It shows a real-time view of system processes.

top

3. Kill

The kill command is used to terminate a process using it's PID.

kill 1234

Linux File System Permission

In linux , to increase the security of the file and directory. we need to used permission. There are total three type of file permission are Read , Write , Execute.

There are three type of file permission are as follow:

• user ( u ) : Permissions used for the user of the file.
• group( g ) : Permission used by the group member.
• other (o) : Permission used by all other users.

For example, suppose a file has read permissions that are allowed for the user. In this case, the user can only read that file, while the group and others will not be able to read it.

1 . ls -ld

It is used to check the permission of directory

 ls -ld

Permission with numeric & symbol

2. chmod

This command is used to change the permission of file and directory.

chmod <permission of user , group , other> {filename }

3. chown

It is used to change the owner of the file and directory.

chown [owner_name] [file name]

4. cat

It is used to read and concatenate the text inside the files. with help of this command we can displays the content inside the file.

cat <flag> {filename}

5. Grep (Global Regular Expression Print)

It filter searches a file for a particular pattern of characters , and displays all lines that contain the pattern.

grep <flag or search_word> {file name}

6. Sort

It print the output of a file, either alphabetically, numerically or by other specified way.

sort filename

7. head

The head command is used to display the first few lines of one or more text files.

head -n 2 gfg

8. tail

The tail command is used to display the last few lines of one or more text files.

tail -n 3 gfg

9. find

The find command is used to search files and directories based on different criteria such as name, size, type and modification date.

find [path] [expression]

Conclusion

In conclusion, this article has emphasized the vital role of Linux fundamentals in the toolkit of a DevOps professional. By providing insights into essential Linux commands and concepts, it equips individuals in the field to efficiently navigate file systems, manage users and groups, implement file permissions, and perform a variety of tasks critical for the success of DevOps operations, ultimately contributing to the security and functionality of their systems.