Forem: Chirag Kumar

Filter & IO redirection command.

Chirag Kumar — Thu, 08 Aug 2024 08:41:20 +0000

Grep

grep command is used to find texts from any text input. Passwd file: stores information about all the users in the system.

➔ Finding line which contains word as “root” from /etc/passwd file.

➔ Linux is case sensitive, Root is different that root. Ignoring case in grep with -i option.

➔ To display things except the given word use -v option

Filter Commands

• less: Displays file content page wise or line wise. Ex: less /etc/passwd

• more

• head

• tail

• cut

• sed

I/O redirection

I/O redirection is accomplished using a redirection operator which allows the user to specify the input or output data be redirected to (or from) a file. Note that redirection always results in the data stream going to or coming from a file (the terminal is also considered a file).

➔ Create a file named DevOps tools with below content.

➔ Search for text “tech” replace it with “tools” and redirect output to a new file.

➔ Appending another output in same file with “>>” .

➔ Redirecting only error to a file “2>>”.

➔ Redirecting all the output to a file “&>>”.

Piping

So far we've dealt with sending data to and from files. Now we'll look at a mechanism for sending data from one program to another. It's called piping and the operator we use is ( | ). What this operator does is feed the output from the program on the left as input to the program on the right.

Find

The 'find' command is your go-to tool for locating files and directories in a Linux system. It's versatile, allowing you to search based on name, size, type, and other criteria. Let's dive into the basic usage of the 'find' command.

Types of files in Linux

Chirag Kumar — Thu, 08 Aug 2024 04:54:06 +0000

Symbolic links

Symbolic links are like desktop shortcuts we use in windows.
Create a soft link for /var/log directory in our current working directory.

VIM editor

Chirag Kumar — Tue, 06 Aug 2024 04:04:35 +0000

The acronym for Vim is Vi IMproved. Written by Bram Moolenaar, it is a free and open-source text editor. It was first released for UNIX variants in 1991, and its primary purpose was to develop the Vi editor, which was released back in 1976.

➔ Install vim editor.

➔ Open up a file in vim editor

➔ Hit i to enter into insert mode

=> type few lines => hit Esc

=> type :wq

=> Enter.
➔ Read file with cat command.

                          ## VIM EDITOR

VI Visual display editor

VIM Visual display editor improved

This is command mode editor for files. Other editors in Linux are emacs, gedit vi editor is most popular

It has 3 modes:

Command Mode
Insert mode (edit mode)
extended command mode

Note: When you open the vim editor, it will be in the command mode by default.

Command Mode:

gg - To go to the beginning of the page
G - To go to end of the page
w - To move the cursor forward, word by word
b - To move the cursor backward, word by word
nw - To move the cursor forward to n words (SW)
nb - To move the cursor backward to n words {SB)
u - To undo last change (word)
u - To undo the previous changes (entire line)
Ctrl+R - To redo the changes
VY - To copy a line
nyy - To copy n lines (Syy or 4yy)
P - To paste line below the cursor position
p - To paste line above the cursor position
dw - To delete the word letter by letter {like Backspace}
X - To delete the world letter by letter (like DEL Key)
dd - To delete entire line
ndd - To delete n no. of lines from cursor position{Sdd)
I - To search a word in the file

Extended Mode: ( Colon Mode)

Extended Mode is used for save and quit or save without quit using "Esc" Key with":"

Esc+:w - To Save the changes
Esc+:q - To quit (Without saving)
Esc+:wq - To save and quit
Esc+:w! - To save forceful
Esc+wq! - To save and quit forcefully
Esc+:x - To save and quit
Esc+:X - To give passwd or d to the file and remove password
Esc+:20(n) - To go to line no 20 or n
Esc+: se nu - To set the line numbers to the file
Esc+:se nonu - To remove a set line number

Is command options

Basic CLI Commands

Chirag Kumar — Sun, 04 Aug 2024 19:15:04 +0000

➔ Open Terminal

➔ Know where you are? Present Working Directory

➔ Create a directory/folder in your home directory

➔ Change your current working directory to linux-practices(Go to linux-practices folder).

➔ Create some more directories and list them with “ls” command.

➔ Create some empty files with “touch” command and list them.

➔ Reconfirm your location in your system

Absolute path and Relative path

What is a path?

A path is a unique location of a file or a folder in a file system of an OS. A path to a file is a combination of / and alpha-numeric characters.

What is an absolute path?

An absolute path is defined as specifying the location of a file or directory from the root directory(/). In other words, an absolute path is a complete path from the start of the actual filesystem from the / directory.

Some examples of the absolute path:
/home/imran/linux-practices/
/var/ftp/pub
/etc/samba.smb.conf
/boot/grub/grub.conf

If you see all these paths started from the / directory which is a root directory for every Linux/Unix machine.

What is the relative path?

The relative path is a path related to the present working directory(pwd). Suppose I am located in /home/imran and I want to change the directory to /home/imran/linux-practices. I can use the relative path concept to change the directory to Linux practices and also the devopsdir directory.

If you see all these paths did not start with / directory.
➔ Creating directories in devopsdir directory with absolute and relative path.

➔ Copying files into directory.

➔ Copying directories from one location to another.

➔ Moving files from one location to another.

➔ Removing files and directories.

Difference between RPM based and Debian based.

Chirag Kumar — Sun, 04 Aug 2024 05:16:39 +0000

From the user’s point of view, there isn’t much difference in these tools. The RPM and DEB formats are both just archive files, with some metadata attached to them. They are both equally arcane, have hardcoded install paths, and only differ in subtle details. DEB files are installation files for Debian-based distributions. RPM files are installation files for Red Hat-based distributions. Ubuntu is based on Debian’s package management, which is based on APT and DPKG. Red Hat, CentOS, and Fedora are based on the old Red Hat Linux package management system, RPM.

DEB or .deb (Debian-based software)
DEB is the extension of the Debian software package format and the most often-used name for such binary packages. DEB was developed by Bedian.

Example: Google Chrome software
Package name: google-chrome-stable_current_amd64.deb
Installation: dpkg -i google-chrome-stable_current_amd64.deb

RPM or .rpm (Red Hat-based software.)
It is a package management system. The name RPM variously refers to the .rpm file format, files in this format, software packaged in such files, and the package manager itself. RPM was intended primarily for Linux distributions; the file format is the baseline package format of the Linux Standard Base. RPM was developed by Community & Red Hat.

Example: Google Chrome software
Package Name: google-chrome-stable-57.0.2987.133-1.x86_64.rpm
Installation: rpm -ivh google-chrome-stable-57.0.2987.133-1.x86_64.rpm

NOTE: You will also encounter different commands, packages, and service names while using both kinds of distros.

Lets get move forward to some more useful things here are some more Important and useful Directories.

Some Important Directories

Home Directories: /root,/home/username
User Executable: /bin, /usr/bin, /usr/local/bin
System Executables: /sbin, /usr/sbin, /usr/local/sbin
Other Mountpoints: /media, /mnt
Configuration: /etc
Temporary Files: /tmp
Kernels and Bootloader: /boot
Server Data: /var, /srv
System Information: /proc, /sys
Shared Libraries: /lib, /usr/lib, /usr/local/lib

Linux

Chirag Kumar — Sat, 03 Aug 2024 09:34:57 +0000

Hello everyone, welcome to my DevOps learning journey.

In this journey, we will be focusing on learning DevOps, and the first topic we'll cover is Linux. Linux is a free, open-source operating system that plays a significant role in DevOps for handling various tasks and processes.

what is Linux :-
Linux is a free, open source operating system, released under the GNU General Public License (GPL). Anyone can run, study, modify, and redistribute the source code, or even sell copies of their modified code, as long as they do so under the same license.

Intro to Linux
Basic CLI Commands
Understanding files in Linux
Filters & Redirection
Users & Group
Sudo
Software management
Services & Processes
Good to know commands
Server Management

Linux Principles

Everything is a file (Including Hardware)
Small Single purpose Programs
Ability to chain programs together for complex operations
Avoid Captive User Interface
Configuration data stored in text

Why Linux?

Opensource
Community Support
Support Wide Variety of Hardware
Customization
Most Servers runs on Linux
Automation
Security

Popular Linux distros

➔ Popular Desktop Linux OS

Ubuntu Linux
Linux Mint
Arch Linux
Fedora
Debian
OpenSUSE

Popular Server Linux OS

Red Hat Enterprise Linux
Ubuntu Server
Centos
SUSE Enterprise Linux

Most used Linux distros currently in IT industry

RPM based:- RHEL, Centos, Oracle Linux
Debian based :- Ubuntu Server, Kali Linux

Practice Linux & Vagrant

Website
On Centos7
Httpd service & HTML Templates
WordPress
On Ubuntu 18
Apache2, MySQL & PHP WordPress Template
Automation
Vagrant provisioning