Linux Commands for Beginners

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As we know that the Operating System is an important component of the computer. Linux operating system is open-source and community-developed for mainframes, servers. Linux is one of the widely accepted operating systems across the world.

we will cover these topics: hide

1) Searching

2) File Commands

3) Hardware Information

4) Directory Navigation

5) File Compression

6) File Transfer

7) Users

8) Package Installation

9) Process Related

10) Network

11) Linux Keyboard Shortcuts

12) File Permission

13) Disk Usage

14) SSH Login

14.1) What to read next?

Searching

Search for a specific pattern in a file with:

grep [pattern] [file_name]

Recursively search for a pattern in a directory:

grep -r [pattern] [directory_name]

Find all files and directories related to a particular name:

locate [name]

List names that begin with a specified character [a] in a specified location [/folder/location] by using the find command:

find [/folder/location] -name [a]

See files larger than a specified size [+100M] in a folder:

find [/folder/location] -size [+100M]

File Commands

List files in the directory:

ls

List all files (shows hidden files):

ls -a

Show directory you are currently working in:

pwd

Create a new directory:

mkdir [directory]

Remove a file:

rm [file_name]

Remove a directory recursively:

rm -r [directory_name]

Recursively remove a directory without requiring confirmation:

rm -rf [directory_name]

Copy the contents of one file to another file:

cp [file_name1] [file_name2]

Recursively copy the contents of one file to a second file:

cp -r [directory_name1] [directory_name2]

Rename [file_name1] to [file_name2] with the command:

mv [file_name1] [file_name2]

Create a symbolic link to a file:

ln -s /path/to/[file_name] [link_name]

Create a new file:

touch [file_name]

Show the contents of a file:

more [file_name]

or use the cat command: This command used to create and view single or multiple files, and concatenate the files. It will consider one file output as another file input and print in the terminal or file.

cat [file_name]

Append file contents to another file:

cat [file_name1] >> [file_name2]

Display the first 10 lines of a file with:

head [file_name]

Show the last 10 lines of a file:

tail [file_name]

Encrypt a file:

gpg -c [file_name]

Decrypt a file:

gpg [file_name.gpg]

Show the number of words, lines, and bytes in a file:

wc

Hardware Information

Show bootup messages:

dmesg

See CPU information:

cat /proc/cpuinfo

Display free and used memory with:

free -h

List hardware configuration information:

lshw

See information about block devices:

lsblk

Show PCI devices in a tree-like diagram:

lspci -tv

Display USB devices in a tree-like diagram:

lsusb -tv

Show hardware information from the BIOS:

dmidecode

Display disk data information:

hdparm -i /dev/disk

Conduct a read-speed test on device/disk:

hdparm -tT /dev/[device]

Test for unreadable blocks on device/disk:

badblocks -s /dev/[device]

Directory Navigation

Move up one level in the directory tree structure:

cd ..

Change directory to $HOME:

cd

Change location to a specified directory:

cd /chosen/directory

File Compression

Archive an existing file:

tar cf [compressed_file.tar] [file_name]

Extract an archived file:

tar xf [compressed_file.tar]

Create a gzip compressed tar file by running:

tar czf [compressed_file.tar.gz]

Compress a file with the .gz extension:

gzip [file_name]

File Transfer

Copy a file to a server directory securely:

scp [file_name.txt] [server/tmp]

Synchronize the contents of a directory with a backup directory using the rsync command:

rsync -a [/your/directory] [/backup/]

Users

See details about the active users:

id

Show last system logins:

last

Display who is currently logged into the system with the who command:

who

Show which users are logged in and their activity:

Add a new group by typing:

groupadd [group_name]

Add a new user:

adduser [user_name]

Add a user to a group:

usermod -aG [group_name] [user_name]

Temporarily elevate user privileges to superuser or root using the sudo command:

sudo [command_to_be_executed_as_superuser]

Delete a user:

userdel [user_name]

Modify user information with:

usermod

Package Installation

List all installed packages with yum:

yum list installed

Find a package by a related keyword:

yum search [keyword]

Show package information and summary:

yum info [package_name]

Install a package using the YUM package manager:

yum install [package_name.rpm]

Install a package using the DNF package manager:

dnf install [package_name.rpm]

Install a package using the APT package manager:

apt-get install [package_name]

Install an .rpm package from a local file:

rpm -i  [package_name.rpm]

Remove an .rpm package:

rpm -e [package_name.rpm]

Install software from source code:

tar zxvf [source_code.tar.gz]
cd [source_code]
./configure
make
make install

Process Related

See a snapshot of active processes:

ps

Show processes in a tree-like diagram:

pstree

Display a memory usage map of processes:

pmap

See all running processes:

top

Terminate a Linux process under a given ID:

kill [process_id]

Terminate a process under a specific name:

pkill [proc_name]

Terminate all processes labelled “proc”:

killall [proc_name]

List and resume stopped jobs in the background:

bg

Bring the most recently suspended job to the foreground:

fg

Bring a particular job to the foreground:

fg [job]

List files opened by running processes:

lsof

Network

List IP addresses and network interfaces:

ip addr show

Assign an IP address to interface eth0:

ip address add [IP_address]

Display IP addresses of all network interfaces with:

ifconfig

See active (listening) ports with the netstat command:

netstat -pnltu

Show tcp and udp ports and their programs:

netstat -nutlp

Display more information about a domain:

whois [domain]

Show DNS information about a domain using the dig command:

dig [domain]

Do a reverse lookup on domain:

dig -x host

Do reverse lookup of an IP address:

dig -x [ip_address]

Perform an IP lookup for a domain:

host [domain]

Show the local IP address:

hostname -I

Download a file from a domain using the wget command:

wget [file_name]

Linux Keyboard Shortcuts

Kill process running in the terminal:

Ctrl + C

Stop current process:

Ctrl + Z

The process can be resumed in the foreground with fg or in the background with bg.

Cut one word before the cursor and add it to clipboard:

Ctrl + W

Cut part of the line before the cursor and add it to clipboard:

Ctrl + U

Cut part of the line after the cursor and add it to clipboard:

Ctrl + K

Paste from clipboard:

Ctrl + Y

Recall last command that matches the provided characters:

Ctrl + R

Run the previously recalled command:

Ctrl + O

Exit command history without running a command:

Ctrl + G

Run the last command again:

!!

Log out of current session:

exit

File Permission

Chown command in Linux changes file and directory ownership.

Assign read, write, and execute permission to everyone:

chmod 777 [file_name]

Give read, write, and execute permission to owner, and read and execute permission to group and others:

chmod 755 [file_name]

Assign full permission to owner, and read and write permission to group and others:

chmod 766 [file_name]

Change the ownership of a file:

chown [user] [file_name]

Change the owner and group ownership of a file:

chown [user]:[group] [file_name]

Disk Usage

You can use the df and du commands to check disk space in Linux.

See free and used space on mounted systems:

df -h

Show free inodes on mounted filesystems:

df -i

Display disk partitions, sizes, and types with the command:

fdisk -l

See disk usage for all files and directory:

du -ah

Show disk usage of the directory you are currently in:

du -sh

Display target mount point for all filesystem:

findmnt

Mount a device:

mount [device_path] [mount_point]

SSH Login

Connect to host as user:

ssh [email protected]

Securely connect to host via SSH default port 22:

ssh host

Connect to host using a particular port:

ssh -p [port] [email protected]

Connect to host via telnet default port 23:

telnet host