Essential Linux Shell Commands and SSH Basics

Introduction to Linux Shell

User Shell Prompts

• Regular User: $

• Root User: #

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Logging into a Remote System

Using SSH with Password

[user@host ~]$ ssh remoteuser@remotehost

Using SSH with Private Key

• Ensure the private key has the correct permissions:

[user@host ~]$ chmod 600 privatekey.pem

• Connect using the private key:

[user@host ~]$ ssh -i privatekey.pem remoteuser@remotehost

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Logging Out from a Remote System

• Use the exit command:

exit

• Alternatively, press Ctrl + D.

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Executing Commands in the Bash Shell

Basic Commands

• Display current user:

whoami

• Display file contents:

cat

• Display the first few lines of a file:

head -n {number}

• Display the last few lines of a file:

tail -n {number}

Date Command Options

• Display date in RFC-2822 format:

date -R

• Display date as seconds since 1970-01-01 00:00:00 UTC:

date -s

• Display date in a specific format (customizable):

date -x

Running Multi-Line Commands

Use a backslash (\) to continue a command on the next line:

echo "This is a long command" \

"that spans multiple lines."

Viewing Command History

• List previously executed commands:

[user@host ~]$ history

• Re-run a command by number:

!number

• Re-run the most recent command starting with a specific string:

!string

• Insert the last word of the previous command:

• Use Esc + . or Alt + .

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Editing Commands on the Command Line

Useful Keyboard Shortcuts

Shortcut	Description
Ctrl + A	Move to the beginning of the line
Ctrl + E	Move to the end of the line
Ctrl + U	Clear from beginning to cursor
Ctrl + K	Clear from cursor to the end
Ctrl + Left Arrow	Move to the beginning of the previous word
Ctrl + Right Arrow	Move to the end of the next word
Ctrl + R	Search through command history