Aws Cli

What is AWS CLI?

AWS CLI is a tool that allows you to manage AWS services using commands from your terminal or command prompt.

Instead of opening the AWS Console in a browser, you can:

Create EC2 instances
List S3 buckets
Upload files to S3
Check IAM users
Manage almost all AWS services
All from one place using commands.

In short:

AWS CLI = Control AWS using terminal commands

Why Should We Use AWS CLI?

Here are some simple reasons:
- Faster than AWS Console
- Easy to automate tasks
- Very useful in DevOps
- Can be used in scripts and CI/CD pipelines
- Same commands work everywhere

If you want to move into DevOps or Cloud roles, AWS CLI is mandatory.

Prerequisites

Before using AWS CLI, you need:

An AWS account
IAM user with programmatic access
Access Key ID
Secret Access Key

You should never use the root account for CLI access.

Installing AWS CLI

On Linux (Ubuntu)

sudo apt update
sudo apt install awscli -y

Check version:

aws --version

On Windows

Download AWS CLI MSI installer from AWS official site
Install it like a normal software
Open Command Prompt and check:

aws --version

Configuring AWS CLI

After installation, you must configure AWS CLI.

Run:

aws configure

It will ask:

AWS Access Key ID: xxxxxxxxx
AWS Secret Access Key: xxxxxxxxx
Default region name: ap-south-1
Default output format: json

Now your AWS CLI is connected to your AWS account.

AWS CLI Configuration Files

AWS CLI stores configuration in two files:

~/.aws/credentials
~/.aws/config

You can check them using:

cat ~/.aws/credentials
cat ~/.aws/config

Basic AWS CLI Commands

Check AWS Identity

aws sts get-caller-identity

This command confirms:

Which account you are using

Which IAM user is configured

AWS S3 Commands

List all S3 Buckets

  aws s3 ls

Create an S3 Bucket

  aws s3 mb s3://my-first-cli-bucket

Upload File to S3

  aws s3 cp file.txt s3://my-first-cli-bucket/

Download File from S3

  aws s3 cp s3://my-first-cli-bucket/file.txt .

Delete File from S3

  aws s3 rm s3://my-first-cli-bucket/file.txt

Delete S3 Bucket

  aws s3 rb s3://my-first-cli-bucket --force

AWS EC2 Commands

List EC2 Instances

  aws ec2 describe-instances

This command gives full details of all instances in JSON format.

List Only Instance IDs

  aws ec2 describe-instances \
  --query "Reservations[].Instances[].InstanceId"

Start EC2 Instance

  aws ec2 start-instances --instance-ids i-1234567890abcdef0

Stop EC2 Instance

  aws ec2 stop-instances --instance-ids i-1234567890abcdef0

Terminate EC2 Instance

  aws ec2 terminate-instances --instance-ids i-1234567890abcdef0

Be careful. This action is permanent.

AWS IAM Commands

List IAM Users

  aws iam list-users

List IAM Roles

  aws iam list-roles

Get IAM User Details

  aws iam get-user

Working With AWS Regions

List All Regions

  aws ec2 describe-regions

Run Command in Specific Region

  aws ec2 describe-instances --region us-east-1

Output Formats in AWS CLI

AWS CLI supports:

json
table
text

Example:

    aws ec2 describe-instances --output table

Table output is easier to read.

AWS CLI Help Command

Whenever you are stuck, use:

    aws help

Or for a specific service:

    aws s3 help

This is very useful for beginners.

Common AWS CLI Errors

Access Denied

Reason:

IAM user does not have required permissions

Solution:

Attach correct IAM policy

Invalid Client Token