Touchbase with AWS CLI

Hey fellas, wishing you all Happy New Year. Today we are going to learn how to create simple scripts in AWS cli to gather important information of our deployed infrastructure.

The AWS management console is a very convenient way of gathering all this data. But when we require this information as some form of input for other reports/scripts, then AWS CLI comes into play.

AWS CLI vs SDK

AWS CLI acts like an API for communicating with the AWS services from the command line interface.

When an application needs to interact with AWS services, then we have to import AWS SDK in our code to communicate with the services.

Let's begin to extract all possible information from AWS command line interface aka CLI. By the end of this you will be accustomed with AWS CLI.

#Prerequisites

AWS CLI should be configured on your local machine with the AWS user having atleast read only permissions for the module that you are going to explore (EC2,RDS,S3)
If you are not able to run that command then you will be greeted with a message to contact your IAM administrator for granting privileges.

##Installation of AWS CLI tool

$ sudo pip install awscli

##Configuring AWS 

$ aws configure AWS Access Key ID [None]: DSLH546VSFAP AWS Secret Access Key [None]: jeoHhzr4FeEd9o6aOBicTK7kRvpJu5JRfFKFCe4yXw Default region name [None]: ap-south-1 Default output format [None]: <leave blank for default JSON format>


Required permission for accessing EC2 instances: AmazonEC2ReadOnlyAccess

Let us get our hands dirty and begin with the CLI commands to get the desired output:


Use case 1: To describe all of the EC2 instances in any of the mentioned output format.

aws ec2 describe-instances --output <table/json/text>

--output parameter: There are 3 formats in which we can get the output through CLI (table/json/text). the default output format is JSON, if we do not mention anything.


Use case 2: To describe all of the EC2 instances and filter out the information required like: InstanceId, Name, IpAddress, Public DNS address, Current State

--query parameter: Use to filter out the desired fields from the output

aws ec2 describe-instances --query "Reservations[*].Instances[*].{name: Tags[?Key=='Name'] | [0].Value, instance_id: InstanceId, ip_address: PrivateIpAddress, public_dns_name: PublicDnsName, state: State.Name}" --output table

  We can create alias if the command has to be used very frequently. Place the below lines under .bash_aliases file in the user home directory.

$ nano ~/.bash_aliases

alias aws_instances='aws ec2 describe-instances --query "Reservations[*].Instances[*].{name:Tags[?Key=='Name']|[0].Value, instance_id:InstanceId, state:State.Name, privateIP:PrivateIpAddress, AZ:Placement.AvailabilityZone, attached_vol:BlockDeviceMappings[0].Ebs.VolumeId, Security_grp:SecurityGroups[0].GroupName}" --output table'

$ source .bash_aliases

Use case 3: To describe all the mounted Volumes on all of the EC2 instances and filter out the Volume ID, Instance ID, Availability Zone, Size (GB) and Snapshot IDs

aws ec2 describe-volumes --query 'Volumes[*].[VolumeId, Attachments[0].InstanceId, AvailabilityZone, Size, SnapshotId, FakeKey]' --output text

We can attach/detach, create/delete volumes from EC2 instances. Also we can create snapshots.

Use case 4: To describe all the DB instances created under RDS and modifying their storage.

aws rds describe-db-instances --db-instance-identifier mydbinstance 

aws rds modify-db-instance \
--db-instance-identifier mydbinstance \
--allocated-storage 60 \
--apply-immediately

Use case 5: Creating an Instance from AWS CLI (for this we need EC2 admin privileges)

aws ec2 run-instances --image-id <ami-xxxxxxxx> --count 1 --instance-type t2.micro --key-name <MyKeyPair> --security-group-ids <sg-903004f8> --subnet-id <subnet-6e7f829e>
--iam-instance-profile  Name=ecsInstanceRole
--user-data file://bootstrap.txt (name of the file that has the bootstrap commands)

Overall I have looked into many basic commands under different modules EC2, RDS, S3 and ELB. The AWS CLI is a very deep and vast topic to cover on a blog.
We can control almost every service hosted on AWS through this powerful tool. Hope this blog has given you some motivation to take a deeper dive into the advance usage of AWS CLI.
See you folks on my next blog, till then keep learning.