Basic CLI commands (s3, ec2) in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Understanding AWS S3 Bucket Creation Behavior

You run the command aws s3 mb s3://my-unique-bucket-12345. What is the expected result if the bucket name is globally unique and you have permissions?

AWS

aws s3 mb s3://my-unique-bucket-12345

A The bucket is created and a success message is shown.

B The command lists all existing buckets instead of creating one.

C The command fails with an error about invalid bucket name.

D The command creates a folder inside an existing bucket.

💡 Hint

Think about what mb means in the AWS S3 CLI.

The aws s3 mb command means 'make bucket'. If the bucket name is unique and you have permission, it creates the bucket and shows a success message.

❓ Configuration

intermediate

Correct AWS CLI Command to List EC2 Instances

Which AWS CLI command correctly lists all EC2 instances in the default region?

A aws ec2 get-instances

B aws ec2 list-instances

C aws ec2 show-instances

D aws ec2 describe-instances

💡 Hint

Think about the AWS CLI command that describes resources.

The correct command to list EC2 instances is aws ec2 describe-instances. Other options are invalid commands.

❓ Architecture

advanced

Choosing the Right AWS CLI Command for EC2 Instance State Change

You want to stop an EC2 instance with ID i-0abcd1234efgh5678 using AWS CLI. Which command will correctly stop the instance?

A aws ec2 stop-instances --instance-ids i-0abcd1234efgh5678

B aws ec2 start-instances --instance-ids i-0abcd1234efgh5678

C aws ec2 reboot-instances --instance-ids i-0abcd1234efgh5678

D aws ec2 terminate-instances --instance-ids i-0abcd1234efgh5678

💡 Hint

Stopping an instance is different from terminating or rebooting it.

The stop-instances command stops the instance without deleting it. Terminate deletes it, reboot restarts it, and start turns it on.

❓ security

advanced

AWS CLI Command Impact on S3 Bucket Permissions

You run aws s3 cp file.txt s3://mybucket/ without specifying any ACL options. What is the default permission behavior for the uploaded file?

AWS

aws s3 cp file.txt s3://mybucket/

A The file is uploaded with public read permissions.

B The file is uploaded with private permissions, accessible only to the bucket owner.

C The file is uploaded with permissions inherited from the bucket policy.

D The upload fails due to missing ACL specification.

💡 Hint

Think about default ACL behavior when none is specified.

By default, files uploaded to S3 are private and accessible only to the bucket owner unless ACL options are specified.

✅ Best Practice

expert

Best Practice for AWS CLI EC2 Instance Tagging During Launch

You want to launch an EC2 instance and tag it with Environment=Production using a single AWS CLI command. Which command correctly achieves this?

A aws ec2 run-instances --image-id ami-12345678 --count 1 --instance-type t2.micro --tag Key=Environment Value=Production

B aws ec2 run-instances --image-id ami-12345678 --count 1 --instance-type t2.micro --tags Key=Environment,Value=Production

C aws ec2 run-instances --image-id ami-12345678 --count 1 --instance-type t2.micro --tag-specifications 'ResourceType=instance,Tags=[{Key=Environment,Value=Production}]'

D aws ec2 run-instances --image-id ami-12345678 --count 1 --instance-type t2.micro --tag-specifications 'Tags=[{Key=Environment,Value=Production}]'

💡 Hint

Tagging requires specifying resource type and tags in a specific format.

The --tag-specifications option requires the resource type and tags in JSON-like syntax. Only option C uses the correct syntax.

Practice

1. Which AWS CLI command lists all buckets in Amazon S3?

easy

A. aws s3 list-buckets

B. aws ec2 ls

C. aws ec2 describe-buckets

D. aws s3 ls

Solution

1. Step 1: Understand the service for buckets

   Amazon S3 stores buckets, so the command must use aws s3.

2. Step 2: Identify the correct action to list buckets

   The ls action lists buckets in S3. So aws s3 ls lists all buckets.

3. Final Answer:

   aws s3 ls -> Option D

4. Quick Check:

   List buckets = aws s3 ls [OK]

Hint: Use 'aws s3 ls' to list buckets quickly [OK]

Common Mistakes:

• Confusing EC2 commands with S3 commands
• Using 'list-buckets' which is not a valid CLI action
• Trying to list buckets with 'aws ec2' commands

2. Which command correctly starts an EC2 instance with ID i-1234567890abcdef0?

easy

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

B. aws ec2 start-instance --instance-ids i-1234567890abcdef0

C. aws ec2 start-instances --instance-id i-1234567890abcdef0

D. aws ec2 start-instance --instance-id i-1234567890abcdef0

Solution

1. Step 1: Identify the correct EC2 start command

   The correct command to start instances is start-instances (plural).

2. Step 2: Use the correct option name for instance IDs

   The option is --instance-ids (plural), not --instance-id.

3. Final Answer:

   aws ec2 start-instances --instance-ids i-1234567890abcdef0 -> Option A

4. Quick Check:

   Start instances = start-instances + --instance-ids [OK]

Hint: Use plural 'start-instances' and '--instance-ids' options [OK]

Common Mistakes:

• Using singular 'start-instance' instead of 'start-instances'
• Using '--instance-id' instead of '--instance-ids'
• Mixing up EC2 and S3 commands

3. What is the output of this command if the bucket my-bucket contains two files file1.txt and file2.txt?

aws s3 ls s3://my-bucket/

medium

A. Lists the names and sizes of file1.txt and file2.txt

B. Shows an error: bucket not found

C. Lists only the bucket name my-bucket

D. Deletes the files in the bucket

Solution

1. Step 1: Understand the command purpose

   aws s3 ls s3://my-bucket/ lists objects inside the bucket my-bucket.

2. Step 2: Predict the output for files in the bucket

   The command will show the file names and their sizes for file1.txt and file2.txt.

3. Final Answer:

   Lists the names and sizes of file1.txt and file2.txt -> Option A

4. Quick Check:

   List bucket contents = file names + sizes [OK]

Hint: Use 'aws s3 ls s3://bucket/' to list files inside [OK]

Common Mistakes:

• Thinking it lists buckets instead of files
• Expecting deletion or error output
• Confusing bucket name listing with object listing

4. You run this command but get an error: aws ec2 describe-instances --instance-ids i-1234567890abcdef0. What is the likely cause?

medium

A. The command should be aws s3 describe-instances

B. The instance ID is incorrect or does not exist

C. You must use start-instances instead of describe-instances

D. You forgot to add --bucket option

Solution

1. Step 1: Check command correctness

   aws ec2 describe-instances --instance-ids is a valid command to get instance details.

2. Step 2: Identify common error reasons

   An error usually means the instance ID is wrong or the instance does not exist in your account or region.

3. Final Answer:

   The instance ID is incorrect or does not exist -> Option B

4. Quick Check:

   Invalid instance ID causes describe-instances error [OK]

Hint: Check instance ID spelling and region for describe-instances errors [OK]

Common Mistakes:

• Using S3 commands for EC2 tasks
• Confusing describe with start commands
• Adding irrelevant options like --bucket

5. You want to copy a local file photo.jpg to an S3 bucket my-photos in a folder 2024/. Which command correctly does this?

hard

A. aws ec2 cp photo.jpg s3://my-photos/2024/

B. aws s3 mv photo.jpg s3://my-photos/2024/

C. aws s3 cp photo.jpg s3://my-photos/2024/

D. aws s3 sync photo.jpg s3://my-photos/2024/

Solution

1. Step 1: Choose the correct AWS service and action

   Copying files to S3 uses aws s3 cp. EC2 commands do not handle S3 files.

2. Step 2: Use the correct source and destination syntax

   Source is local file photo.jpg, destination is S3 path s3://my-photos/2024/.

3. Final Answer:

   aws s3 cp photo.jpg s3://my-photos/2024/ -> Option C

4. Quick Check:

   Copy local file to S3 = aws s3 cp [OK]

Hint: Use 'aws s3 cp' to copy files to S3 buckets [OK]

Common Mistakes:

• Using 'mv' which moves instead of copies
• Using 'sync' for single file copy
• Using EC2 commands for S3 file operations