Uploading and downloading objects in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an object in AWS S3?

An object in AWS S3 is a file stored in a bucket. It includes the data itself, metadata, and a unique identifier called a key.

beginner

How do you upload a file to an S3 bucket using the AWS Management Console?

You open the S3 bucket, click 'Upload', select the file from your computer, and then click 'Upload' to store it in the bucket.

beginner

What is the purpose of the 'key' when uploading an object to S3?

The key is the unique name that identifies the object within the bucket, like a filename in a folder.

intermediate

Name one method to download an object from S3 using the AWS CLI.

You can use the command 'aws s3 cp s3://bucket-name/object-key local-file-path' to download an object.

intermediate

What is a pre-signed URL in the context of S3 object downloads?

A pre-signed URL is a temporary link that allows anyone with the URL to download the object without needing AWS credentials.

Which AWS service is used to store and retrieve objects like files and images?

A Amazon Lambda

B Amazon EC2

C Amazon S3

D Amazon RDS

Amazon S3 is the service designed for object storage, ideal for files and images.

What does the 'key' represent when uploading an object to S3?

A The bucket name

B The size of the object

C The encryption method

D The unique name of the object in the bucket

The key is the unique identifier or name of the object inside the bucket.

Which AWS CLI command downloads an object from S3 to your local machine?

A aws s3 cp

B aws s3 ls

C aws s3 rm

D aws s3 mv

'aws s3 cp' copies files between S3 and your local system, used for downloads and uploads.

What is the main benefit of using a pre-signed URL for downloading an S3 object?

A It encrypts the object permanently

B It allows temporary access without AWS credentials

C It compresses the object automatically

D It deletes the object after download

Pre-signed URLs grant temporary access to objects without requiring AWS login.

Which of the following is NOT a valid way to upload an object to S3?

A Using Amazon EC2 to directly store files

B Using AWS Management Console

C Using AWS SDK in code

D Using AWS CLI command 'aws s3 cp'

Amazon EC2 is a compute service, not used directly for storing objects like S3.

Explain the steps to upload a file to an S3 bucket using the AWS CLI.

Think about the command format to copy files to S3.

Describe how a pre-signed URL works for downloading objects from S3 and why it is useful.

Consider how you might share a private file safely.

Practice

1. What does uploading an object to an AWS S3 bucket mean?

easy

A. Deleting a file from the cloud storage

B. Saving a file from your computer to the cloud storage

C. Copying a file from one folder to another on your computer

D. Viewing a file stored in the cloud without downloading

Solution

1. Step 1: Understand uploading concept

   Uploading means moving or saving a file from your local device to a remote place, like cloud storage.

2. Step 2: Apply to AWS S3 context

   In AWS S3, uploading an object means saving your local file into an S3 bucket in the cloud.

3. Final Answer:

   Saving a file from your computer to the cloud storage -> Option B

4. Quick Check:

   Uploading = Save local file to cloud [OK]

Hint: Uploading means sending files from your PC to cloud storage [OK]

Common Mistakes:

• Confusing uploading with downloading
• Thinking uploading deletes files
• Mixing local file moves with cloud uploads

2. Which AWS CLI command correctly uploads a file named photo.jpg to a bucket called mybucket?

easy

A. aws s3 get photo.jpg s3://mybucket/

B. aws s3 download photo.jpg s3://mybucket/

C. aws s3 cp photo.jpg s3://mybucket/

D. aws s3 remove photo.jpg s3://mybucket/

Solution

1. Step 1: Identify correct AWS CLI upload command

   The command to upload files to S3 is aws s3 cp followed by the local file and the bucket path.

2. Step 2: Match command with given file and bucket

   Using aws s3 cp photo.jpg s3://mybucket/ uploads the file photo.jpg to the bucket mybucket.

3. Final Answer:

   aws s3 cp photo.jpg s3://mybucket/ -> Option C

4. Quick Check:

   Upload command = aws s3 cp [OK]

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

Common Mistakes:

• Using 'download' instead of 'cp' for upload
• Confusing 'get' with upload command
• Using 'remove' which deletes files

3. What will be the result of this AWS CLI command?
aws s3 cp s3://mybucket/report.pdf ./

medium

A. Downloads report.pdf from the bucket to current folder

B. Uploads report.pdf from local to the bucket

C. Deletes report.pdf from the bucket

D. Lists all files in the bucket

Solution

1. Step 1: Understand the command structure

   The command aws s3 cp copies files. The source is s3://mybucket/report.pdf and destination is ./ (current folder).

2. Step 2: Determine direction of copy

   Since source is S3 and destination is local, the file is downloaded from the bucket to the local folder.

3. Final Answer:

   Downloads report.pdf from the bucket to current folder -> Option A

4. Quick Check:

   Source S3 to local = download [OK]

Hint: Source path starting with s3:// means download to local [OK]

Common Mistakes:

• Thinking 'cp' always uploads
• Confusing source and destination order
• Assuming it deletes files

4. You run this command to download a file but get an error:
aws s3 cp s3://mybucket/data.csv ./
What is the most likely cause?

medium

A. You forgot to add --recursive flag

B. You used the wrong command; should be aws s3 upload

C. The local folder ./ does not exist

D. The file data.csv does not exist in the bucket

Solution

1. Step 1: Analyze the error context

   The command is correct for downloading a single file. An error usually means the file is missing or inaccessible.

2. Step 2: Check common causes

   If the file data.csv is not in the bucket, the command fails. The local folder ./ always exists as current directory, and --recursive is not needed for single files.

3. Final Answer:

   The file data.csv does not exist in the bucket -> Option D

4. Quick Check:

   Missing file in bucket causes download error [OK]

Hint: Check if file exists in bucket before downloading [OK]

Common Mistakes:

• Using wrong command for download
• Assuming local folder missing causes error
• Adding unnecessary flags

5. You want to upload all files from your local folder photos/ to the S3 bucket mybucket preserving folder structure. Which command should you use?

hard

A. aws s3 sync photos/ s3://mybucket/

B. aws s3 cp photos/ s3://mybucket/

C. aws s3 cp photos/ s3://mybucket/ --no-recursive

D. aws s3 mv photos/ s3://mybucket/ --recursive

Solution

1. Step 1: Understand folder upload options

   To upload multiple files preserving folder structure, aws s3 sync is preferred as it copies all files and folders efficiently.

2. Step 2: Compare commands

   aws s3 cp --recursive can copy folders but sync is better for syncing changes and preserving structure. mv moves files (deletes local), which may not be desired.

3. Final Answer:

   aws s3 sync photos/ s3://mybucket/ -> Option A

4. Quick Check:

   Use 'sync' to upload folders preserving structure [OK]

Hint: Use 'aws s3 sync' for folder uploads preserving structure [OK]

Common Mistakes:

• Using 'cp' without --recursive for folders
• Using 'mv' which deletes local files
• Forgetting to preserve folder structure