Understanding AWS S3 cp Command

AWS S3 is a managed cloud storage service that is scalable and has a wide range of use cases. It’s known for its reliability, speed, and cost-effectiveness. One of the key functionalities within AWS S3 is the aws s3 cp command.

Introduction to aws s3 cp

In the AWS Command Line Interface (CLI), aws s3 cp is used to copy files or objects to and from Amazon S3 buckets. This command is essential for managing data in AWS S3, providing an effective way to move files between your local system and S3 storage.

Basic Usage

The most basic form of the command looks like this:

aws s3 cp source destination

Where ‘source’ is the file or S3 object you want to copy, and ‘destination’ is where you want to copy it to. Paths can be either local filesystem paths or S3 URIs, which follow the format s3://bucket-name/path.

Copying a Local File to an S3 Bucket

To upload a file from your local system to an S3 bucket, use:

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

This command uploads localfilename.txt to the bucket named mybucket under the root directory. You can also specify a directory structure within the bucket:

aws s3 cp localfilename.txt s3://mybucket/folder1/subfolder2/

Copying a File from an S3 Bucket to Local

Downloading a file from an S3 bucket to your local machine is just as straightforward:

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

If the destination is not specified, the file will be saved with its current name in the current directory. Directories can also be specified for more organized downloads:

aws s3 cp s3://mybucket/filename.txt /local/path/filename.txt

Recursive Copying

The --recursive flag allows you to copy entire directories. This is useful for bulk uploads and downloads:

aws s3 cp mydirectory s3://mybucket/ --recursive

This command uploads all files and subdirectories within mydirectory to mybucket. Conversely, to download an entire directory:

aws s3 cp s3://mybucket/mydirectory/ ./localdirectory --recursive

Manage Metadata and ACLs

The aws s3 cp command allows for manipulation of metadata and Access Control Lists (ACLs). You can add metadata to your file:

aws s3 cp localfilename.txt s3://mybucket/ --metadata key1=value1,key2=value2

You can also set the ACL, such as making a file public:

aws s3 cp localfilename.txt s3://mybucket/ --acl public-read

Handling Large Files

For files larger than 160 MB, AWS CLI automatically switches to multipart uploads, improving transfer efficiency. To customize multipart upload settings, use the following parameters:

• --multipart-chunk-size-mb to set the size of each part.
• --no-multipart to disable multipart uploads.

aws s3 cp largefile.iso s3://mybucket/ --multipart-chunk-size-mb 50

Managing Transfer Speed

Transfer speed can be managed through the --storage-class parameter. The default storage class is STANDARD, but you can set it to REDUCED_REDUNDANCY, INTELLIGENT_TIERING, ONEZONE_IA, or others:

aws s3 cp localfile.zip s3://mybucket/ --storage-class ONEZONE_IA

Using the –dryrun Option

The --dryrun option is useful for testing commands without making any actual changes. This flag shows what would have happened:

aws s3 cp localfilename.txt s3://mybucket/ --dryrun

Combining with Filters

When using --recursive, you can combine it with --exclude and --include filters to control what files are copied:

aws s3 cp mydir s3://mybucket/ --recursive --exclude *.tmp --include *.txt

This command uploads all .txt files from mydir while excluding .tmp files.

Logging

Tracking and logging your aws s3 cp operations can be helpful for audits or debugging. Use the --debug flag for detailed information:

aws s3 cp source destination --debug

You can also redirect output to a log file:

aws s3 cp source destination > output.log 2>&1

Security Considerations

Ensure your AWS CLI configuration is secure. Always use access keys with limited permissions, and follow best practices such as using IAM roles. For sensitive data, consider encrypted storage classes and S3 bucket policies that enforce encryption:

aws s3 cp localfile.txt s3://mybucket/ --sse AES256

This command enables server-side encryption using AES-256.

Cross-Region Copying

Copying files between S3 buckets in different regions is seamless. Specify the source and destination buckets:

aws s3 cp s3://source-bucket/filename.txt s3://destination-bucket/filename.txt

Ensure you have the necessary IAM permissions to access both regions.

Examples

Here are a few practical examples:

• Upload a file:

aws s3 cp image.png s3://mybucket/images/

• Download a file:

aws s3 cp s3://mybucket/documents/resume.pdf ./resume.pdf

• Copy a directory recursively:

aws s3 cp s3://mybucket/data/ ./localdata --recursive

• Upload with metadata and public access:

aws s3 cp video.mp4 s3://mybucket/videos/ --metadata author=JohnDoe --acl public-read

• Use filters and recursion:

aws s3 cp logs/ s3://mybucket/logs/ --recursive --exclude * --include *.log

The aws s3 cp command is versatile and robust, making data management in the cloud more accessible and efficient. Mastering its various options can significantly improve your workflow and ensure better data handling practices.