Question
Answer and Explanation
The AWS S3 command-line interface (CLI) provides two primary commands for transferring data: s3 cp and s3 sync. While both are used for copying data to and from Amazon S3, they operate differently and serve different purposes. Here's a breakdown of their differences:
1. `aws s3 cp` (Copy):
- The `aws s3 cp` command is designed to copy individual files or directories from one location to another. It functions similarly to the standard cp command in Unix-like systems.
- It can copy files between:
- Local file system to S3.
- S3 to local file system.
- S3 to S3 (within the same or different buckets).
- If you specify a directory as the source, it copies all files within that directory non-recursively. To copy recursively, you must use the --recursive or --recursive flag.
- `aws s3 cp` simply copies the specified files/directories without checking if they already exist in the destination or if they are up-to-date.
- Example:
- Copy a single file to S3: aws s3 cp mylocalfile.txt s3://mybucket/
- Copy a directory to S3 recursively: aws s3 cp mylocaldirectory s3://mybucket/ --recursive
2. `aws s3 sync` (Synchronize):
- The `aws s3 sync` command is designed to synchronize a directory with an S3 bucket. It intelligently updates the destination by only copying new or modified files.
- It compares the source and destination directories or buckets, copying files that are new or have been modified, and optionally deleting files from the destination if they no longer exist in the source (using the --delete flag).
- The synchronization happens recursively, meaning it processes all subdirectories as well.
- It's optimized for maintaining an up-to-date replica of a local directory on S3 or vice-versa.
- `aws s3 sync` can significantly reduce bandwidth and processing time compared to repeatedly copying the entire directory using aws s3 cp --recursive.
- Example:
- Synchronize a local directory with an S3 bucket: aws s3 sync mylocaldirectory s3://mybucket/
- Synchronize and delete extra files in the destination: aws s3 sync mylocaldirectory s3://mybucket/ --delete
Key Differences Summarized:
- Functionality: cp is for straightforward copying, while sync is for intelligent synchronization.
- Efficiency: sync is generally more efficient for keeping directories up-to-date, as it only transfers the necessary files.
- Recursion: cp requires the --recursive flag for directory copying, whereas sync is inherently recursive.
- Deletion: sync can delete files in the destination that are not in the source (using the --delete flag), while cp does not have this capability.
- Use Cases: Use cp for simple file/directory copies or when you want to overwrite the destination. Use sync to keep a directory synchronized with an S3 bucket or another directory efficiently.
In essence, if you want to make sure your S3 Bucket mirrors your local directory, you should use aws s3 sync. If you just want to copy something quickly and easily, without worrying about deletion of old files, you should use aws s3 cp.