Which command would copy all the files from one S3 bucket to another?

In the context of AWS, to copy all the directories and also the subdirectories from one S3 bucket to another, you can use the following AWS CLI command:-

Aws s3 cp s3://source-bucket s3://destination-bucket –recursive

Recursive functionality

The recursive flag in the command would help you ensure that the AWS CLI would traverse all the directories within the source bucket and copy all the files and subdirectories to the destination Bucket. Without this flag, only the objects at the root level of the sources bucket would be copied. Here is the example scenario given:-

Source bucket structure
Source-bucket/
├── file1.txt
├── dir1/
│   ├── file2.txt
│   └── dir2/
│       └── file3.txt
└── dir3/
    └── file4.txt
Commands implementation
Aws s3 cp s3://source-bucket s3://destination-bucket –recursive
Destination Bucket structure after the command
Destination-bucket/
├── file1.txt
├── dir1/
│   ├── file2.txt
│   └── dir2/
│       └── file3.txt
└── dir3/
    └── file4.txt

Potential issues and solutions

Permission issue

You should try to ensure that the IAM role or user implementing the command should has the necessary permission. The required permissions includes:-

{
  “Version”: “2012-10-17”,
  “Statement”: [
    {
      “Effect”: “Allow”,
      “Action”: [
        “s3:ListBucket”,
        “s3:GetObject”,
        “s3:PutObject”
      ],
      “Resource”: [
        “arn:aws:s3:::source-bucket”,
        “arn:aws:s3:::source-bucket/*”,
        “arn:aws:s3:::destination-bucket”,
        “arn:aws:s3:::destination-bucket/*”
      ]
    }
  ]
}

Large data transfer

For a large bucket, you can consider using the AWS S3 transfer acceleration to handle large files effectively.

Aws s3 sync s3://source-bucket s3://destination-bucket

Bucket policies and ACLs

You should try to ensure that the bucket policies and ACLs for the destination Bucket should be configured to accept the object being copied from the source bucket.

{
  “Version”: “2012-10-17”,
  “Statement”: [
    {
      “Effect”: “Allow”,
      “Principal”: “*”,
      “Action”: [
        “s3:PutObject”
      ],
      “Resource”: [
        “arn:aws:s3:::destination-bucket/*”
      ]
    }
  ]
}

Networks issues

For stable and effective transfer, you can consider trying to run the AWS CLI command from an EC2 Instance within the same AWS region as the S3 buckets. This would help you reduce the latency and would improve the transfer speed.

Aws s3 cp s3://source-bucket s3://destination-bucket –recursive

By carefully considering these details, you can ensure a smooth and efficient operation when you are trying to copy the data between S3 buckets.