How to copy file across buckets using aws-s3 or aws-sdk gem in ruby on rails

When using the AWS SDK gem's copy_from or copy_to there are three things that aren't copied by default: ACL, storage class, or server side encryption. You need to specify them as options.

from_object.copy_to from_object.key, {:bucket => 'new-bucket-name', :acl => :public_read}

https://github.com/aws/aws-sdk-ruby/blob/master/lib/aws/s3/s3_object.rb#L904

For anyone still looking, AWS has documentation for this. It's actually very simple with the aws-sdk gem:

bucket = Aws::S3::Bucket.new('source-bucket')
object = bucket.object('source-key')

object.copy_to(bucket: 'target-bucket', key: 'target-key')

Using the right_aws gem:

# With s3 being an S3 object acquired via S3Interface.new
# Copies key1 from bucket b1 to key1_copy in bucket b2:
s3.copy('b1', 'key1', 'b2', 'key1_copy')

the gotcha I ran into is that if you have pics/1234/yourfile.jpg the bucket is only pics and the key is 1234/yourfile.jpg

I got the answer from here: How do I copy files between buckets using s3 from a rails application?

AWS-SDK gem. S3Object#copy_to

Copies data from the current object to another object in S3.
S3 handles the copy so the client does not need to fetch the 
data and upload it again. You can also change the storage 
class and metadata of the object when copying.

It uses copy_object method internal, so the copy functionality allows you to copy objects within or between your S3 buckets, and optionally to replace the metadata associated with the object in the process.

Standard method (download/upload)

Copy method

Code sample:

require 'aws-sdk'

AWS.config(
  :access_key_id     => '***',
  :secret_access_key => '***',
  :max_retries       => 10
)

file     = 'test_file.rb'
bucket_0 = {:name => 'bucket_from', :endpoint => 's3-eu-west-1.amazonaws.com'}
bucket_1 = {:name => 'bucket_to',   :endpoint => 's3.amazonaws.com'}

s3_interface_from = AWS::S3.new(:s3_endpoint => bucket_0[:endpoint])
bucket_from       = s3_interface_from.buckets[bucket_0[:name]]
bucket_from.objects[file].write(open(file))

s3_interface_to   = AWS::S3.new(:s3_endpoint => bucket_1[:endpoint])
bucket_to         = s3_interface_to.buckets[bucket_1[:name]]
bucket_to.objects[file].copy_from(file, {:bucket => bucket_from})