How do I restore from AWS Glacier back to S3 permanently?

To provide a complete answer I've combined two other SO posts:

Step one temporarily restore everything:

1. Get a listing of all GLACIER files (keys) in the bucket (you can skip this step if you are sure all files are in Glacier).

   aws s3api list-objects-v2 --bucket <bucketName> --query "Contents[?StorageClass=='GLACIER']" --output text | awk -F '\t' '{print $2}' > glacier-restore.txt

2. Create a shell script and run it, replacing your "bucketName".

   #!/bin/sh
   
   IFS=$'\n'
   for x in `cat glacier-restore.txt`
     do
       echo "Begin restoring ${x}"
       aws s3api restore-object --restore-request Days=7 --bucket <bucketName> --key "${x}"
       echo "Done restoring ${x}"
     done
   

Credit Josh & @domenic-d.

Step two for permanent restore:

aws s3 cp s3://mybucket s3://mybucket --force-glacier-transfer --storage-class

done and done.

Credit to @pete-dermott's comment here.

I used the following command to restore S3 object from the Amazon Glacier storage class :

aws s3api restore-object --bucket bucket_name --key dir1/sample.obj --restore-request '{"Days":25,"GlacierJobParameters":{"Tier":"Standard"}}'

Here a temporary copy of the object is made available for the duration specified in the restore request, such as the 25 days used in the above command.

If the JSON syntax used in the example results in an error on a Windows client, replace the restore request with the following syntax:

--restore-request Days=25,GlacierJobParameters={"Tier"="Standard"}

Note: This will only create a temporary copy of the object for the specified duration.You have to make use of the copy operation to overwrite the object as a Standard object.

To change the object's storage class to Amazon S3 Standard use the following command:

aws s3 cp s3://bucket_name/dir1 s3://bucket_name/dir1 --storage-class STANDARD --recursive --force-glacier-transfer

This will recursively copy and overwrite existing objects with the Amazon S3 Standard storage class.

You don't need a new bucket. You restore the objects from glacier (temporarily) and then overwrite them using the COPY operation, which essentially creates new objects and they'll stay around. Needless to say, you'll need to disable your aging-away-to-glacier lifecycle.

Temporary restore:

aws s3api restore-object --restore-request Days=7 --bucket <bucketName> --key <keyName>

Replace with copied object:

aws s3 cp s3://bucketName/keyName s3://bucketName/keyName --force-glacier-transfer --storage-class STANDARD

Docs say:

The transition of objects to the GLACIER storage class is one-way.

You cannot use a lifecycle configuration rule to convert the storage class of an object from GLACIER to STANDARD or REDUCED_REDUNDANCY storage classes. If you want to change the storage class of an archived object to either STANDARD or REDUCED_REDUNDANCY, you must use the restore operation to make a temporary copy first. Then use the copy operation to overwrite the object as a STANDARD, STANDARD_IA, ONEZONE_IA, or REDUCED_REDUNDANCY object.

Ref.

...going back to Glacier

Being pedantic for a moment, the archived objects aren't moving between s3 and glacier, they're permanently in glacier and temporary copies are made in S3 - It's important to note that you're paying for both glacier and s3 when you temporarily restore them. Once your retention period expires, the S3 copies are deleted.