Restore AWS glacier data created with synology hyper backup

Solution 1:

So the problem was that there were numerous files in subfolders which I overlooked. Using AWS cli I could finally "init restore" all of them. Afterwards Synology's Hyper Backup restoration worked normally. Here the commands to

restore all files from Glacier back to S3 using aws cli:

# create a text file with all glacier files:
aws s3api list-objects-v2 \
  --bucket my-bucket \
  --query "Contents[?StorageClass=='DEEP_ARCHIVE']" \
  --output text  | awk '{print substr($0, index($0, $2))}' | awk '{NF-=3};3' > filelist_of_glacier_files.txt

# init restore on all files in that filelist:
while read filename; do \
  aws s3api restore-object \
     --bucket my-bucket --key $filename \
     --restore-request '{"Days":25,"GlacierJobParameters":{"Tier":"Standard"}}' ; 
done < filelist_of_glacier_files.txt

Afterwards, Synology's Hyper-Backup "restore" will work normally (after waiting for ~24 hours until glacier restore completed)