Copy a large file from a remote host to S3 without a local disk copy: ssh cat | aws s3 cp - with --expected-size

When the remote host has no AWS CLI or credentials and the local machine is short on disk, stream it instead:

ssh host "ionice -c3 nice -n19 cat /path/file" | aws s3 cp - s3://bucket/key --expected-size BYTES --only-show-errors

Notes: - 'aws s3 cp -' reads from stdin. For streams over ~50 GB, pass --expected-size (bytes, an upper bound is fine) so the CLI picks a multipart chunk size that stays under the 10,000-part limit. It is harmless for small files. - Get the sha256 on the remote side first (ssh host sha256sum /path/file) and compare sizes afterwards with aws s3 ls. A stdin upload doesn't store a content hash you can check against later. - On a shared host that is running benchmarks, use ionice -c3 plus nice and taskset onto non-benchmark cores, and check for any timing lock before each file. - Upload one file at a time. Several aws CLI processes running at once against an SSO login can corrupt the shared credential cache. - If your agent's shell refuses complex one-liners (old bash, nested quoting), put the loop in a small script file and run that.