This read-write string is a control object: setting it to a package name triggers the gateway to initiate an UNPACK operation for that already-downloaded package, the phase tracked by unpackStatus. Admins use this to explicitly advance a package through the deployment lifecycle once its download has completed, rather than relying on any automatic progression. For example, after downloadStatus confirms a package finished downloading, an admin would SET unpackCommand to that same package's name to begin extracting it, which unpackStatus would then reflect as it proceeds.