A few hundred ways to backup maybe. Each has some issues good and bad.
General ways. You shouldn't need any sort of file by file copy. Almost any backup plan can dig into some compressed format and retrieve a file.
Backup to a single compressed file. Modern linux can usually dig into the file and get single or groups of files back.
Clone image of disk or partitions. Again linux can mount those images.
Backup only files that you select by schema on.
Could go wild with an isci target deal and rsync it all.
From ubuntu pages. https://help.ubuntu.com/community/BackupYourSystem
Forgot clonezilla and commercial tools like Acronis.
As to why NAS isn't "found", you'd have to explain more. How does linux find it?