nbdkit is a really powerful NBD toolkit.

Lately, i wanted to access VM backups from a Proxmox Backup Server via network (not by using the proxmox-backup-client map function..)

For example, to test-boot a virtual machine snapshot directly from a backup. NBD suits that usecase quite well, so i quickly put a nbdkit plugin together that can be used for this.

The available golang bindings for the proxmox backup client API, made that quite easy.

As nbdkit already comes with a neat COW plugin, its only been a few lines of go code resulting in: pbsnbd