PRoot is a user-space implementation of "chroot", "mount --bind", and "binfmt_misc". This means that users don't need any privileges or setup to do things like using an arbitrary directory as the new root filesystem, making files accessible somewhere else in the filesystem hierarchy, or executing programs built for another CPU architecture transparently through QEMU user mode. Also, developers can add their own features or use PRoot as a Linux process instrumentation engine thanks to its extension mechanism. Technically, PRoot relies on "ptrace", an unprivileged system call available in every Linux kernel.
qemu-diskp is a FUSE mounter to mount virtual disk images. Most virtual machine environments provide a raw disk model to the operating system(s) they host. Typically this raw disk is stored as a simple file rather than a dedicated hardware device. Since the file is a bit-image of what would normally be an actual hardware disk, it holds a complete disk layout. This makes it difficult to mount or manage each of the filesystems within that virtual disk image by the host machine, especially if the file for the image is itself a composite, such as a qemu qcow2 file. This project provides a FUSE based filesystem that presents each of the partitions in a full disk image as individual files. Those files may then be accessed by user-level applications (e.g. fsck or mke2fs) or loop-back mounted, enabling normal file system tools to examine or modify their contents.