nsmount

nsmount is a utility to mount a path from one process' mount namespace to another process' mount namespace.

It works by:

1. Opening mount namespace file descriptors for both the source and target PIDs via /proc/<pid>/ns/mnt
2. Entering the source namespace using setns() and cloning the mount at from-path using the open_tree syscall
3. Entering the target namespace using setns() and attaching the cloned mount at to-path using the move_mount syscall

Requires Linux 5.2+ due to the use of open_tree and move_mount syscalls.

Usage

	nsmount <from-pid> <from-path> <to-pid> <to-path>