const USAGE: &str = "\
Usage:
proot [option] ... [command]
Regular options:
-r *path*, --rootfs=*path* Use *path* as the new guest root file-system, default is /.
-b *path*, --bind=*path* Make the content of *path* accessible in the guest rootfs (host:guest).
-w *path*, --cwd=*path* Set the initial working directory to *path*.
--kill-on-exit Kill all processes on command exit (always on; accepted for compatibility).
-v *value*, --verbose=*value* Set the level of debug information to *value*.
-V, --version Print version, copyright, license and contact, then exit.
-h, --help Print the version and the command-line usage, then exit.
Extension options:
-k *string*, --kernel-release=*string* Make current kernel appear as kernel release *string*.
-0, --root-id Make current user appear as \"root\": ids read as 0, ownership changes succeed.
-l, --link2symlink Accepted and ignored.
Alias options:
-R *path* Alias: -r *path* + a couple of recommended -b.
-S *path* Alias: -0 -r *path* + a couple of recommended -b.
Environment: PROOT_THREADS (default 4) and PROOT_SPIN_US (default 200) tune the supervisor pool;
PROOT_NO_PTRACE=1 forces the mode used where ptrace is filtered out; PROOT_USERNS=1 forces, and
PROOT_USERNS=0 rules out, the user namespace used where Yama's ptrace_scope is 2; where neither
works the guest-stub mode is the fallback (x86_64 and aarch64 hosts), which PROOT_GUEST_STUB=0
rules out and PROOT_GUEST_STUB=force takes anywhere.
";