README: clarify runtime and buildtime requirements

As discussed in !86.

Signed-off-by: Yann Dirson <yann.dirson@vates.tech>

diff --git a/README.md b/README.md
index 28387f3415e611f2216178665df55c5a4a37d05f..b426ad9de72a95c983db1fc3dd6b57838b8594e3 100644 (file)
--- a/README.md
+++ b/README.md
@@ -38,6 +38,21 @@ Some features to consider (from `xe-guest-utilities`):
 
 ## Rust prototype
 
+### Runtime requirements
+
+The agent will fail to start if it cannot write the collected info to
+Xenstore, so will only run in a Xen guest.
+
+When built without `-F static`, the agent depends on the availability
+of `libxenstore3.so` or `libxenstore4.so` (probed and loaded at
+runtime).  This library can be found in the `libxenstore3` or
+`libxenstore4` package on Debian-based Linux distros, and in
+`xen-tools` in FreeBSD ports.
+
+When built with Netlink support on FreeBSD, the resulting binary will
+only work when the `netlink` module is loaded (check with `kldstat`,
+load with `kldload netlink`).
+
 ### Build requirements
 
 You need a Rust 1.77 toolchain or later.
@@ -55,8 +70,9 @@ have to install manually on your build machine:
 - pkg-config (on FreeBSD, provided by `pkgconf`)
 - packages needed to build a crate linking against a native lib
   (`llvm-dev` and `clang` on Debian-based Linux distros)
-- development files for libxenstore (package `libxen-dev` on
-  Debian-based Linux distros, `xen-tools` on FreeBSD)
+- building as a static binary requires development files for
+  libxenstore (package `libxen-dev` on Debian-based Linux distros,
+  `xen-tools` on FreeBSD)
 
 ### How to build