fd-usage is available on Linux only

diff --git a/pdns/recursordist/docs/metrics.rst b/pdns/recursordist/docs/metrics.rst
index f8993129cf3204f554e903f8efa4c627826c8e64..64fad908dec7fae8b8f44168b859e7dfca020d01 100644 (file)
--- a/pdns/recursordist/docs/metrics.rst
+++ b/pdns/recursordist/docs/metrics.rst
@@ -490,6 +490,7 @@ number of servers that failed to resolve
 fd-usage
 ^^^^^^^^
 Number of currently used file descriptors.
+This metric is available on Linux only.
 
 ignored-packets
 ^^^^^^^^^^^^^^^