Document -f option of boot

1 files changed, 3 insertions, 1 deletions

diff --git a/hurd/subhurd.mdwn b/hurd/subhurd.mdwn
index 55927fdd..0c7677a9 100644
--- a/hurd/subhurd.mdwn
+++ b/hurd/subhurd.mdwn
@@ -103,7 +103,9 @@ practice [that doesn't work at the
 moment](http://savannah.gnu.org/bugs/?17341).)
 
 You can provide the subhurd with a network card by passing a `-f` option to
-`boot`.
+`boot`.  For instance, if you have a second network card `/dev/eth1` in your
+host hurd, pass `-f eth0=/dev/eth1` to make it appear as device eth0 in the
+subhurd.
 
 Now the subhurd should boot just like a normal Hurd started directly from GRUB,
 finally presenting a login prompt.  The `boot` program serves as proxy for the