added Boot2Docker instructions, and simplified the message when ethtool is missing

README.md

@@ -236,6 +236,27 @@ signal, e.g.
 
 and then inspect the logs.
 
+## Installation with Boot2Docker
+
+If you are running Docker inside the Boot2Docker VM, e.g. because you are 
+on a Mac, then the following changes are required to these instructions:
+
+Assuming you have fetched the 'weave' script via curl or similar, and it 
+is in the current directory, transfer it to the Boot2Docker VM and make it 
+executable like this:
+
+    host1$ boot2docker ssh "cat > weave" < weave
+    host1$ boot2docker ssh "chmod a+x weave"
+
+Then, if we were trying to create the same containers as in the first example 
+above, the launch command would be run like this:
+
+    host1$ WEAVE=$(boot2docker ssh "sudo ./weave launch 10.0.0.1/16")
+
+and the run command like this:
+
+    host1# C=$(boot2docker ssh "sudo ./weave run 10.0.1.1/24 -t -i debian /bin/bash")
+
 ## Building
 
 (NB. This is only necessary if you want to work on weave. Also, these

weaver/weave

@@ -91,7 +91,7 @@ if [ command -v ethtool >/dev/null 2>&1 ]
 then
     ip netns exec $NSPID ethtool -K $IFACE tx off > /dev/null
 else
-    echo "Unable to run ethtool command; continuing without it" >&2
+    echo "Cannot find ethtool; continuing without it" >&2
 fi
 
 [ -f /var/run/netns/$NSPID ] && rm -f /var/run/netns/$NSPID