update readme

Signed-off-by: Victor Vieux <victorvieux@gmail.com>

Author: vieux

README.md

@@ -7,6 +7,8 @@ This plugin allows you to mount remote folder using sshfs in your container easi
 
 ## Usage
 
+### Using a password
+
 1 - Install the plugin
 
 ```
@@ -40,6 +42,41 @@ vieux/sshfs         sshvolume
 $ docker run -it -v sshvolume:<path> busybox ls <path>
 ```
 
+### Using an ssh key
+
+1 - Install the plugin
+
+```
+$ docker plugin install vieux/sshfs sshkey.source=/home/<user>/.ssh/
+
+# or to enable debug 
+docker plugin install vieux/sshfs DEBUG=1 sshkey.source=/home/<user>/.ssh/
+
+# or to change where plugin state is stored
+docker plugin install vieux/sshfs state.source=<any_folder> sshkey.source=/home/<user>/.ssh/
+```
+
+2 - Create a volume
+
+```
+$ docker volume create -d vieux/sshfs -o sshcmd=<user@host:path> [-o IdentityFile=/root/.ssh/<key>] [-o port=<port>] [-o <any_sshfs_-o_option> ] sshvolume
+sshvolume
+$ docker volume ls
+DRIVER              VOLUME NAME
+local               2d75de358a70ba469ac968ee852efd4234b9118b7722ee26a1c5a90dcaea6751
+local               842a765a9bb11e234642c933b3dfc702dee32b73e0cf7305239436a145b89017
+local               9d72c664cbd20512d4e3d5bb9b39ed11e4a632c386447461d48ed84731e44034
+local               be9632386a2d396d438c9707e261f86fd9f5e72a7319417901d84041c8f14a4d
+local               e1496dfe4fa27b39121e4383d1b16a0a7510f0de89f05b336aab3c0deb4dda0e
+vieux/sshfs         sshvolume
+```
+
+3 - Use the volume
+
+```
+$ docker run -it -v sshvolume:<path> busybox ls <path>
+```
+
 ## LICENSE
 
 MIT