add some note about the ssh-agent

README.md

@@ -13,3 +13,16 @@ Add `--check` to do a dry run
 `ansible-vault edit group_vars/all/vault`
 
 with the edditor defined in the env varible `$EDITOR` and the password of the vault in the file `.vault_password` (Carefull not to commit it!!!)
+
+## SSH key whith passphrase
+
+To avoid entering the passphrase of the ssh key for each host, we have to use an ssh-agent.
+The ssh-agent with xonsh does not really works, so in my case I have to use ansible and the agent inside a sh process:
+
+```
+sh
+eval `ssh-agent -s`
+ssh-add
+ansible all -m ping # or whatever you want to do with ansible
+exit
+```