ssh: The authenticity of host 'hostname' can't be established

Question

When i ssh to a machine, sometime i get this error warning and it prompts to say \"yes\" or \"no\". This cause some trouble when running from scripts that automatically ssh

Answer 1

I had the same error and wanted to draw attention to the fact that - as it just happened to me - you might just have wrong privileges.
You've set up your .ssh directory as either regular or root user and thus you need to be the correct user. When this error appeared, I was root but I configured .ssh as regular user. Exiting root fixed it.