> First Q, are my server successfully started or not?

Your process list's show that postgresql is running on both machines, however no slon daemons are running.

> Q2, I have setup one succeed machine that run both slony
> and postgresql
> correctly. But the above two are not. if I want to start
> slon on these two
> slaves it will say:
> 
> -bash-3.2$ slon sql_cluster "dbname=contactdb
> user=postgres"
> -bash: slon: command not found
> 
> This happen on both of above machines.  Why is that?

Either slony is not installed, or your path is probably not set correctly.

It would appear that most of the issues you're having are with the *nix environment in general, perhaps it'd be an idea to do a bit of reading or get some training there.