Can't set up witness in Repmgr 2.0
The error message means that repmgr account can't login onto master server with provided password (probably empty one).

You need to allow connections on master, in pg_hba.conf:

host    all     repmgr  192.168.1.1/32       md5
host    replication     all     192.168.1.1/32       md5


then trigger a master server reload:

/usr/lib/postgresql/9.1/bin/pg_ctl reload -D /var/lib/postgresql/9.1/main


(where -D is the data directory of PostgreSQL).

Assumsing you've created a repmgr account, on master with some secret_passw0rd

createuser --login --superuser -P repmgr -W
createdb -O repmgr repmgr


then on standby server create a .pgpass file in postgres home:

su - postgres
cat &gt; .pgpass &lt;&lt; EOF
*:*:*:repmgr:secret_passw0rd
EOF
chmod 0600 .pgpass


That's all under assumption that you're using md5 password authentication for replication, if you switch to trust you could skip setting the password:

host    all     repmgr  192.168.1.1/32       trust
host    replication     all     192.168.1.1/32       trust


Now you can check connection to your master server:

psql -h master.hostname -U repmgr