Add notes about setting pg_bindir for Debian/Ubuntu-based distributions.

repmgr doesn't know about pg_ctlcluster.

Per GitHub query #196.

README.md

@@ -375,6 +375,16 @@ to include this schema name, e.g.
 
     ALTER USER repmgr SET search_path TO repmgr_test, "$user", public;
 
+* * *
+
+> *TIP*: for Debian-based distributions we recommend explictly setting
+> `pg_bindir` to the directory where `pg_ctl` and other binaries not in
+> the standard path are located. For PostgreSQL 9.5 this would be
+> `/usr/lib/postgresql/9.5/bin/`.
+
+* * *
+
+
 ### Initialise the master server
 
 To enable `repmgr` to support a replication cluster, the master node must

repmgr.conf.sample

@@ -100,6 +100,9 @@
 # path to PostgreSQL binary directory (location of pg_ctl, pg_basebackup etc.)
 # (if not provided, defaults to system $PATH)
 #pg_bindir=/usr/bin/
+#
+# Debian/Ubuntu users: you will probably need to set this to the directory
+# where `pg_ctl` is located, e.g. /usr/lib/postgresql/9.5/bin/
 
 # service control commands
 #