Update readme instructions to use specific node/validator counts (fixes #483)

README.md

@@ -112,17 +112,18 @@ The beacon node simulation will create a full peer-to-peer network of beacon nod
 
 ```bash
 # Clear data files from your last run and start the simulation with a new genesis block:
-make eth2_network_simulation
+make VALIDATORS=192 NODES=6 MISSING_NODES=1 eth2_network_simulation
 
 # In another terminal, get a shell with the right environment variables set:
 ./env.sh bash
 
-# Run an extra node - by default the network will launch with 9 nodes, each
-# hosting 10 validators. The last 10 validators are lazy bums that hid from the
-# startup script, but you can command them back to work with:
-./tests/simulation/run_node.sh 9
+# In the above example, the network is prepared for 7 beacon nodes but one of
+# them is not started by default (`MISSING_NODES`) - you can start it separately
+# by running:
+./tests/simulation/run_node.sh 6 # (or the 0-based node number of the missing node)
 
-# (yes, it's 0-based indexing)
+# Running a separate node allows you to test sync as well as see what the action
+# looks like from a single nodes' perspective.
 ```
 
 You can also separate the output from each beacon node in its own panel, using [multitail](http://www.vanheusden.com/multitail/):

tests/simulation/vars.sh

@@ -13,6 +13,8 @@ cd $(git rev-parse --show-toplevel)
 : ${GIT_ROOT:="$($PWD_CMD)"}
 cd - &>/dev/null
 
+# When changing these, also update the readme section on running simulation
+# so that the run_node example is correct!
 NUM_VALIDATORS=${VALIDATORS:-192}
 NUM_NODES=${NODES:-6}
 NUM_MISSING_NODES=${MISSING_NODES:-1}