diff --git a/reactor-plc/config.lua b/reactor-plc/config.lua
index dceeb21..43086d5 100644
--- a/reactor-plc/config.lua
+++ b/reactor-plc/config.lua
@@ -6,3 +6,9 @@ REACTOR_ID  = 1
 SERVER_PORT = 16000
 -- port to listen to incoming packets FROM server
 LISTEN_PORT = 14001
+-- log path
+LOG_PATH = "/log.txt"
+-- log mode
+--  0 = APPEND (adds to existing file on start)
+--  1 = NEW (replaces existing file on start)
+LOG_MODE = 0
diff --git a/reactor-plc/startup.lua b/reactor-plc/startup.lua
index 2952191..69038d3 100644
--- a/reactor-plc/startup.lua
+++ b/reactor-plc/startup.lua
@@ -19,7 +19,7 @@ local println = util.println
 local print_ts = util.print_ts
 local println_ts = util.println_ts
 
-log.init("/log.txt", log.MODE.APPEND)
+log.init(config.LOG_PATH, config.LOG_MODE)
 
 log._info("========================================")
 log._info("BOOTING reactor-plc.startup " .. R_PLC_VERSION)
diff --git a/rtu/config.lua b/rtu/config.lua
index 71804a4..6ba5653 100644
--- a/rtu/config.lua
+++ b/rtu/config.lua
@@ -4,6 +4,12 @@
 SERVER_PORT = 16000
 -- port to listen to incoming packets FROM server
 LISTEN_PORT = 15001
+-- log path
+LOG_PATH = "/log.txt"
+-- log mode
+--  0 = APPEND (adds to existing file on start)
+--  1 = NEW (replaces existing file on start)
+LOG_MODE = 0
 -- RTU peripheral devices (named: side/network device name)
 RTU_DEVICES = {
     {
diff --git a/rtu/startup.lua b/rtu/startup.lua
index 6220ad1..59c4354 100644
--- a/rtu/startup.lua
+++ b/rtu/startup.lua
@@ -26,7 +26,7 @@ local println = util.println
 local print_ts = util.print_ts
 local println_ts = util.println_ts
 
-log.init("/log.txt", log.MODE.APPEND)
+log.init(config.LOG_PATH, config.LOG_MODE)
 
 log._info("========================================")
 log._info("BOOTING rtu.startup " .. RTU_VERSION)
diff --git a/supervisor/config.lua b/supervisor/config.lua
index fde20b3..b8ba7fa 100644
--- a/supervisor/config.lua
+++ b/supervisor/config.lua
@@ -4,3 +4,9 @@ SCADA_DEV_LISTEN = 16000
 SCADA_SV_LISTEN = 16100
 -- expected number of reactors
 NUM_REACTORS = 4
+-- log path
+LOG_PATH = "/log.txt"
+-- log mode
+--  0 = APPEND (adds to existing file on start)
+--  1 = NEW (replaces existing file on start)
+LOG_MODE = 0
diff --git a/supervisor/startup.lua b/supervisor/startup.lua
index 9cf704a..946ef0c 100644
--- a/supervisor/startup.lua
+++ b/supervisor/startup.lua
@@ -25,7 +25,7 @@ local println = util.println
 local print_ts = util.print_ts
 local println_ts = util.println_ts
 
-log.init("/log.txt", log.MODE.APPEND)
+log.init(config.LOG_PATH, config.LOG_MODE)
 
 log._info("========================================")
 log._info("BOOTING supervisor.startup " .. SUPERVISOR_VERSION)