From 3e188238d08ce0090b2affa150f25210c42b219e Mon Sep 17 00:00:00 2001
From: Erik Arvstedt <erik.arvstedt@gmail.com>
Date: Tue, 7 Apr 2020 23:05:09 +0200
Subject: [PATCH] only update bitcoin.conf when changed

---
 modules/bitcoind.nix | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/modules/bitcoind.nix b/modules/bitcoind.nix
index d334ec1..2588559 100644
--- a/modules/bitcoind.nix
+++ b/modules/bitcoind.nix
@@ -253,12 +253,14 @@ in {
         if [[ ! -e ${cfg.dataDir}/blocks ]]; then
           mkdir -m 0770 -p '${cfg.dataDir}/blocks'
         fi
+        chown -R '${cfg.user}:${cfg.group}' '${cfg.dataDir}'
         chmod -R g+rX '${cfg.dataDir}/blocks'
 
-        cp '${configFile}' '${cfg.dataDir}/bitcoin.conf'
-        chmod o-rw  '${cfg.dataDir}/bitcoin.conf'
-        chown -R '${cfg.user}:${cfg.group}' '${cfg.dataDir}'
-        echo "rpcpassword=$(cat ${config.nix-bitcoin.secretsDir}/bitcoin-rpcpassword)" >> '${cfg.dataDir}/bitcoin.conf'
+        cfg=$(cat ${configFile}; printf "rpcpassword="; cat "${config.nix-bitcoin.secretsDir}/bitcoin-rpcpassword")
+        confFile='${cfg.dataDir}/bitcoin.conf'
+        if [[ ! -e $confFile || $cfg != $(cat $confFile) ]]; then
+          install -o '${cfg.user}' -g '${cfg.group}' -m 640  <(echo "$cfg") $confFile
+        fi
       '';
       # Wait until RPC port is open. This usually takes just a few ms.
       postStart = ''