From 78b1ed13e10dc15a542091e28db040c384f1c70b Mon Sep 17 00:00:00 2001
From: Jonas Wagner <boom@confuflux.com>
Date: Thu, 2 Jan 2025 10:39:11 +0100
Subject: [PATCH] something new: 2025-01-02 10:39:11

---
 gist/runbook - ubuntu dist-upgrade.md | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/gist/runbook - ubuntu dist-upgrade.md b/gist/runbook - ubuntu dist-upgrade.md
index 1f2db95..ee6f975 100644
--- a/gist/runbook - ubuntu dist-upgrade.md	
+++ b/gist/runbook - ubuntu dist-upgrade.md	
@@ -1,6 +1,6 @@
 ---
 date created: Friday, December 27th 2024, 4:34:01 pm
-date modified: Monday, December 30th 2024, 10:25:14 am
+date modified: Thursday, January 2nd 2025, 10:38:19 am
 tags: 
 ---
 
@@ -14,6 +14,25 @@ upgrading ubuntu and managing configuration file changes, you might also want to
 DEBIAN_FRONTEND=noninteractive do-release-upgrade --frontend=DistUpgradeViewNonInteractive
 ```
 
+for a truly silent or unattended upgrade, you need to configure `dpkg` to handle changes in configuration files between versions:
+
+```shell
+sh -c 'cat > /etc/apt/apt.conf.d/90force-conf <<EOF
+Dpkg::Options {
+    "--force-confdef";
+    "--force-confold";
+}
+EOF'
+```
+
+explanation from the [dpkg man page](https://manpages.debian.org/buster/dpkg/dpkg.1#OPTIONS):
+
+```
+confold: If a conffile has been modified and the version in the package did change, always keep the old version without prompting, unless the --force-confdef is also specified, in which case the default action is preferred.
+
+confdef: If a conffile has been modified and the version in the package did change, always choose the default action without prompting. If there is no default action it will stop to ask the user unless --force-confnew or --force-confold is also been given, in which case it will use that to decide the final action.
+```
+
 ## post-upgrade: manage configuration file changes
 
 ### locate all changed configuration files