From 4f29cf1a1d906f35054f8b318df7c0d3a9117bb3 Mon Sep 17 00:00:00 2001
From: Martin Schwaighofer <mschwaig@users.noreply.github.com>
Date: Thu, 7 Apr 2022 11:28:20 +0200
Subject: [PATCH] installer: ask for confirmation on multi-user install without
 systemd

On Linux a user can go through all the way through the multi-user install
and find out at the end that they now have to manually configure their
init system to launch the nix daemon.

I suspect that for a significant number of users this is not
what they wanted. They might prefer a single-user install.
Now they have to manually uninstall nix before they can
go through the single-user install.

This introduces a confirmation dialog before the install
in that specific situation to make sure that they want to proceed.

See also: https://github.com/NixOS/nix/issues/4999#issuecomment-1064188080
This closes #4999 but rejecting it and closing that issue anyways
would also be valid.
---
 scripts/install-multi-user.sh | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/scripts/install-multi-user.sh b/scripts/install-multi-user.sh
index 69b6676ea..b79a9c23a 100644
--- a/scripts/install-multi-user.sh
+++ b/scripts/install-multi-user.sh
@@ -423,6 +423,18 @@ EOF
         fi
     done
 
+    if [ "$(uname -s)" = "Linux" ] && [ ! -e /run/systemd/system ]; then
+        warning <<EOF
+We did not detect systemd on your system. With a multi-user install
+without systemd you will have to manually configure your init system to
+launch the Nix daemon after installation.
+EOF
+        if ! ui_confirm "Do you want to proceed with a multi-user installation?"; then
+            failure <<EOF
+You have aborted the installation.
+EOF
+        fi
+    fi
 }
 
 setup_report() {