From d60f3cf6e9c904912199ea64156fea295494430a Mon Sep 17 00:00:00 2001
From: Florian Klink <flokli@flokli.de>
Date: Thu, 17 Mar 2022 22:59:43 +0100
Subject: [PATCH 1/2] nix-daemon.conf.in: add tmpfiles file to create
 nix/daemon-socket directory

nix-daemon.socket is used to socket-activate nix-daemon.service when
/nix/var/nix/daemon-socket/socket is accessed.

In container usecases, sometimes /nix/var/nix/daemon-socket is
bind-mounted read-only into the container.

In these cases, we want to skip starting nix-daemon.socket.

However, since systemd 250, `ConditionPathIsReadWrite` is also not met
if /nix/var/nix/daemon-socket doesn't exist at all. This means, a
regular NixOS system will skip starting nix-daemon.socket:

> [  237.187747] systemd[1]: Nix Daemon Socket was skipped because of a failed condition check (ConditionPathIsReadWrite=/nix/var/nix/daemon-socket).

To prevent this from happening, ship a tmpfiles file that'll cause the
directory to be created if it doesn't exist already.

In the case of NixOS, we can just add Nix to `systemd.tmpfiles.packages`
and have these files picked up automatically.
---
 misc/systemd/local.mk           | 3 ++-
 misc/systemd/nix-daemon.conf.in | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)
 create mode 100644 misc/systemd/nix-daemon.conf.in

diff --git a/misc/systemd/local.mk b/misc/systemd/local.mk
index 1fa037485..76121a0f9 100644
--- a/misc/systemd/local.mk
+++ b/misc/systemd/local.mk
@@ -1,7 +1,8 @@
 ifdef HOST_LINUX
 
   $(foreach n, nix-daemon.socket nix-daemon.service, $(eval $(call install-file-in, $(d)/$(n), $(prefix)/lib/systemd/system, 0644)))
+  $(foreach n, nix-daemon.conf, $(eval $(call install-file-in, $(d)/$(n), $(prefix)/lib/tmpfiles.d, 0644)))
 
-  clean-files += $(d)/nix-daemon.socket $(d)/nix-daemon.service
+  clean-files += $(d)/nix-daemon.socket $(d)/nix-daemon.service $(d)/nix-daemon.conf
 
 endif
diff --git a/misc/systemd/nix-daemon.conf.in b/misc/systemd/nix-daemon.conf.in
new file mode 100644
index 000000000..e7b264234
--- /dev/null
+++ b/misc/systemd/nix-daemon.conf.in
@@ -0,0 +1 @@
+d @localstatedir@/nix/daemon-socket 0755 root root - -

From 67af5f7eda1dade544cc15397a7d0d35d0913cb2 Mon Sep 17 00:00:00 2001
From: Florian Klink <flokli@flokli.de>
Date: Tue, 22 Mar 2022 17:06:09 +0100
Subject: [PATCH 2/2] scripts/install-systemd-multi-user.sh: install
 /etc/tmpfiles.d/nix-daemon.conf, too

While `create_directories()` from install-multi-user.sh seems to already
create parts of the directory structure, it's marked as deprecated, and
it won't hurt also copying over the tmpfiles config and have it execute
once.
---
 scripts/install-systemd-multi-user.sh | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/scripts/install-systemd-multi-user.sh b/scripts/install-systemd-multi-user.sh
index f4a2dfc5d..24884a023 100755
--- a/scripts/install-systemd-multi-user.sh
+++ b/scripts/install-systemd-multi-user.sh
@@ -9,6 +9,8 @@ readonly SERVICE_DEST=/etc/systemd/system/nix-daemon.service
 readonly SOCKET_SRC=/lib/systemd/system/nix-daemon.socket
 readonly SOCKET_DEST=/etc/systemd/system/nix-daemon.socket
 
+readonly TMPFILES_SRC=/lib/tmpfiles.d/nix-daemon.conf
+readonly TMPFILES_DEST=/etc/tmpfiles.d/nix-daemon.conf
 
 # Path for the systemd override unit file to contain the proxy settings
 readonly SERVICE_OVERRIDE=${SERVICE_DEST}.d/override.conf
@@ -83,6 +85,13 @@ EOF
 poly_configure_nix_daemon_service() {
     if [ -e /run/systemd/system ]; then
         task "Setting up the nix-daemon systemd service"
+
+        _sudo "to create the nix-daemon tmpfiles config" \
+              ln -sfn /nix/var/nix/profiles/default/$TMPFILES_SRC $TMPFILES_DEST
+
+        _sudo "to run systemd-tmpfiles once to pick that path up" \
+             sytemd-tmpfiles create --prefix=/nix/var/nix
+
         _sudo "to set up the nix-daemon service" \
               systemctl link "/nix/var/nix/profiles/default$SERVICE_SRC"