From e18ae48dd6121f7415ebcdfa710ff1597ac3d438 Mon Sep 17 00:00:00 2001
From: Daniel Langbein <daniel@systemli.org>
Date: Mon, 20 Nov 2023 19:12:54 +0100
Subject: [PATCH] yodaHedgehog: WIP backup service

---
 examples/block-opensmtpd-queue.sh    | 12 ++++++++
 hosts/yodaHedgehog/host-specific.nix | 41 +++++++++++++++++++++-------
 2 files changed, 43 insertions(+), 10 deletions(-)
 create mode 100644 examples/block-opensmtpd-queue.sh

diff --git a/examples/block-opensmtpd-queue.sh b/examples/block-opensmtpd-queue.sh
new file mode 100644
index 0000000..59ffbf8
--- /dev/null
+++ b/examples/block-opensmtpd-queue.sh
@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+echo -e "Subject: Test\n\nHi there, this is some test." | sendmail -f langbein@mail.de daniel@systemli.org
+while :; do
+  # Note: smtpctl requires root privileges.
+  queue="$(smtpctl show queue)"
+  if [ "${queue}" = "" ]; then
+    break
+  fi
+  printf '%s\n' 'Delaying suspend due to non-empty smtpd email queue.'
+  sleep 5s
+done
diff --git a/hosts/yodaHedgehog/host-specific.nix b/hosts/yodaHedgehog/host-specific.nix
index 7fee1da..e0f65e8 100644
--- a/hosts/yodaHedgehog/host-specific.nix
+++ b/hosts/yodaHedgehog/host-specific.nix
@@ -9,7 +9,11 @@
 #    2.6W suspended, with 1 RAM, 1 SSD, 2 HDDs
 #   18.9W idle, with 1 RAM, 1 SSD, 2 HDDs
 
-# journalctl -u daily-backup-and-suspend
+# View service log:
+#   journalctl -u daily-backup-and-suspend
+
+# Print unit file:
+#   cat "$(systemctl show -P FragmentPath daily-backup-and-suspend.service)"
 
 { config, pkgs, ... }:
 let
@@ -42,10 +46,12 @@ in
     # Packages required for this script.
     # For `ssh` and `journalwatch`, there are assertions above.
     path = with pkgs; [
-      # Provides `echo`, `sleep`, `printf`.
-      coreutils
       # Provides `ssh`
       openssh
+      # Provides `awk`, `grep`, `sleep`, `printf`, `echo`, 'sendmail'
+      busybox
+      # Provides `smtpctl`
+      opensmtpd
     ];
     # Script to execute as main process.
     script = ''
@@ -56,8 +62,8 @@ in
 
       # Don't suspend as long as `${backup-source}:${stay-awake-file}` exists.
       while :; do
-        result="$(ssh ${backup-source} 'ls ${stay-awake-file} 2>&1')"
-        case "$${result}" in
+        result="$(ssh ${backup-source} 'ls ${stay-awake-file} 2>&1')" ||:
+        case "''${result}" in
           *"No such file or directory")
             break
             ;;
@@ -72,21 +78,36 @@ in
       done
 
       # Wait until no BTRFS scrub service is running.
-      while systemctl list-units --type=service --plain --quiet | awk '{ print $1 }' | grep '^btrfs-scrub'; do
+      while :; do
+        running_services="$(systemctl list-units --type=service --plain --quiet | awk '{ print $1 }')"
+        if ! printf '%s' "''${running_services}" | grep '^btrfs-scrub'; then
+          break;
+        fi
         printf '%s\n' 'Delaying suspend due to running BTRFS scrub service.'
         sleep 60s
       done
 
       # Send filtered journal by email.
       systemctl start journalwatch.service ||:
-      # Short delay to let sendmail send the email.
+      # Send notification by email.
+      printf '%s\n\n%s' 'Subject: ${config.networking.hostName}' 'Finished backup.' | sendmail -f langbein@mail.de daniel@systemli.org
+
+      # Let sendmail send emails.
+      #while :; do
+      #  # TODO: Plain usage of `smtpctl` gives the error:
+      #  #   smtpctl: this program must be setgid smtpq
+      #  queue="$(smtpctl show queue)"
+      #  if [ "''${queue}" = "" ]; then
+      #    break
+      #  fi
+      #  printf '%s\n' 'Delaying suspend due to non-empty smtpd email queue.'
+      #  sleep 1s
+      #done
       sleep 15s
 
       printf '%s\n' 'Finished backup script.'
-
       # Suspend to save power.
-      # TODO
-      #systemctl suspend
+      systemctl suspend
     '';
   };
 }