From 477e22be863cc418bdc73f0bbe8b6dcffb75e6e2 Mon Sep 17 00:00:00 2001
From: Donald Buczek <buczek@molgen.mpg.de>
Date: Thu, 31 Jan 2019 08:15:51 +0100
Subject: [PATCH] serial-log: Do not fail when tty is unavailable

I don't like the fact, that on most systems `systemctl status` shows
the state as degraded and that we have irrelevant entries in the journal,
just because we don't have a functioning ttyS1 available.

Regard serial.log\@ as a "best effort" service, which continuously tries
to work with the device and just waits a bit on failure.

Use an external command for the loop instead of abusing the service
restart feature of systemd for that.
---
 install.sh                     |  1 +
 serial-log/serial-log          | 14 ++++++++++++++
 serial-log/serial-log@.service |  7 ++-----
 3 files changed, 17 insertions(+), 5 deletions(-)
 create mode 100755 serial-log/serial-log

diff --git a/install.sh b/install.sh
index 6daac67..95dc3ef 100755
--- a/install.sh
+++ b/install.sh
@@ -134,4 +134,5 @@ install_exec hostconfig/hostconfig                       "$DESTDIR$usr_sbindir/h
 install_exec fon/fon.sh                                  "$DESTDIR$usr_bindir/fon"
 install_exec nfsdtop/nfsdtop                             "$DESTDIR$usr_sbindir/nfsdtop"
 install_data serial-log/serial-log\@.service             "$DESTDIR$systemdunitdir/serial-log@.service"
+install_exec serial-log/serial-log                       "$DESTDIR$usr_exec_prefix/libexec/serial-log"
 exit
diff --git a/serial-log/serial-log b/serial-log/serial-log
new file mode 100755
index 0000000..21e2b49
--- /dev/null
+++ b/serial-log/serial-log
@@ -0,0 +1,14 @@
+#! /bin/bash
+
+(($#==1)) || { echo "usage: $0 device-name" >&2; exit 1; }
+
+devnam="$1"
+
+while true; do
+	until /usr/bin/stty -F "/dev/$devnam" 115200 -echo 2>/dev/null; do
+		sleep 60
+	done
+	until cat "/dev/$devnam" >> /var/log/$devnam.log 2>&1;do
+		sleep 1
+	done
+done
diff --git a/serial-log/serial-log@.service b/serial-log/serial-log@.service
index 5f0c878..917907c 100644
--- a/serial-log/serial-log@.service
+++ b/serial-log/serial-log@.service
@@ -2,11 +2,8 @@
 Description=TTY logger
 
 [Service]
-ExecStartPre=/usr/bin/stty -F /dev/%I 115200 -echo
-ExecStart=-/usr/bin/sh -c "/usr/bin/cat /dev/%I >> /var/log/%I.log 2>&1"
-Type=idle
-Restart=always
-RestartSec=0
+ExecStart=/usr/libexec/serial-log %I
+Type=simple
 UtmpIdentifier=%I
 
 [Install]