(2025-07-14) Taming the daemons, the POSIX way
----------------------------------------------
As you might know, I am also running a fully self-hosted Nex station along
with some additional services on my Orange Pi Zero. The way I'm exposing the 
ports of those services relies on the SSH functionality along with some 
config tweaks on both sides, maybe I'm gonna cover it the other time. For 
now though, I'd like to focus on a different aspect of that setup: service 
management. Of course, I could wrap all the scripts into systemd units but I 
don't think that's portable enough, and I'd have to move those units into a 
place I definitely would forget about at some point. So, up until today, I 
had individual start/stop scripts for each individual service on that 
Orange. But then, I found all of them too similar to each other and thought 
that maybe, just maybe, all my custom daemon management could be ruled from 
a single place. Thus, the DaemonTamer was born.

You can download it from the "Downloads" section of this Gopherhole but here
it is, in its entirety:

#!/bin/sh
# DaemonTamer: simple and portable local service manager in pure sh
# that allows to quickly daemonize any command and manage it as a service
# Depends on POSIX versions of sh, nohup, cut and grep
# the unreg option also depends on mktemp (not POSIX but present everywhere)
# Run sh dt help to see the parameters
# Created by Luxferre in 2025, released into public domain with no warranties

err() {
  echo $*
  exit 1
}

find_service() {
  sline="$(grep -E "^$1\s+" $CONF)"
  [ -z "$sline" ] && err "No such service found in the config!"
  echo "$sline"
}

CONF="$HOME/.dt.conf"
srv_name="$2"
[ "$1" != "help" ] && [ -z "$srv_name" ] && err "Service name is required!"
pidfile="/tmp/$srv_name.pid"
case $1 in
help)
  echo 'DaemonTamer v1'
  echo "Usage: $0 {reg|unreg|start|stop|restart} SERVICE_NAME [REG_PARAMS]"
  echo 'Parameters for the reg subcommand:'
  echo "$0 reg 'COMMAND' [WORKDIR] [STDOUT_LOG_FILE] [STDERR_LOG_FILE]"
  echo '(the COMMAND must be specified in single quotes and without nohup)'
  echo "\nCreated by Luxferre in 2025, released into public domain with no
warranties"
  ;;
reg)
  srv_cmd="$3"
  [ -z "$srv_cmd" ] && err "Service runner command is required!"
  srv_wdir="$4"
  srv_outlog="$5"
  srv_errlog="$6"
  [ -z "$srv_wdir" ] && srv_wdir='none'
  [ -z "$srv_outlog" ] && srv_outlog='/dev/null'
  [ -z "$srv_errlog" ] && srv_errlog='/dev/null'
  printf "%s\t%s\t%s\t%s\t%s\n" "$srv_name" "$srv_cmd" "$srv_wdir" \
    "$srv_outlog" "$srv_errlog" >> $CONF
  echo "Service $srv_name registered"
  ;;
unreg)
  srvline="$(find_service "$srv_name")"
  TCONF="$(mktemp)"
  grep -v "$srv_name" $CONF > $TCONF && mv $TCONF $CONF
  echo "Service $srv_name unregistered"
  ;;
start)
  srvline="$(find_service "$srv_name")"
  srv_cmd="$(echo "$srvline" | cut -f2)"
  srv_wdir="$(echo "$srvline" | cut -f3)"
  srv_outlog="$(echo "$srvline" | cut -f4)"
  srv_errlog="$(echo "$srvline" | cut -f5)"
  echo "Starting service $srv_name"
  echo "- command: $srv_cmd"
  echo "- workdir: $srv_wdir"
  echo "- stdout: $srv_outlog"
  echo "- stderr: $srv_errlog"
  [ "$srv_wdir" != "none" ] && cd "$srv_wdir"
  nohup $srv_cmd >$srv_outlog 2>$srv_errlog & echo $! > $pidfile
  echo "Service $srv_name started"
  ;;
stop)
  srvline="$(find_service "$srv_name")"
  echo "Stopping service $srv_name"
  kill $(cat $pidfile)
  rm -f $pidfile
  echo "Service $srv_name stopped"
  ;;
restart)
  srvline="$(find_service "$srv_name")"
  $SHELL $0 stop $srv_name
  $SHELL $0 start $srv_name
  ;;
*)
  echo 'Invalid operation! Pick start, stop, restart, reg, unreg or help'
  ;;
esac

Yeah, that simple. As you can see, you can register any command in a single
TSV file to be run as a daemon, and you have the options to specify its 
working directory and the files to redirect standard output and error 
streams to. After registering this command, you can also unregister this 
daemon or start/stop/restart it. This is the bare functionality minimum that 
I personally need. Maybe I'll also add some pre/post-start and pre/post-stop 
hooks and some additional checks if the service is already running in v2, 
but that's really it.

The TSV format was intentionally chosen as the simplest one to parse by any
shell-based tool, considering the tab character naturally cannot appear in 
any command, service or file name, and it also is the default one for the 
"cut" command. Bopher-NG vibes, sort of. The only thing I'd like to ask you 
is to not perceive this as any kind of statement. This is a tool created for 
some practical purposes of portability and quick deployment. It can't, won't 
and doesn't aim to replace the main service manager in your OS. If you try 
to do that, don't come yelling at me that something doesn't work. Because it 
probably was never supposed to work the way you expected. In any event, stay 
tuned for v2, you don't want to miss it. Just kidding.

--- Luxferre ---