Two reasons, when making the pid dynamic, restart behavior might get flaky and the usual directory is /var/run and not exposed via the webserver.

@AdSchellevis
This is not my choice. It's defined in file /usr/local/etc/rc.d/xymon-client from the package itself.

Excerpt:

#!/bin/sh

# PROVIDE: xymon_client
# REQUIRE: DAEMON
# KEYWORD: shutdown

. /etc/rc.subr

name=xymon_client
rcvar=xymon_client_enable

load_rc_config "$name"
: ${xymon_client_enable:=NO}
: ${xymon_client_user:=xymon}

pidfile="/usr/local/www/xymon/client/logs/clientlaunch.`hostname`.pid"
command=/usr/local/www/xymon/client/bin/xymonlaunch
command_args="--config=/usr/local/www/xymon/client/etc/clientlaunch.cfg --log=/usr/local/www/xymon/client/logs/clientlaunch.log --pidfile=${pidfile}"
start_precmd=xymon_precmd

[…]

The variable pidfile is not overridable as it uses = and not something like : ${pidfile:=...}

we can change the port rc.d script to better handle an external pid. Eventually we need to do something about the FreeBSD port itself though.

Ok, done see latest commit and PR opnsense/ports#206

when possible, I would prevent saving settings in the www directory, the post install script can be avoided by shipping the xymonclient.cfg for this plugin and using the template directory to flush it to disk (probably in stead of /usr/local/etc/xymon/xymonclient.cfg further below)

@AdSchellevis like https://github.com/opnsense/plugins/pull/4260/files#r1835329433

I don't think this would be possible. The file /usr/local/www/xymon/client/etc/xymonclient.cfg is statically coded from file /usr/local/www/xymon/client/etc/clientlaunch.cfg

# cat /usr/local/www/xymon/client/etc/clientlaunch.cfg
#
# The clientlaunch.cfg file is loaded by "xymonlaunch".
# It controls which of the Xymon client-side modules to run, 
# (both the main client "xymonclient.sh" and any client-side
# extensions); how often, and with which parameters, options 
# and environment variables.
#
# Note: On the Xymon *server* itself, this file is normally 
#       NOT used. Instead, both the client- and server-tasks
#       are controlled by the tasks.cfg file.
#

# msgcache is used for passive clients, that cannot connect
# directly to the Xymon server. This is not the default
# setup, so this task is normally disabled.
[msgcache]
	DISABLED
	ENVFILE $XYMONCLIENTHOME/etc/xymonclient.cfg
	CMD $XYMONCLIENTHOME/bin/msgcache --no-daemon --pidfile=$XYMONCLIENTLOGS/msgcache.pid
	LOGFILE $XYMONCLIENTLOGS/msgcache.log

# The main client task
[client]
	ENVFILE $XYMONCLIENTHOME/etc/xymonclient.cfg
	CMD $XYMONCLIENTHOME/bin/xymonclient.sh 
	LOGFILE $XYMONCLIENTLOGS/xymonclient.log
	INTERVAL 5m

Which is called by the /usr/local/etc/rc.d/xymon-client from the non-overridable variable command_args="--config=/usr/local/www/xymon/client/etc/clientlaunch.cfg --log=/usr/local/www/xymon/client/logs/clientlaunch.log --pidfil e=${pidfile}"

Were you suggesting to completely overwrite the /usr/local/etc/rc.d/xymon-client file from the package to pass our own arguments?

I did some tests to override the /usr/local/etc/rc.d/xymon-client and setting pidfile="/var/run/xymonclient.pid" (as suggested here). This is preventing the service to start as /var/run/ is owned by root:wheel and perms are 0755 and the service is started as user xymon which don't have permission there.

EDIT: I circumvented this by patching the "forked" rc file and added the pid file creation and give it proper permission.

Next issue is giving execution bit to the /usr/local/etc/rc.d/xymon-client now managed by the template system :(

Next issue is giving execution bit to the /usr/local/etc/rc.d/xymon-client now managed by the template system :(

Looks like I can't set it to executable

https://github.com/opnsense/core/blob/84437b3812d959a7aca7f1af8d6c528d8683607d/src/opnsense/service/modules/template.py#L287-L289

So I don't know how I can accomplish what you requested with this comment, neither how to change the pidfile path

File removed here in favor of ports update see PR opnsense/ports#206