daemons and daemon users (specifically transmission-daemon) on OS X 10.5.8

Question

I'm trying to set up transmission-daemon on a box running Mac OS 10.5.8. I want to do things the right way, which means (to my understanding)

1. create a service user (_transmission, for example) for the program to run under
2. create a launchd UserAgent .plist to run transmission-daemon at system start-up, and to keep it running
3. configure transmission-daemon

I think I've done step 1 correctly. I used dscl and referenced this question on serverfault to create a user called _transmission. Here's my setup:

$ dscl . -read /Users/_transmission
 AppleMetaNodeLocation: /Local/Default
 GeneratedUID: 31D12B9E-EA47-4595-BFC4-57EB232C3B33
 NFSHomeDirectory: /var/transmission
 Password: *
 PrimaryGroupID: 1001
 RealName:
  Transmission bittorrent daemon
 RecordName: _transmission
 RecordType: dsRecTypeStandard:Users
 UniqueID: 1001
 UserShell: /usr/bin/false

That seems OK. However, I can't get my launchd UserAgent to run the daemon. Here's my attempt at a .plist. Transmission doesn't run after I call launchctl load -w /Library/LaunchAgents/com.transmissionbt.transmission-daemon

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
"http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>EnvironmentVariables</key>
<dict>
    <key>TRANSMISSION_WEB_HOME</key>
    <string>/var/transmission/Web</string>
</dict>
<key>Label</key>
<string>com.transmissionbt.transmission-daemon</string>
<key>OnDemand</key>
<false/>
<key>Program</key>
<string>/usr/sbin/transmission-daemon</string>
<key>ProgramArguments</key>
<array>
    <string>transmission-daemon</string>
    <string>-f</string>
</array>
<key>RunAtLoad</key>
<true/>
<key>ServiceDescription</key>
<string>Transmission-Daemon bittorrent client</string>
<key>UserName</key>
<string>_transmission</string>
</dict>
</plist>

So my question is two-fold:

1. What is the best way to create daemon service users on OS X?
2. Why isn't my launchd LaunchAgent .plist working?

Answer 1

This is just a guess, but according to the manpage "UserName " is only applicable when launchd is running as root.

try unloading the plist if it's already running:

launchctl unload /Library/LaunchAgents/com.transmissionbt.transmission-daemon

and then run as root:

sudo launchctl load -w /Library/LaunchAgents/com.transmissionbt.transmission-daemon

Can you confirm that it actually loads:

launchctl list | grep transmissionbt

Let me know if this works out for ya.