[launchd-dev] User Deamon

[Dave Zarzycki]

At the moment user-agents cannot be launched at boot. Otherwise the  
solution would be "perfect" (with the exception of FileVault and AFP  
home directories, but that is a different problem). Please file a bug/ 
enhancement-request on that.

I think your configuration file per user is the next best alternative  
in the Leopard timeframe.

Good luck,

davez



On Nov 26, 2007, at 4:20 PM, James Bucanek wrote:

> Welcome,
>
> I was invited to bring this thread here by Quinn. My apologies if  
> you've seen bits and pieced of this thread before; it's traveled  
> around the Cocoa, Carbon, and MacNetworkProg lists before landing  
> here.
>
> I'm developing a backup and document archiving solution (<http://www.qrecall.com/ 
> > -- not an ad, just for reference).
>
> The program provides "actions" that can be scheduled to run at  
> regular intervals or in response to certain events. These actions  
> should be performed whether the user is logged in or out. In fact,  
> actions can be scheduled to run only when the user is logged out or  
> because the user logged out.
>
> There is a scheduler process which is responsible for managing all  
> of this. The scheduler works on behalf of a single user. (Other  
> users may have their own schedule/scheduler.) For security, the  
> scheduler runs under the UID of that user.
>
> So, what I have is a process that
>
> - Needs to start up when the system boots and runs until the system  
> shuts down, independent of whether the user is logged in or not.
>
> - Runs as a single user (not as root) without any special privileges.
>
> - Can be installed and removed without requiring administrative  
> authorization.
>
> In effect, I need a "User Daemon" -- a class of process that launchd  
> does not provide.
>
> I was simulating this (pretty well) using crontab. The crontab will  
> allow non-admin users to install a cronjob that runs periodically  
> and independently of their login session. Unfortunately, recent  
> versions of Tiger and Leopard have become downright hostile towards  
> user cronjobs, sending them SIGKILL signals whenever the user is  
> logged out (without even the courtesy of a SIGTERM first!).
>
> I'm now simulating this by installing a system-wide daemon for each  
> user (/Library/LaunchDaemons/QRecallScheduler501.plist, .../ 
> QRecallScheduler502.plist, etc.). Each daemon is configured to run  
> as that user (via the UserName property). But this requires  
> administrative privileges to install/uninstall a non-privileged  
> process. Beyond being annoying, it limits the usefulness of the  
> application for non-admin users. And in the pit of my stomach, I  
> feel that it presents a security hole.
>
> I'm basically just throwing this out to the launchd team for  
> comments, which might result in filing a feature request.
>
> I also understand some of the potential problems in implementing  
> user daemons. (For example, the logical place to place a user daemon  
> configuration file would be in ~/Library/LaunchDaemons, but that  
> obviously won't work with FileVault or users who mount their home  
> folder over a network.) However, there are also potential solutions  
> to some of these and there's also the principle that one shouldn't  
> necessarily eliminate a feature just because 0.1% of the users can't  
> use it. ;)
>
> Any thoughts?
>
> -- 
> James Bucanek
>
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