What's with HAL?

[Ole Juul]

I've been trying to figure out the dance between HAL and UDEV for the last very many hours. Since changing UDEV rules didn't seem to do anything, I just had a hunch that HAL could be getting in the way.

The documentation seems to be confused. In the Ubuntu Wiki I read:

Input Configuration with udev (Ubuntu 10.04)

Starting with Ubuntu 10.04, HAL has been removed and is no longer involved with device configuration. Where possible, configuration is done automatically in the kernel device driver. Manual configuration overrides can be done through udev rules, in /lib/udev/rules.d/.

In a 10.04 installation I see hald in /usr/sbin and 35 hald files in /usr/lib. What gives?

Particularly concerning are the ones labeled storage:

hal-storage-cleanup-all-mountpoints
hal-storage-cleanup-mountpoint
hal-storage-closetray
hal-storage-eject
hal-storage-mount
hal-storage-unmount

[GreyGeek]

Re: What's with HAL?

What you are seeing relates to the hald, the HAL deamon:

NAME
hald - HAL daemon

SYNOPSIS
hald [options]

DESCRIPTION
hald is a daemon that maintains a database of the devices connected to the system system in real-time. The daemon connects to the D-Bus system message bus to provide an API that applications can use to discover, monitor and invoke operations on devices. For more information about both the big picture and specific API details, refer to the HAL spec which can be found in /usr/share/doc/hal-doc/spec/hal-spec.html depending on the distribution.

From what I understand, most of HAL's chores during bootup are now done by Upstart, or soon will be. If I am wrong there will be some one on this forum who will set us both straight. Upstart is only at 0.6, so it's not even at V 1.0 yet. You can display the System Monitor's Process Table tab and sort on the name. You'll find the nine hald-* services running. Mine show three udev deamons (services) running AND a "upstart-udev-bridge" deamon, which its man page shows:

upstart-udev-bridge(8 ) upstart-udev-bridge(8 )

NAME
upstart-udev-bridge - Bridge between Upstart and udev

SYNOPSIS
upstart-udev-bridge [OPTIONS]...

DESCRIPTION
upstart-udev-bridge receives information about kernel uevents that udev(8 ) has completed and creates init(8 ) events for them.

This is a temporary tool until init(8 ) itself gains the functionality to read them directly; you should not rely on its behaviour.

If you do "man upstart" you be given a manpage for "init(8 )". So, there is a connection. You haven't shown us the rules you are writing so it is hard to say what is "getting in their way".

[claydoh]

Re: What's with HAL?

kde itself still requires hal atm.

I don't know what may have changed in recent releases, but hal/udev got along ok in the past

[Ole Juul]

Re: What's with HAL?

Thanks GG. I was just trying to figure out what is going on, hence the title. From what I hear people saying, HAL is a gonner. Looking, as you suggest, at the system monitor, suggests otherwise.

The "Upstart" addition is interesting. When trying to restart services I got several cryptic (to me) messages which suggested an upstart substitute. The suggestion seemed to work.

Since the script you are attempting to invoke has been converted to an
Upstart job, you may also use the restart (8 ) utility, e.g. restart autofs
autofs start/running, process 22406

GG: You haven't shown us the rules you are writing so it is hard to say what is "getting in their way".

I figured my personal computer problem would not be relevant in this thread. That was just what sparked an interest in what is going on with HAL. It looks like the documentation, in this case, has gotten ahead of the software. Anyway, from what I now understand, HAL is not quite gone yet and Upstart has been added to the mix.

@claydoh:
Yes, I am learning that hal and udev come along with the GUI. I wonder, is hal brought in with X11?

[claydoh]

Re: What's with HAL?

I don't know, but KDE itself still depends on hal (this is not distro-specific); whereas gnome does not. In Kubuntu/Ubuntu KDE packages would bring it in iirc

[GreyGeek]

Re: What's with HAL?

....
The "Upstart" addition is interesting. When trying to restart services I got several cryptic (to me) messages which suggested an upstart substitute. The suggestion seemed to work.

Since the script you are attempting to invoke has been converted to an
Upstart job, you may also use the restart (8 ) utility, e.g. restart autofs
autofs start/running, process 22406

.....

You may want to do a "man restart" and find out about initctl.

[Snowhog]

Re: What's with HAL?

There was discussion 'early on' in the development of hal of the amount of control it should have over the OS. The version numbering of hal didn't follow the 'standard model' as to all other components making up the system. The earliest version: hal 9.0.0-0ubuntu0 - although fully developed, was, during the final testing phase, found to have a few quirks that, under certain conditions, actually began to interfere with the safe operation of the OS, actually shutting down components critical to the user. It was discovered that shutting down hal was the only way that the user could regain control over the OS, even though it meant that those tasks that hal was designed to control would now have to be managed by the user. Those tasks were not trivial, and the development team ultimately considered that users would find managing those tasks manually just to much to ask of them.

Further development of the hal 9.0.0-0ubuntu0 series was therefore scrapped and rewritten from scratch.

[GreyGeek]

Re: What's with HAL?

Interesting info, Snowhog!

It just demonstrates that creating a "it just works", no (or little) config necessary, automatic desktop is NO trivial task.

EDIT: and still allow the user complete control. (Except, it seems, the ability to easily configure the xserver when HAL or Upstart fails to create a vaild configuration, as the recent Maverick upgrade login screen loop testifies.)