What are rc.messagebus and rc.hald for?

FreeTinker · 03-07-2008, 10:15 PM

During Slackware 12 installation there is the question asking whether to install rc.messagebus and rc.hald. What are these two for? Can I not install them?

weibullguy · 03-07-2008, 11:09 PM

messagebus is the D-Bus daemon and hald is the HAL daemon. Neither is strictly required, but you'll find many packages use them to point that they're essentially required for a modern Linux desktop.

willysr · 03-08-2008, 12:44 AM

yes, you can choose not to install the packages (it's your system anyways), but i guess you will lose lots of functionality or it may not work

H_TeXMeX_H · 03-08-2008, 03:16 AM

Of course it will work without these packages, but you will indeed not really lose functionality, but rather not gain it

JMJ_coder · 03-08-2008, 08:40 PM

Hello,

What does the HAL Daemon do? And what does the D-Bus daemon do?

What wouldn't you be able to do if you didn't have them installed in running on your system that you could if you did?

willysr · 03-09-2008, 12:15 AM

taken from the slack-desc

Quote:

hal: hal (The HAL Hardware Abstraction Layer)
hal:
hal: HAL is a piece of software that provides a view of the various
hal: hardware attached to a system. HAL keeps detailed metadata for each
hal: piece of hardware and provides hooks so that system and desktop
hal: software can react to changes in the hardware configuration (such as
hal: the insertion of a DVD, or a USB flash memory stick). Users in the
hal: "plugdev" or "cdrom" group will be able to use such devices on the
hal: desktop without the need to mount/umount them manually.

Quote:

dbus: dbus (D-Bus message bus system)
dbus:
dbus: D-Bus supplies both a system daemon (for events such as "new hardware
dbus: device added" or "printer queue changed") and a per user login
dbus: session daemon (for general IPC needs among user applications).
dbus: Also, the message bus is built on top of a general one-to-one message
dbus: passing framework, which can be used by any two apps to communicate
dbus: directly (without going through the message bus daemon).

2.718281828 · 03-09-2008, 12:47 AM

Personally, I'd much rather mount my removable devices manually, so I wouldn't touch HAL with a ten foot pole. As far as D-Bus goes, I've never heard of it until just now and I'm still not sure what it does from that package description. I don't use either of them on my computer so maybe my computer doesn't count as a "modern" Linux system...

willysr · 03-09-2008, 04:44 AM

i also use manual mounting, since i can set it up to use one single moint point

JMJ_coder · 03-10-2008, 02:33 PM

Hello,

So if I got rid of HAL, exactly what functionality would cease? Auto-mounting? I mount via terminal (mount/umount command). I don't think that my printers being turned on and off count as auto-mounting either.

So if you aren't running say, Fedora, that is set up to automatically mount (and even execute a program) upon inserting a disc or plugging in a device, what is the point of having it?

I still don't know what D-Bus does? That package description isn't overtly descriptive for someone who doesn't already know what D-Bus does.

weibullguy · 03-10-2008, 03:53 PM

D-BUS is an inter-process communication (IPC) system. D-BUS allows programs to register, offering services to other programs. Client programs are provided the opportunity to "look up" which services are available.

Users can run several channels of D-BUS since D-BUS is implemented as a daemon. Usually there is a system channel and a private channel for each logged user. The primary mission of the system channel is to deliver signals from the HAL daemon to the processes interested in them. The mission of the private channels is to provide communication among the user's applications.

There are Glib, Qt, Python, and Java bindings for D-Bus. Lot's of applications use D-Bus like Xchat, Pidgin, libnotify, Avahi, Totem, Rhythmbox, Evince, Xorg server and others. IIRC, GNOME, KDE, and XFCE all have at least one module that require D-Bus.

I think KDE4 requires HAL, but I could be wrong. I know GNOME Volume Manager requires HAL, but most applications only have it as an optional dependency.