Managing Network Device Discovery Services (Task Map)

How Auto-Discovery of Devices Works

Discovery of devices, including printers, is accomplished through the Hardware Abstraction Layer (HAL) device registry (database) component. HAL uses D-BUS messaging to notify interested applications about changes to its registry. D-BUS is a messaging bus that passes messages between applications and broadcasts signals that interested applications are able to detect. This messaging service is used by HAL and a number of other applications. HAL provides the framework for device discovery and notification of device configuration changes on a system. In the Oracle Solaris release, this support has been extended to detecting printers that are added or removed from a local system.

The HAL daemon, hald, provides a view of devices that are attached to a local system. This view is updated automatically, as a system's hardware configuration changes, by hotplugging or by other methods. HAL's internal database, also called the HAL device tree, is where device information is stored and maintained. HAL devices are uniquely identified in the HAL database through a Universal Device Identifier (UDI). This database is populated with properties of each device in the HAL database.

The automatic printing configuration feature works with the HAL daemon by listening for sysevents. When a hotplug-capable printer is added to a system, HAL creates a new node in the HAL device tree, as shown in the following example:

/org/freedesktop/Hal/devices/pci_0_0/pci1022_74606/pci108e_534d_3_1/printer_2_0_if0/print

When the device node has been successfully registered in the HAL database, HAL signals interested applications that the device is available. Device removal works similarly.

The network device discovery components are standard service interfaces that are offered by classes of network-attached devices. This module is capable of actively scanning a network for new devices. The service is directly controlled through the svcadm interface. For more information, see the svcadm(1M) man page. svcadm(1M). To determine the device type, an active scan is performed through a Simple Network Management Protocol version 1 (SNMPv1) broadcast. By default, the SNMP based network-attached printer discovery service probes the network for printers every 60 seconds. This property is configurable. See Configuring Auto-Discovery Settings for Network-Attached Printers. During this active scan, SNMP determines the device type by attempting to connect to the device.

Issues With the Network-Attached Printer Discovery Service Under LP

In the Oracle Solaris 11 Express release, the network-attached printer discovery service that is used by the LP print service and its management tools does not work as expected. Any attempts to manually enable the device-discovery/printers:snmp service fails, causing the service to revert to a maintenance state.

Note that if CUPS, the default print service in this Oracle Solaris release is used, the device-discovery/printers:snmp service is not needed. However, if you need to switch to the LP service and network-attached printer discovery is required, this service must be enabled. Prior to enabling the device-discovery/printers:snmp service, complete these steps:

1. Become superuser.

2. Install the SUNWnet-snmp-core software package on your system.

   # pkg install SUNWnet-snmp-core

   Alternatively, you can use the Package Manager GUI to add the software package to your system.

3. Update the /etc/dbus-1/system.d/hal.conf file, as follows:

   # patch -b /etc/dbus-1/system.d/hal.conf <<EOF>
   +++ hal.conf    Sun Sep  6 00:49:33 2009
        @@ -32,6 +32,8 @@
                    send_destination="org.freedesktop.Hal"/>
                   <allow send_interface="org.freedesktop.Hal.Device.CPUFreq"
                    send_destination="org.freedesktop.Hal"/>
   +                <allow send_interface="org.freedesktop.Hal.Device.NetworkDiscovery"
   +           send_destination="org.freedesktop.Hal"/>
           </policy>
                   <!-- Default policy for the exported interfaces -->
   EOF

4. Restart the HAL service.

   # svcadm restart hal

5. Start the device-discovery/printers:snmp service.

   # svcadm enable printers:snmp

How to Enable the Network Device Discovery Service From the Desktop

By default, USB printers that are physically connected to your system are automatically detected and partially configured. Print Manager for LP also has the ability to discover and configure printers that are on a network if the network device discovery service has been enabled.

Before You Begin

The network device discovery service cannot be enabled from the desktop until you install the SUNWnet-snmp-core software package. If you attempt to enable the service before installing this package, the system reverts to maintenance state. Before you enable the network device discovery service, perform the workaround that is described in Issues With the Network-Attached Printer Discovery Service Under LP.

1. From the Main Menubar of the GNOME Desktop, choose:

   System-> Administration-> Services

   The Services settings window is displayed.

2. To initiate the device discovery add-on module, select the Hardware Abstraction Layer network-attached printer discovery (network/device-discovery/printers:snmp) option.
3. Save your changes.

   To disable auto-discovery of devices, deselect this option.

How to Enable Network Device Discovery Services by Using SMF

This procedure describes how to enable and disable the network device-discovery/printers service (the HAL add-on module) by using the SMF.

1. Become superuser .
2. Determine whether the SMF device-discovery/printers service is online.

   # svcs device-discovery/printers

   If the service is online, the following output is displayed:

   STATE          STIME    FMRI
   online         13:30:22 svc:/network/device-discovery/printers:snmp

   If the service is offline, the following output is displayed:

   STATE          STIME    FMRI
   disabled       Dec_12   svc:/network/device-discovery/printers:snmp

3. To enable or disable the service instance, use the appropriate command.
   • To enable the service, type:

     # svcadm enable printers:snmp

   • To disable the service, type:

     # svcadm disable printers:snmp

4. Verify that the HAL add-on module has been enabled or disabled.

   If the module has been successfully enabled, the output is as follows:

   # svcs device-discovery/printers
   STATE          STIME    FMRI
   online         13:30:22 svc:/network/device-discovery/printers:snmp 

   If the module has been successfully disabled, the output is as follows:

   # svcs device-discovery/printers
   STATE          STIME    FMRI
   disabled       Dec_12   svc:/network/device-discovery/printers:snmp

How to Determine Which Printers Are Known to the System

• On the system that you want to get information about discovered printers, type:

  $ for udi in `hal-find-by-capability --capability printer` ; do ; lshal --show $udi --long ; done

Example 4-1 Determining Which Printers Are Known to the System

This example shows all of the devices discovered by the system snoopy.

mymachine% PS1="$ " /bin/sh
$ for udi in `hal-find-by-capability --capability printer` ; do
> lshal --show $udi --long ; done
udi = '/org/freedesktop/Hal/devices/network_attached/LLADDR_000E7FD91F07'
      printer.commandset = {'PJL', 'MLC', 'BIDI-ECP', 'PCLXL', 'PCL', 'PDF', \
'PJL', 'MIME', 'POSTSCRIPT'} (string list)
      info.product = 'hp color LaserJet 4650'  (string)
      org.freedesktop.Hal.Device.Printer.method_argnames = {'make model'} (string list)
      org.freedesktop.Hal.Device.Printer.method_execpaths = {'hal_lpadmin --configure'} (string list)
      org.freedesktop.Hal.Device.Printer.method_signatures = {'ss'} (string list)
.
.
.
    
    $