Persistent device configuration
Use the chzdev command to persistently configure your devices and device drivers and the lszdev command to view your configuration.
You can manage the device configuration with lszdev and chzdev within all hypervisor environments, LPAR, z/VM®, and KVM. For KVM guests, this applies mainly to passthrough devices. For virtio devices, the virtual server definition on the KVM host and the KVM virtualization limit the scope for configuration on the KVM guest.
Mainframe-specific devices, such as DASDs, FCP devices, and network devices require special configuration steps before they can be used. Tools are available that configure devices, for example chccwdev and znetconf, but this type of configuration is not preserved across reboots.
The chzdev command facilitates persistent configuration. The command performs all configuration steps that are required to make devices operational, for example, as a block device, a character device, or a network interface.
- FICON-attached direct access storage devices (DASDs)
- SCSI-over-Fibre Channel (FCP) devices and SCSI devices
- OSA-Express and HiperSockets network devices
- Channel-to-channel (CTC) and CTC-MPC network devices
- LAN-Channel-Station (LCS) network devices
- Channel command word (CCW) devices that are not covered by any other device type, for example the 3215 console, 3270 terminal devices, z/VM reader and puncher devices, and CCW tape devices.
The lszdev command displays configuration information about devices and device drivers. For details, see lszdev - Display IBM Z device configurations.
For details about the chzdev command, see chzdev - Configure IBM Z devices.
Configuration scope
- Active configuration
- The active configuration is the configuration that is used by the running Linux® instance.
- Persistent configuration
- The persistent configuration is the configuration as represented in configuration
files such as udev rules.
A special type of persistent configuration is a site-specific configuration, which applies to a particular site only, see Site-specific Linux instantiation. This configuration scope is available only for DASD.
Use the --site option of the chzdev command to configure DASDs for the scope of a particular site. Use the --site option of the lszdev command to display device information as applicable to a particular site.
Device ID
The chzdev and lszdev commands use device IDs to identify devices. For CCW devices and CCW group devices, this device ID is the device bus-ID.
The device bus-ID is of the format 0.<subchannel_set_ID>.<devno>, for example, 0.0.8000.
Configuring device drivers
You can use the chzdev command to modify device driver attributes, for example
module parameters such as DASD's eer_pages. You select a device driver, rather than
a device, by using the --type option. Device drivers can be selected by type or
sub-type, for example DASDs are of type dasd, but have the sub-types dasd-fba and dasd-eckd.
chzdev syntax overview
Where the different command sections have these meanings:
- Device or device type selection
- Select devices by device ID, device state, or function. Select device types by specifying a device type and the --type option. For details about selecting devices or device types, see Selecting devices and device drivers.
- Actions
- Perform an action against the selected devices. For details about these actions, see:
- Options
- Choose how to apply the command, for example as a test run, as applying to the persistent configuration only, or as running in quiet mode. Options include --dry-run, --verbose, --quiet, and --yes. For the complete list of options, see chzdev - Configure IBM Z devices
lszdev syntax overview
Where the different command sections have these meanings:
- Device or device type selection
- Select devices to display by device ID, device state, or function. For details about selecting devices, see Selecting devices and device drivers. If no selection is made, all existing and configured devices are displayed.
- Options
- Choose the configuration information, and how to display it.
- To display a list with information about all devices, specify only lszdev without options. You can restrict output to a single device, a device type, or a range of devices. You can control what information is included by specifying output columns.
- To display details about a single device, specify the device and the --info option.