Changing device or device driver settings

6.10 LPAR mode z/VM guest KVM guest

Use the chzdev command to change both device and device driver settings.

About this task

Some devices provide named attributes. You can change the value of the attributes by using the chzdev command with a <attribute=value> assignment.

You can also use the chzdev command to modify device driver attributes, for example module parameters such as the DASD module parameter eer_pages. You select a device driver, rather than a device, by specifying 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.

where:

<attribute=value>

specifies a device attribute and its value. To specify multiple attributes, separate attribute-value pairs with a blank.

You can use the --list-attributes option to display a list of available attributes and the --help-attribute to get more detailed information about a specific attribute.

Tip: To specify an attribute that is not known to chzdev, use the --force option.

-r or --remove <attrib>

removes the setting for attribute <attrib>.

Active configuration: For attributes that maintain a list of values, clears all values for that list.
Persistent configuration: Removes any setting for the specified attribute. When the device or device driver is configured again, the attribute is set to its default value.
You can limit this persistent change to a particular site.

Some attributes cannot be removed.

-R or --remove-all

removes the settings for all attributes of the selected device or device driver.

Active configuration: For attributes that maintain a list of values, clears all values for that list.
Persistent configuration: Removes all attribute settings that can be removed. When the device or device driver is configured again, the attribute is set to its default value.
You can limit this persistent change to a particular site.

Some attributes cannot be removed.

-f or --force

overrides safety checks and confirmation questions, including:

More than 256 devices selected
Configuring unknown attributes
Combining apparently inconsistent settings

Examples for changing device settings

To set the use_diag attribute for device 0.0.8000, issue:

# chzdev dasd-fba 0.0.8000 use_diag=1 --persistent --verbose
Configuring devices in the persistent configuration only
FBA DASD 0.0.8000 configured
    Changes: use_diag=1
    Block devices: /dev/dasda /dev/dasda1

To set the use_diag attribute for device 0.0.f001 in the site-specific configuration for site 0, issue:

# chzdev f001 --site 0 use_diag=1
Configuring devices in the site 0 configuration only
ECKD DASD 0.0.f001 configured

To list available attributes, specify the device type together with the --list-attributes option:

# chzdev dasd-fba --list-attributes
NAME                        DESCRIPTION
online                       Activate a device
cmb_enable                   Enable the Channel measurement facility
failfast                     Modify error recovery in no-path scenario
readonly                     Inhibit write access to DASD
erplog                       Enable logging of Error Recovery Processing
use_diag                     Activate z/VM hypervisor assisted I/O processing
eer_enabled                  Enable Extended Error Reporting
expires                      Modify I/O operation timeout
retries                      Modify I/O operation retry counter
timeout                      Modify I/O request timeout
reservation_policy           Modify lost device reservation behavior
last_known_reservation_state Display and reset driver device reservation view
safe_offline                 Deactivate DASD after processing outstanding I/Os

To display more details about an attribute, use the --help-attribute option:

# chzdev dasd-fba --help-attribute use_diag
ATTRIBUTE use_diag

  DESCRIPTION
    Control I/O access mode for a DASD:
      0: I/O is performed using standard channel programs
      1: I/O is performed using the z/VM DIAGNOSE X’250’ interface

Note that the DIAGNOSE X’250’ access mode only works when running
Linux as z/VM guest, and only for devices formatted with consistent
block sizes such as ECKD DASDs with LDL or CMS format, or FBA
devices.

DEFAULT VALUE
  The default value is ’0’.
ACCEPTED VALUES
  - Numbers 0 to 1 in decimal notation

To remove a setting from a persistent configuration, use the --remove and --persistent options:

# chzdev dasd 8000 --persistent --remove use_diag --verbose
Configuring devices in the persistent configuration only
FBA DASD 0.0.8000 configured
    Changes: -use_diag
    Block devices: /dev/dasda /dev/dasda1

Example for changing device driver settings

To change device driver settings, use a <attribute=value> assignment together with the device type:

# chzdev dasd --type nopav=1
dasd device type configured