Chapter 37. Parameters and configuration files on 64-bit IBM Z

This section contains information about the parameters and configuration files on 64-bit IBM Z.

37.1. Required configuration file parameters on 64-bit IBM Z

Several parameters are required and must be included in the parameter file. These parameters are also provided in the file generic.prm in directory images/ of the installation DVD.

  • ro

    Mounts the root file system, which is a RAM disk, read-only.

  • ramdisk_size=size

    Modifies the memory size reserved for the RAM disk to ensure that the Red Hat Enterprise Linux installation program fits within it. For example: ramdisk_size=40000.

The generic.prm file also contains the additional parameter cio_ignore=all,!condev. This setting speeds up boot and device detection on systems with many devices. The installation program transparently handles the activation of ignored devices.

37.2. 64-bit IBM Z/VM configuration file

Under z/VM, you can use a configuration file on a CMS-formatted disk. The purpose of the CMS configuration file is to save space in the parameter file by moving the parameters that configure the initial network setup, the DASD, and the FCP specification out of the parameter file.

Each line of the CMS configuration file contains a single variable and its associated value, in the following shell-style syntax: variable=value.

You must also add the CMSDASD and CMSCONFFILE parameters to the parameter file. These parameters point the installation program to the configuration file:


Where cmsdasd_address is the device number of a CMS-formatted disk that contains the configuration file. This is usually the CMS user’s A disk.

For example: CMSDASD=191


Where configuration_file is the name of the configuration file. This value must be specified in lower case. It is specified in a Linux file name format: CMS_file_name.CMS_file_type.

The CMS file REDHAT CONF is specified as redhat.conf. The CMS file name and the file type can each be from one to eight characters that follow the CMS conventions.

For example: CMSCONFFILE=redhat.conf

37.3. Installation network, DASD and FCP parameters on 64-bit IBM Z

These parameters can be used to automatically set up the preliminary network, and can be defined in the CMS configuration file. These parameters are the only parameters that can also be used in a CMS configuration file. All other parameters in other sections must be specified in the parameter file.


Where type must be one of the following: qeth, lcs, or ctc. The default is qeth.

Choose lcs for:

  • OSA-Express features

Choose qeth for:

  • OSA-Express features
  • HiperSockets
  • Virtual connections on z/VM, including VSWTICH and Guest LAN

Where device_bus_IDs is a comma-separated list of two or three device bus IDs. The IDs must be specified in lowercase.

Provides required device bus IDs for the various network interfaces:

qeth: SUBCHANNELS="read_device_bus_id,write_device_bus_id,data_device_bus_id"
lcs or ctc: SUBCHANNELS="read_device_bus_id,write_device_bus_id"

For example (a sample qeth SUBCHANNEL statement):

PORTNAME="osa_portname" PORTNAME="lcs_portnumber"

This variable supports OSA devices operating in qdio mode or in non-qdio mode.

When using qdio mode (NETTYPE="qeth"), osa_portname is the portname specified on the OSA device when operating in qeth mode.

When using non-qdio mode (NETTYPE="lcs"), lcs_portnumber is used to pass the relative port number as a decimal integer in the range of 0 through 15.

You can add either PORTNO="0" (to use port 0) or PORTNO="1" (to use port 1 of OSA features with two ports per CHPID) to the CMS configuration file to avoid being prompted for the mode.

Where value can be 0 or 1.

Use LAYER2="0" to operate an OSA or HiperSockets device in layer 3 mode (NETTYPE="qeth"). Use LAYER2="1" for layer 2 mode. For virtual network devices under z/VM this setting must match the definition of the GuestLAN or VSWITCH to which the device is coupled.

To use network services that operate on layer 2 (the Data Link Layer or its MAC sublayer) such as DHCP, layer 2 mode is a good choice.

The qeth device driver default for OSA devices is now layer 2 mode. To continue using the previous default of layer 3 mode, set LAYER2="0" explicitly.


Where value can be 0 or 1.

Specify VSWITCH="1" when connecting to a z/VM VSWITCH or GuestLAN, or VSWITCH="0" (or nothing at all) when using directly attached real OSA or directly attached real HiperSockets.


If you specify LAYER2="1" and VSWITCH="0", you can optionally use this parameter to specify a MAC address. Linux requires six colon-separated octets as pairs lower case hex digits - for example, MACADDR=62:a3:18:e7:bc:5f. Note that this is different from the notation used by z/VM.

If you specify LAYER2="1" and VSWITCH="1", you must not specify the MACADDR, because z/VM assigns a unique MAC address to virtual network devices in layer 2 mode.


Where value can be 0, 1, or 3.

Specifies the CTC protocol for NETTYPE="ctc". The default is 0.

Where string is the host name of the newly-installed Linux instance.
Where IP is the IP address of the new Linux instance.

Where netmask is the netmask.

The netmask supports the syntax of a prefix integer (from 1 to 32) as specified in IPv4 classless interdomain routing (CIDR). For example, you can specify 24 instead of, or 20 instead of

Where gw is the gateway IP address for this network device.
Where mtu is the Maximum Transmission Unit (MTU) for this network device.

Where "server1:server2:additional_server_terms:serverN" is a list of DNS servers, separated by colons. For example:


Where "domain1:domain2:additional_dns_terms:domainN" is a list of the search domains, separated by colons. For example:


You only need to specify SEARCHDNS= if you specify the DNS= parameter.


Defines the DASD or range of DASDs to configure for the installation.

The installation program supports a comma-separated list of device bus IDs, or ranges of device bus IDs with the optional attributes ro, diag, erplog, and failfast. Optionally, you can abbreviate device bus IDs to device numbers with leading zeros stripped. Any optional attributes should be separated by colons and enclosed in parentheses. Optional attributes follow a device bus ID or a range of device bus IDs.

The only supported global option is autodetect. This does not support the specification of non-existent DASDs to reserve kernel device names for later addition of DASDs. Use persistent DASD device names such as /dev/disk/by-path/name to enable transparent addition of disks later. Other global options such as probeonly, nopav, or nofcx are not supported by the installation program.

Only specify those DASDs that need to be installed on your system. All unformatted DASDs specified here must be formatted after a confirmation later on in the installation program.

Add any data DASDs that are not needed for the root file system or the /boot partition after installation.

For example:

FCP_n="device_bus_ID [WWPN FCP_LUN]"

For FCP-only environments, remove the DASD= option from the CMS configuration file to indicate no DASD is present.

FCP_n="device_bus_ID [WWPN FCP_LUN]"


  • n is typically an integer value (for example FCP_1 or FCP_2) but could be any string with alphabetic or numeric characters or underscores.
  • device_bus_ID specifies the device bus ID of the FCP device representing the host bus adapter (HBA) (for example 0.0.fc00 for device fc00).
  • WWPN is the world wide port name used for routing (often in conjunction with multipathing) and is as a 16-digit hex value (for example 0x50050763050b073d).
  • FCP_LUN refers to the storage logical unit identifier and is specified as a 16-digit hexadecimal value padded with zeroes to the right (for example 0x4020400100000000).

A target world wide port name (WWPN) and an FCP_LUN have to be provided if the zFCP device is not configured in NPIV mode, when auto LUN scanning is disabled by the zfcp.allow_lun_scan=0 kernel module parameter or when installing RHEL-8.6 or older releases. Otherwise only the device_bus_ID value is mandatory.

  • These variables can be used on systems with FCP devices to activate FCP LUNs such as SCSI disks. Additional FCP LUNs can be activated during the installation interactively or by means of a Kickstart file. An example value looks similar to the following:

    FCP_1="0.0.fc00 0x50050763050b073d 0x4020400100000000"

    Each of the values used in the FCP parameters (for example FCP_1 or FCP_2) are site-specific and are normally supplied by the FCP storage administrator.

37.4. Parameters for kickstart installations on 64-bit IBM Z

The following parameters can be defined in a parameter file but do not work in a CMS configuration file.

References a Kickstart file, which usually resides on the network for Linux installations on 64-bit IBM Z. Replace URL with the full path including the file name of the Kickstart file. This parameter activates automatic installation with Kickstart.
This requires installation with a Kickstart file that answers all questions, because the installation program does not support interactive user input in cmdline mode. Ensure that your Kickstart file contains all required parameters before you use the inst.cmdline option. If a required command is missing, the installation will fail.

37.5. Miscellaneous parameters on 64-bit IBM Z

The following parameters can be defined in a parameter file but do not work in a CMS configuration file.
Turns on testing of an ISO-based installation source; for example, when using inst.repo= with an ISO on local hard disk or mounted with NFS.
Disables support for multipath devices.
Specify a proxy to use with installation over HTTP, HTTPS or FTP.
Boot into a rescue system running from a RAM disk that can be used to fix and restore an installed system.

Specifies a path to a tree containing install.img, not to the install.img directly. Otherwise, follows the same syntax as inst.repo=. If inst.stage2 is specified, it typically takes precedence over other methods of finding install.img. However, if Anaconda finds install.img on local media, the inst.stage2 URL will be ignored.

If inst.stage2 is not specified and install.img cannot be found locally, Anaconda looks to the location given by inst.repo= or method=.

If only inst.stage2= is given without inst.repo= or method=, Anaconda uses whatever repos the installed system would have enabled by default for installation.

Use the option multiple times to specify multiple HTTP, HTTPS or FTP sources. The HTTP, HTTPS or FTP paths are then tried sequentially until one succeeds:

Sends log messages to a remote syslog server.

The boot parameters described here are the most useful for installations and trouble shooting on 64-bit IBM Z, but only a subset of those that influence the installation program.

37.6. Sample parameter file and CMS configuration file on 64-bit IBM Z

To change the parameter file, begin by extending the shipped generic.prm file.

Example of generic.prm file:

ro ramdisk_size=40000 cio_ignore=all,!condev
CMSDASD="191" CMSCONFFILE="redhat.conf"

Example of redhat.conf file configuring a QETH network device (pointed to by CMSCONFFILE in generic.prm):


Additional resources