Virtual I/O Server release notes

The release notes for Virtual I/O Server (VIOS) Version are available.

VIOS best practice recommendations

To ensure the reliability, availability, and serviceability of a computing environment by using the Virtual I/O Server (VIOS), update the VIOS software to the most recent fix level for that particular release. The most recent level contains the latest fixes for the specified VIOS release. You can download the most recent updates for VIOS from the IBM® Fix Central website (

VIOS package terminology

To view the most current version of the VIOS package terminology and maintenance strategy, see the VIOS Maintenance Strategy website (

Read this information before installing VIOS

To stay up to date on VIOS news and critical product updates, subscribe to the VIOS notification service.

To subscribe to the VIOS notification service, go to My notifications on the IBM Support Portal website ( and sign in by using your IBM ID. Enter PowerVM® Virtual I/O Server into Product lookup, and click Subscribe.

To manage your IBM customer numbers and your company's user access to IBM server, see IBM Support and select IBM Entitled Software Support. Sign in by using your IBM ID.

VIOS version installation

The VIOS software is distributed in a single DVD.

You can also install VIOS by using a USB flash drive.

Memory requirements

The minimum memory requirement for the VIOS Version varies based on the configuration.

The minimum memory requirement for the VIOS Version is 4 GB. A minimum current memory requirement might support a configuration with a minimum number of devices or a small maximum memory configuration. However, to support shared storage pools, the minimum memory requirement is 4 GB.

The VIOS Version requires the minimum current memory requirement to increase when either the maximum memory configuration or the number of devices increases, or when they both increase. Larger maximum memory configurations or more devices increase the minimum current memory requirement. If the minimum memory requirements do not increase along with the maximum memory configuration, the partition stops during the initial program load (IPL).

ROOTVG requirements

The VIOS Version requires a minimum of 30 GB of disk space for installation. Ensure that the disk that is allocated for the VIOS installation contains at least 30 GB of available space before you attempt to install VIOS.

VIOS Version enhancements

This release of VIOS contains several enhancements in PowerVM virtualization area.

Security enhancements

The security enhancements for this release are as follows:

  • Trusted Execution, Trusted Update, and Secure Boot features are supported.
  • Strong default passwords like SSHA-256 and long passwords with 255 character limit are supported.
  • Data protection with Logical Volume Manager (LVM) encryption for the rootvg and dump devices is available.
  • The rexec and rsh services that are nonsecure are removed.
  • The Telnet and ftp services that are nonsecure are disabled. However, you can enable the Telnet and ftp services, if required.
  • The ksh93 command is used as default in VIOS commands and scripts. The users of the ksh shell must consider using the ksh93 shell.

VIOS upgrade enhancements

For this release, the following major enhancements are made in the viosupgrade command:
  • The -F devname flag is added to preserve the device names for:
    1. vfchost adapter device
    2. fcnvme device
    3. nvme device
    4. fcsci device
    5. iSCSI device
    6. Network adapter device
  • The -k and -o rerun flags are added, which are specific to pre-restore script execution.
    • The existing VIOS systems can be upgraded to VIOS version
    • The upgrade operation is supported for VIOS version, or later.
    • The upgrade operation might give unexpected results if you are upgrading from a version earlier than VIOS version, or later.

Other VIOS command enhancements

For this release, the following enhancements are made to other VIOS commands:
  • The alt_root_vg command is enhanced to run in phases. This enhancement allows the alt_root_vg command to separate the cloning phase from the update phase.
  • The snap command is enhanced with the -gzip option to use the on-chip NX GZIP accelerator for faster compression.
  • The viosbr command restores all physical volume (PV)-backed Virtual Target Devices (VTD) if the same PV is mapped to multiple Virtual SCSI server adapters (vHosts).

Software Updates in VIOS version

  • Python 3 is added.
  • PostgreSQL 15.3 is added. PostgreSQL 13 is updated to PostgreSQL 13.11.

Features removed in VIOS version

The following features were removed from this release:
  1. ITM Software: ITM (IBM Tivoli Monitoring) filesets are not part of VIOS version, or later. You must download and install the ITM filesets from an external location. You can download and install the agents separately as a part of the updated IBM Tivoli Monitoring System P bundle. To know more, see IBM Tivoli Monitoring: System P Agents 6.2.2 Fix Pack 4 readme file.
  2. AMS: Active Memory Sharing (AMS) feature is removed.

Handling existing NFSv4 mounts on VIOS

The ioscli mount command which previously, by default, only supported the NFSv3 mount of the AIX® operating system is updated to support NFSv4 mounting. This update allows VIOS to invoke commands for the following actions:

  • Setting NFS domain by using the chnfsdom command

    You can set the NFS domain by adding a Role-based access control (RBAC) support for the chnfsdom command.

  • Invoking the NFSv4 mounting
    The ioscli mount command is updated to support invoking the NFSv4 mounting. The current ioscli mount command defaults to NFSv3. You can invoke the “o vers=4” option with the new “-nfsvers <version> <Node: > <Directory> < Directory>” option that is added to the ioscli mount command. The values that are supported for the version are 3 and 4.
    Note: The ioscli mount command supports NFS versions that are supported by the AIX mount command.
  • Starting the nfsrgyd daemon

    For version 4, if the mount is successful, a check is done to see whether the nfsrgyd daemon is already started, and if it is not yet started, the nfsrgyd daemon is started.