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Chapter 7. Technology Previews

This part provides a list of all Technology Previews available in Red Hat Enterprise Linux 8.10.

For information on Red Hat scope of support for Technology Preview features, see Technology Preview Features Support Scope.

7.1. Infrastructure services

Socket API for TuneD available as a Technology Preview

The socket API for controlling TuneD through a UNIX domain socket is now available as a Technology Preview. The socket API maps one-to-one with the D-Bus API and provides an alternative communication method for cases where D-Bus is not available. By using the socket API, you can control the TuneD daemon to optimize the performance, and change the values of various tuning parameters. The socket API is disabled by default, you can enable it in the tuned-main.conf file.

Bugzilla:2113900

7.2. Networking

AF_XDP available as a Technology Preview

Address Family eXpress Data Path (AF_XDP) socket is designed for high-performance packet processing. It accompanies XDP and grants efficient redirection of programmatically selected packets to user space applications for further processing.

Bugzilla:1633143[1]

XDP features that are available as Technology Preview

Red Hat provides the usage of the following eXpress Data Path (XDP) features as unsupported Technology Preview:

  • Loading XDP programs on architectures other than AMD and Intel 64-bit. Note that the libxdp library is not available for architectures other than AMD and Intel 64-bit.
  • The XDP hardware offloading.

Bugzilla:1889737

Multi-protocol Label Switching for TC available as a Technology Preview

The Multi-protocol Label Switching (MPLS) is an in-kernel data-forwarding mechanism to route traffic flow across enterprise networks. In an MPLS network, the router that receives packets decides the further route of the packets based on the labels attached to the packet. With the usage of labels, the MPLS network has the ability to handle packets with particular characteristics. For example, you can add tc filters for managing packets received from specific ports or carrying specific types of traffic, in a consistent way.

After packets enter the enterprise network, MPLS routers perform multiple operations on the packets, such as push to add a label, swap to update a label, and pop to remove a label. MPLS allows defining actions locally based on one or multiple labels in RHEL. You can configure routers and set traffic control (tc) filters to take appropriate actions on the packets based on the MPLS label stack entry (lse) elements, such as label, traffic class, bottom of stack, and time to live.

For example, the following command adds a filter to the enp0s1 network interface to match incoming packets having the first label 12323 and the second label 45832. On matching packets, the following actions are taken:

  • the first MPLS TTL is decremented (packet is dropped if TTL reaches 0)
  • the first MPLS label is changed to 549386

  • the resulting packet is transmitted over enp0s2, with destination MAC address 00:00:5E:00:53:01 and source MAC address 00:00:5E:00:53:02 

    # tc filter add dev enp0s1 ingress protocol mpls_uc flower mpls lse depth 1 label 12323 lse depth 2 label 45832 \
action mpls dec_ttl pipe \
action mpls modify label 549386 pipe \
action pedit ex munge eth dst set 00:00:5E:00:53:01 pipe \
action pedit ex munge eth src set 00:00:5E:00:53:02 pipe \
action mirred egress redirect dev enp0s2

Bugzilla:1814836[1], Bugzilla:1856415

act_mpls module available as a Technology Preview

The act_mpls module is now available in the kernel-modules-extra rpm as a Technology Preview. The module allows the application of Multiprotocol Label Switching (MPLS) actions with Traffic Control (TC) filters, for example, push and pop MPLS label stack entries with TC filters. The module also allows the Label, Traffic Class, Bottom of Stack, and Time to Live fields to be set independently.

Bugzilla:1839311[1]

The systemd-resolved service is now available as a Technology Preview

The systemd-resolved service provides name resolution to local applications. The service implements a caching and validating DNS stub resolver, a Link-Local Multicast Name Resolution (LLMNR), and Multicast DNS resolver and responder.

Note that, even if the systemd package provides systemd-resolved, this service is an unsupported Technology Preview.

Bugzilla:1906489

7.3. Kernel

Soft-RoCE available as a Technology Preview

Remote Direct Memory Access (RDMA) over Converged Ethernet (RoCE) is a network protocol that implements RDMA over Ethernet. Soft-RoCE is the software implementation of RoCE which maintains two protocol versions, RoCE v1 and RoCE v2. The Soft-RoCE driver, rdma_rxe, is available as an unsupported Technology Preview in RHEL 8.

Bugzilla:1605216[1]

eBPF available as a Technology Preview

Extended Berkeley Packet Filter (eBPF) is an in-kernel virtual machine that allows code execution in the kernel space, in the restricted sandbox environment with access to a limited set of functions.

The virtual machine includes a new system call bpf(), which enables creating various types of maps, and also allows to load programs in a special assembly-like code. The code is then loaded to the kernel and translated to the native machine code with just-in-time compilation. Note that the bpf() syscall can be successfully used only by a user with the CAP_SYS_ADMIN capability, such as the root user. See the bpf(2) manual page for more information.

The loaded programs can be attached onto a variety of points (sockets, tracepoints, packet reception) to receive and process data.

There are numerous components shipped by Red Hat that utilize the eBPF virtual machine. Each component is in a different development phase. All components are available as a Technology Preview, unless a specific component is indicated as supported.

The following notable eBPF components are currently available as a Technology Preview:

  • AF_XDP, a socket for connecting the eXpress Data Path (XDP) path to user space for applications that prioritize packet processing performance.

Bugzilla:1559616[1]

The kexec fast reboot feature is available as a Technology Preview

The kexec fast reboot feature continues to be available as a Technology Preview. The kexec fast reboot significantly speeds the boot process as you can boot directly into the second kernel without passing through the Basic Input/Output System (BIOS) or firmware first. To use this feature:

  1. Load the kexec kernel manually.
  2. Reboot for changes to take effect.

Note that the kexec fast reboot capability is available with a limited scope of support on RHEL 9 and later releases.

Bugzilla:1769727

The accel-config package available as a Technology Preview

The accel-config package is now available on Intel EM64T and AMD64 architectures as a Technology Preview. This package helps in controlling and configuring data-streaming accelerator (DSA) sub-system in the Linux Kernel. Also, it configures devices through sysfs (pseudo-filesystem), saves and loads the configuration in the json format.

Bugzilla:1843266[1]

7.4. File systems and storage

File system DAX is now available for ext4 and XFS as a Technology Preview

In Red Hat Enterprise Linux 8, the file system DAX is available as a Technology Preview. DAX provides a means for an application to directly map persistent memory into its address space. To use DAX, a system must have some form of persistent memory available, usually in the form of one or more Non-Volatile Dual In-line Memory Modules (NVDIMMs), and a file system that provides the capability of DAX must be created on the NVDIMM(s). Also, the file system must be mounted with the dax mount option. Then, a mmap of a file on the dax-mounted file system results in a direct mapping of storage into the application’s address space.

Bugzilla:1627455[1]

OverlayFS

OverlayFS is a type of union file system. It enables you to overlay one file system on top of another. Changes are recorded in the upper file system, while the lower file system remains unmodified. This allows multiple users to share a file-system image, such as a container or a DVD-ROM, where the base image is on read-only media.

OverlayFS remains a Technology Preview under most circumstances. As such, the kernel logs warnings when this technology is activated.

Full support is available for OverlayFS when used with supported container engines (podman, cri-o, or buildah) under the following restrictions:

  • OverlayFS is supported for use only as a container engine graph driver or other specialized use cases, such as squashed kdump initramfs. Its use is supported primarily for container COW content, not for persistent storage. You must place any persistent storage on non-OverlayFS volumes. You can use only the default container engine configuration: one level of overlay, one lowerdir, and both lower and upper levels are on the same file system.
  • Only XFS is currently supported for use as a lower layer file system.

Additionally, the following rules and limitations apply to using OverlayFS:

  • The OverlayFS kernel ABI and user-space behavior are not considered stable, and might change in future updates.

  • OverlayFS provides a restricted set of the POSIX standards. Test your application thoroughly before deploying it with OverlayFS. The following cases are not POSIX-compliant:

    • Lower files opened with O_RDONLY do not receive st_atime updates when the files are read.
    • Lower files opened with O_RDONLY, then mapped with MAP_SHARED are inconsistent with subsequent modification.

    • Fully compliant st_ino or d_ino values are not enabled by default on RHEL 8, but you can enable full POSIX compliance for them with a module option or mount option.

      To get consistent inode numbering, use the xino=on mount option.

      You can also use the redirect_dir=on and index=on options to improve POSIX compliance. These two options make the format of the upper layer incompatible with an overlay without these options. That is, you might get unexpected results or errors if you create an overlay with redirect_dir=on or index=on, unmount the overlay, then mount the overlay without these options.

  • To determine whether an existing XFS file system is eligible for use as an overlay, use the following command and see if the ftype=1 option is enabled: 

    # xfs_info /mount-point | grep ftype
  • SELinux security labels are enabled by default in all supported container engines with OverlayFS.
  • Several known issues are associated with OverlayFS in this release. For details, see Non-standard behavior in the Linux kernel documentation.

For more information about OverlayFS, see the Linux kernel documentation.

Bugzilla:1690207[1]

Stratis is now available as a Technology Preview

Stratis is a new local storage manager, which provides managed file systems on top of pools of storage with additional features. It is provided as a Technology Preview.

With Stratis, you can perform the following storage tasks:

  • Manage snapshots and thin provisioning
  • Automatically grow file system sizes as needed
  • Maintain file systems

To administer Stratis storage, use the stratis utility, which communicates with the stratisd background service. For more information, see the Setting up Stratis file systems documentation.

RHEL 8.5 updated Stratis to version 2.4.2. For more information, see the Stratis 2.4.2 Release Notes.

Jira:RHELPLAN-1212[1]

NVMe/TCP host is available as a Technology Preview

Accessing and sharing Nonvolatile Memory Express (NVMe) storage over TCP/IP networks (NVMe/TCP) and its corresponding nvme_tcp.ko kernel module has been added as a Technology Preview. The use of NVMe/TCP as a host is manageable with tools provided by the nvme-cli package. The NVMe/TCP host Technology Preview is included only for testing purposes and is not currently planned for full support.

Bugzilla:1696451[1]

Setting up a Samba server on an IdM domain member is provided as a Technology Preview

With this update, you can now set up a Samba server on an Identity Management (IdM) domain member. The new ipa-client-samba utility provided by the same-named package adds a Samba-specific Kerberos service principal to IdM and prepares the IdM client. For example, the utility creates the /etc/samba/smb.conf with the ID mapping configuration for the sss ID mapping back end. As a result, administrators can now set up Samba on an IdM domain member.

Due to IdM Trust Controllers not supporting the Global Catalog Service, AD-enrolled Windows hosts cannot find IdM users and groups in Windows. Additionally, IdM Trust Controllers do not support resolving IdM groups using the Distributed Computing Environment / Remote Procedure Calls (DCE/RPC) protocols. As a consequence, AD users can only access the Samba shares and printers from IdM clients.

For details, see Setting up Samba on an IdM domain member.

Jira:RHELPLAN-13195[1]

7.5. High availability and clusters

Pacemaker podman bundles available as a Technology Preview

Pacemaker container bundles now run on Podman, with the container bundle feature being available as a Technology Preview. There is one exception to this feature being Technology Preview: Red Hat fully supports the use of Pacemaker bundles for Red Hat OpenStack.

Bugzilla:1619620[1]

Heuristics in corosync-qdevice available as a Technology Preview

Heuristics are a set of commands executed locally on startup, cluster membership change, successful connect to corosync-qnetd, and, optionally, on a periodic basis. When all commands finish successfully on time (their return error code is zero), heuristics have passed; otherwise, they have failed. The heuristics result is sent to corosync-qnetd where it is used in calculations to determine which partition should be quorate.

Bugzilla:1784200

New fence-agents-heuristics-ping fence agent

As a Technology Preview, Pacemaker now provides the fence_heuristics_ping agent. This agent aims to open a class of experimental fence agents that do no actual fencing by themselves but instead exploit the behavior of fencing levels in a new way.

If the heuristics agent is configured on the same fencing level as the fence agent that does the actual fencing but is configured before that agent in sequence, fencing issues an off action on the heuristics agent before it attempts to do so on the agent that does the fencing. If the heuristics agent gives a negative result for the off action it is already clear that the fencing level is not going to succeed, causing Pacemaker fencing to skip the step of issuing the off action on the agent that does the fencing. A heuristics agent can exploit this behavior to prevent the agent that does the actual fencing from fencing a node under certain conditions.

A user might want to use this agent, especially in a two-node cluster, when it would not make sense for a node to fence the peer if it can know beforehand that it would not be able to take over the services properly. For example, it might not make sense for a node to take over services if it has problems reaching the networking uplink, making the services unreachable to clients, a situation which a ping to a router might detect in that case.

Bugzilla:1775847[1]

7.6. Identity Management

Identity Management JSON-RPC API available as Technology Preview

An API is available for Identity Management (IdM). To view the API, IdM also provides an API browser as a Technology Preview.

Previously, the IdM API was enhanced to enable multiple versions of API commands. These enhancements could change the behavior of a command in an incompatible way. Users are now able to continue using existing tools and scripts even if the IdM API changes. This enables:

  • Administrators to use previous or later versions of IdM on the server than on the managing client.
  • Developers can use a specific version of an IdM call, even if the IdM version changes on the server.

In all cases, the communication with the server is possible, regardless if one side uses, for example, a newer version that introduces new options for a feature.

For details on using the API, see Using the Identity Management API to Communicate with the IdM Server (TECHNOLOGY PREVIEW).

Bugzilla:1664719

DNSSEC available as Technology Preview in IdM

Identity Management (IdM) servers with integrated DNS now implement DNS Security Extensions (DNSSEC), a set of extensions to DNS that enhance security of the DNS protocol. DNS zones hosted on IdM servers can be automatically signed using DNSSEC. The cryptographic keys are automatically generated and rotated.

Users who decide to secure their DNS zones with DNSSEC are advised to read and follow these documents:

Note that IdM servers with integrated DNS use DNSSEC to validate DNS answers obtained from other DNS servers. This might affect the availability of DNS zones that are not configured in accordance with recommended naming practices.

Bugzilla:1664718

ACME available as a Technology Preview

The Automated Certificate Management Environment (ACME) service is now available in Identity Management (IdM) as a Technology Preview. ACME is a protocol for automated identifier validation and certificate issuance. Its goal is to improve security by reducing certificate lifetimes and avoiding manual processes from certificate lifecycle management.

In RHEL, the ACME service uses the Red Hat Certificate System (RHCS) PKI ACME responder. The RHCS ACME subsystem is automatically deployed on every certificate authority (CA) server in the IdM deployment, but it does not service requests until the administrator enables it. RHCS uses the acmeIPAServerCert profile when issuing ACME certificates. The validity period of issued certificates is 90 days. Enabling or disabling the ACME service affects the entire IdM deployment.

Important

It is recommended to enable ACME only in an IdM deployment where all servers are running RHEL 8.4 or later. Earlier RHEL versions do not include the ACME service, which can cause problems in mixed-version deployments. For example, a CA server without ACME can cause client connections to fail, because it uses a different DNS Subject Alternative Name (SAN).

Warning

Currently, RHCS does not remove expired certificates. Because ACME certificates expire after 90 days, the expired certificates can accumulate and this can affect performance.

  • To enable ACME across the whole IdM deployment, use the ipa-acme-manage enable command: 

    # ipa-acme-manage enable
The ipa-acme-manage command was successful

  • To disable ACME across the whole IdM deployment, use the ipa-acme-manage disable command: 

    # ipa-acme-manage disable
The ipa-acme-manage command was successful

  • To check whether the ACME service is installed and if it is enabled or disabled, use the ipa-acme-manage status command: 

    # ipa-acme-manage status
ACME is enabled
The ipa-acme-manage command was successful

Bugzilla:1628987[1]

sssd-idp sub-package available as a Technology Preview

The sssd-idp sub-package for SSSD contains the oidc_child and krb5 idp plugins, which are client-side components that perform OAuth2 authentication against Identity Management (IdM) servers. This feature is available only with IdM servers on RHEL 8.7 and later.

Bugzilla:2065692

SSSD internal krb5 idp plugin available as a Technology Preview

The SSSD krb5 idp plugin allows you to authenticate against an external identity provider (IdP) using the OAuth2 protocol. This feature is available only with IdM servers on RHEL 8.7 and later.

Bugzilla:2056483

7.7. Desktop

GNOME for the 64-bit ARM architecture available as a Technology Preview

The GNOME desktop environment is available for the 64-bit ARM architecture as a Technology Preview.

You can now connect to the desktop session on a 64-bit ARM server using VNC. As a result, you can manage the server using graphical applications.

A limited set of graphical applications is available on 64-bit ARM. For example:

  • The Firefox web browser
  • Red Hat Subscription Manager (subscription-manager-cockpit)
  • Firewall Configuration (firewall-config)
  • Disk Usage Analyzer (baobab)

Using Firefox, you can connect to the Cockpit service on the server.

Certain applications, such as LibreOffice, only provide a command-line interface, and their graphical interface is disabled.

Jira:RHELPLAN-27394[1], Bugzilla:1667516, Bugzilla:1724302, Bugzilla:1667225

GNOME for the IBM Z architecture available as a Technology Preview

The GNOME desktop environment is available for the IBM Z architecture as a Technology Preview.

You can now connect to the desktop session on an IBM Z server using VNC. As a result, you can manage the server using graphical applications.

A limited set of graphical applications is available on IBM Z. For example:

  • The Firefox web browser
  • Red Hat Subscription Manager (subscription-manager-cockpit)
  • Firewall Configuration (firewall-config)
  • Disk Usage Analyzer (baobab)

Using Firefox, you can connect to the Cockpit service on the server.

Certain applications, such as LibreOffice, only provide a command-line interface, and their graphical interface is disabled.

Jira:RHELPLAN-27737[1]

7.8. Graphics infrastructures

VNC remote console available as a Technology Preview for the 64-bit ARM architecture

On the 64-bit ARM architecture, the Virtual Network Computing (VNC) remote console is available as a Technology Preview. Note that the rest of the graphics stack is currently unverified for the 64-bit ARM architecture.

Bugzilla:1698565[1]

7.9. Virtualization

KVM virtualization is usable in RHEL 8 Hyper-V virtual machines

As a Technology Preview, nested KVM virtualization can now be used on the Microsoft Hyper-V hypervisor. As a result, you can create virtual machines on a RHEL 8 guest system running on a Hyper-V host.

Note that currently, this feature only works on Intel and AMD systems. In addition, nested virtualization is in some cases not enabled by default on Hyper-V. To enable it, see the following Microsoft documentation:

https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/user-guide/nested-virtualization

Bugzilla:1519039[1]

AMD SEV and SEV-ES for KVM virtual machines

As a Technology Preview, RHEL 8 provides the Secure Encrypted Virtualization (SEV) feature for AMD EPYC host machines that use the KVM hypervisor. If enabled on a virtual machine (VM), SEV encrypts the VM’s memory to protect the VM from access by the host. This increases the security of the VM.

In addition, the enhanced Encrypted State version of SEV (SEV-ES) is also provided as Technology Preview. SEV-ES encrypts all CPU register contents when a VM stops running. This prevents the host from modifying the VM’s CPU registers or reading any information from them.

Note that SEV and SEV-ES work only on the 2nd generation of AMD EPYC CPUs (codenamed Rome) or later. Also note that RHEL 8 includes SEV and SEV-ES encryption, but not the SEV and SEV-ES security attestation.

Bugzilla:1501618[1], Bugzilla:1501607, Jira:RHELPLAN-7677

Intel vGPU available as a Technology Preview

As a Technology Preview, it is possible to divide a physical Intel GPU device into multiple virtual devices referred to as mediated devices. These mediated devices can then be assigned to multiple virtual machines (VMs) as virtual GPUs. As a result, these VMs share the performance of a single physical Intel GPU.

Note that only selected Intel GPUs are compatible with the vGPU feature.

In addition, it is possible to enable a VNC console operated by Intel vGPU. By enabling it, users can connect to a VNC console of the VM and see the VM’s desktop hosted by Intel vGPU. However, this currently only works for RHEL guest operating systems.

Note that this feature is deprecated and will be removed entirely in a future RHEL major release.

Bugzilla:1528684[1]

Creating nested virtual machines

Nested KVM virtualization is provided as a Technology Preview for KVM virtual machines (VMs) running on Intel, AMD64, IBM POWER, and IBM Z systems hosts with RHEL 8. With this feature, a RHEL 7 or RHEL 8 VM that runs on a physical RHEL 8 host can act as a hypervisor, and host its own VMs.

Jira:RHELPLAN-14047[1], Jira:RHELPLAN-24437

Technology Preview: Select Intel network adapters now provide SR-IOV in RHEL guests on Hyper-V

As a Technology Preview, Red Hat Enterprise Linux guest operating systems running on a Hyper-V hypervisor can now use the single-root I/O virtualization (SR-IOV) feature for Intel network adapters that are supported by the ixgbevf and iavf drivers. This feature is enabled when the following conditions are met:

  • SR-IOV support is enabled for the network interface controller (NIC)
  • SR-IOV support is enabled for the virtual NIC
  • SR-IOV support is enabled for the virtual switch
  • The virtual function (VF) from the NIC is attached to the virtual machine

The feature is currently provided with Microsoft Windows Server 2016 and later.

Bugzilla:1348508[1]

Intel TDX in RHEL guests

As a Technology Preview, the Intel Trust Domain Extension (TDX) feature can now be used in RHEL 8.8 and later guest operating systems. If the host system supports TDX, you can deploy hardware-isolated RHEL 9 virtual machines (VMs), called trust domains (TDs). Note, however, that TDX currently does not work with kdump, and enabling TDX will cause kdump to fail on the VM.

Bugzilla:1836977[1]

Sharing files between hosts and VMs using virtiofs

As a Technology Preview, RHEL 8 now provides the virtio file system (virtiofs). Using virtiofs, you can efficiently share files between your host system and its virtual machines (VM).

Bugzilla:1741615[1]

7.10. RHEL in cloud environments

RHEL confidential VMs are now available on Azure as a Technology Preview

With the updated RHEL kernel, you can now create and run confidential virtual machines (VMs) on Microsoft Azure as a Technology Preview. However, it is not yet possible to encrypt RHEL confidential VM images during boot on Azure.

Jira:RHELPLAN-122316[1]

7.11. Containers

The podman-machine command is unsupported

The podman-machine command for managing virtual machines, is available only as a Technology Preview. Instead, run Podman directly from the command line.

Jira:RHELDOCS-16861[1]

Building multi-architecture images is available as a Technology Preview

The podman farm build command, which you can use to create multi-architecture container images, is available as a Technology Preview.

A farm is a group of machines that have a UNIX podman socket running in them. The nodes in the farm can have different machines of different architectures. The podman farm build command is faster than the podman build --arch --platform command.

You can use podman farm build to perform the following actions:

  • Build an image on all nodes in a farm.
  • Bundle nodes up into a manifest list.
  • Execute the podman build command on all the farm nodes.
  • Push the images to the registry specified by using the --tag option.
  • Locally create a manifest list.

  • Push the manifest list to the registry.

    The manifest list contains one image per native architecture type that is present in the farm.

Jira:RHELPLAN-154435[1]

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