NCN Kernel

This page provides information on the Linux kernel in the non-compute nodes (NCNs).

Locks

The Kernel version is controlled by the kernel-default package, and this package is locked. Locking this package prevents accidental updates.

To view the locks, run zypper locks.

To remove the lock, run zypper removelock kernel-default.

To add set the lock, run zypper addlock kernel-default.

Module blacklisting

The following kernel modules are blacklisted from loading on the NCNs:

  • rpcrdma due to conflicts with slingshot.

Parameters

Below are a list of kernel parameters used on an NCN, each will denote its default values. If more than one default value is listed, that means the parameter itself is listed on the command line multiple times.

e.g. console is listed on the command line twice, once to enable tty0 and again

to enable serial devices with ttyS0,115200.

Parameters are viewable in four places:

  • /proc/cmdline on any booted Linux server will denote the currently active parameters.
  • /metal/recovery/boot/grub2/grub.cfg will contain boot parameters for disk boots.
  • /var/www/ncn-*/script.ipxe contains boot parameters for PXE boots from the PIT.
  • Cray-BSS contains boot parameters for PXE boots from CSM runtime.

For custom kernel parameters for resizing partitions or controlling other behaviors from CSM: Metal’s dracut, see the following pages:

biosdevname

NCN Type Default Value(s)
All 1

This value determines whether interfaces will use standardized names. Any interface that does not receive a udev rule from ifname or from an RPM package installed in the OS will use a standardized name.

See Consistent Network Device Naming Using biosdevname for more information.

ifname

NCN Type Default Value(s)
All mgmt0:<mac address>
All mgmt1:<mac address>
Kubernetes Masters lan0:<mac address>
Kubernetes Workers hsn0:<mac address>
Kubernetes Workers hsn1:<mac address>
Storage sun0:<mac address>
Storage sun1:<mac address>

This parameter creates a udev rule for a network interface, assigning a bus ID or a MAC address to a name.

  • mgmt* interfaces are used for the management network and are members of bond0.
  • sun* interfaces are used for the storage utility network (SUN) and are members of bond1 and will only exist if more than 2 ports are detected in the PCI bus.
  • hsn* interfaces are used for the high-speed network (HSN) and will only exist on nodes with detectable PCIe cards classified for HSN use.
  • lan* interfaces are used for connections to customer LAN(s) and will only exist if unclassified onboard or PCIe NICs are detected. LANs are cleared for use on Kubernetes masters, lan* interfaces should only be utilized on those nodes.

NOTE The MAC address will be filled in by metal-iPXE during boots from the PIT, or by Cray BSS during boots in runtime.

For more information, see dracut command line’s network parameter definition and the NCN Networking page.

ip

NCN Type Default Value(s)
All mgmt0:dhcp
All *:auto6

This parameter hard codes the DHCP request to go over mgmt0 during boot. The IP received from the DHCPREQUEST will be used to download the NCN image to a local disk when the NCN boots.

This parameter also sets auto6 for any other interface, this is a workaround to ensure the initramFS acknowledges the given interface. In CSM 0.9 and 1.0 despite having ifname set, udev rules were not created for devices unless they had a corresponding ip parameter set. The auto6 value was the safest value to set here that did not disrupt the state of the NCN.

NOTE When an NCN boots using a disk this parameter is not set (ip is removed), disk boots will use the already stored image found in the SquashFS storage.

For more information, see dracut command line’s network parameter definition.

psi

NCN Type Default Value(s)
All 1

This parameter enables pressure stall information from the kernel.

cat /proc/pressure/{cpu,io,memory}

Potential output:

some avg10=0.00 avg60=0.00 avg300=0.00 total=4054991
some avg10=0.00 avg60=0.00 avg300=0.00 total=18417915
full avg10=0.00 avg60=0.00 avg300=0.00 total=18199681
some avg10=0.00 avg60=0.00 avg300=0.00 total=0
full avg10=0.00 avg60=0.00 avg300=0.00 total=0

NOTE If this is unset, the default is 0. The files cpu, io, and memory located at /proc/pressure will be unreadable if this is disabled.

pcie_ports

NCN Type Default Value(s)
All native

Ensures that Linux uses native AER and DPC services.

transparent_hugepage

NCN Type Default Value(s)
All never

This parameter controls the behavior of memory paging with regard to transparent huge pages.

CSM does not want these to be used at all, and disables them by setting this parameter to never.

NOTE Historically, Cray has always set this to never.

console

NCN Type Default Value(s)
All tty0
All ttyS0,115200

iommu

NCN Type Default Value(s)
All pt

This parameter sets the Input-Output Memory Management Unit (IOMMU) to pass-through mode (when set to pt).

This ensures maximum performance when SR-IOV is enabled, telling the operating system to ignore IOMMU for host-only devices (e.g. devices created via SR-IOV).

NOTE This is set whether or not SR-IOV is enabled in the BIOS.

metal.server

This parameter’s value tells the initramFS where to download the kernel, initrd, and SquashFS from.

NCN Type Default Value(s) Context
All http://pit/<hostname> /proc/cmdline
All http://rgw-vip.nmn/$K8S_IMS_IMAGE_ID/rootfs?<auth-token> /proc/cmdline
All http://rgw-vip.nmn/$CEPH_IMS_IMAGE_ID/rootfs?<auth-token> /proc/cmdline
All s3://boot-images/$K8S_IMS_IMAGE_ID/rootfs cray-bss
All s3://boot-images/$CEPH_IMS_IMAGE_ID/rootfs cray-bss

For more information, see dracut-metal-mdsquash’s usage on metal.server.

When the node boots, cray-bss will replace any URL prefixed with s3:// with an http:// URL that includes a pre-signed authorization token.

NOTE This parameter is not set for disk boots because no images need to be downloaded. Instead, the local images will be used.

metal.no-wipe

NCN Type Default Value(s)
All 0
All 1

This parameter’s value is 0 for initial deployments, when metal.no-wipe=0 is set (or when metal.no-wipe is not set at all) the NCN will wipe any existing LVMs, RAIDs, NVME, SAS, and SATA devices.

When this value is set to 1, the wipe function mentioned in the previous paragraph is disabled.

For more information, see dracut-metal-mdsquash’s definition of metal.no-wipe. This parameter gives the administrator some time to cancel the boot before the wipe occurs, that time is controlled by metal.wipe-delay. For more information on metal.wipe-delay, see dracut-metal-mdsquash’s definition of metal.wipe-delay.

NOTE USB Devices are always ignored.

ds

NCN Type Default Value(s)
All nocloud-net;s=http://10.1.1.2:8888/;h=ncn-m002
All nocloud-net;s=http://10.92.100.81:8888/

This parameter tells cloud-init what to use for the data source. The values listed above will vary depending on whether the node is booting from the PIT or from runtime, this is because the server hosting the data source moves in each context.

For more information on the ds=nocloud and ds=nocloud-net, see cloud-init’s data sources NoCloud page.

rootfallback

NCN Type Default Value(s)
All LABEL=BOOTRAID

This parameter tells the initramFS what to use if it is unable to resolve the root filesystem.

NOTE This parameter is actually broken, the BOOTRAID does not contain a full filesystem that the initramFS can switch to. In the event this is needed, an emergency shell will appear.

For more information, see dracut command line’s standard parameter definition.

initrd

NCN Type Default Value(s)
All initrd.img.xz
All initrd

NOTE Runtime uses the name initrd, which hides the fact that the initrd is compressed. Both the initrd used in bootstrap and runtime are xz compressed.

For more information, see the Linux kernel user’s administrator’s guide.

root

NCN Type Default Value(s)
All live:LABEL=SQFSRAID

This parameter tells dracut two things:

  1. We are using the live module for booting images.
  2. Our SquashFS image is on a filesystem with the FSLabel of SQFSRAID

For more information, see dracut command line’s standard parameter definition, and dracut-metal-mdsquash usage.

rd.live.ram

NCN Type Default Value(s)
All 0

This parameter determines whether or not to copy the entire SquashFS image into RAM or not. This is useful when the media resides on a slow I/O device such as a DVD.

For more information, see dracut command line’s booting live images definitions.

rd.writable.fsimg

NCN Type Default Value(s)
All 0

This enables writing to the SquashFS image, this is not always supported nor desired. CSM does not want to enable writing to the image in order to preserve the original image. All changes are written to a persistent OverlayFS instead.

For more information, see dracut command line’s booting live images definitions.

rd.skipfsck

NCN Type Default Value(s)
All 1

This parameter skips the filesystem check when it exists (or is set to 1). This is skipped because it takes extra time during boot and is not always necessary.

For more information, see dracut command line’s standard parameter definition.

rd.live.squashimg

NCN Type Default Value(s)
All filesystem.squashfs

For more information, see dracut command line’s booting live images definitions.

rd.live.dir

NCN Type Default Value(s)
All unset
All $CSM_RELEASE

For more information, see dracut command line’s booting live images definitions.

rd.live.overlay

NCN Type Default Value(s)
All LABEL=ROOTRAID

For more information, see dracut command line’s booting live images definitions.

rd.live.overlay.thin

NCN Type Default Value(s)
All 1

For more information, see dracut command line’s booting live images definitions.

rd.live.overlay.overlayfs

NCN Type Default Value(s)
All 1

For more information, see dracut command line’s booting live images definitions.

rd.live.overlay.reset

NCN Type Default Value(s)
All 0

For more information, see dracut command line’s booting live images definitions.

rd.luks

NCN Type Default Value(s)
Kubernetes Masters exists
Kubernetes Workers 0
Storage exists

When this parameter exists it assumes the value of 1 and enables LUKS usage.

NOTE Kubernetes masters and workers use the same dracut modules, in order to disable dracut-metal-luksetcd on worker nodes this parameter is set to 0. For more information on how dracut-metal-luksetcd uses rd.luks, see its page here.

rd.luks.crypttab

NCN Type Default Value(s)
All 0

For more information, see dracut command line’s definition of LUKS parameters and dracut-metal-luksetcd’s usage.

rd.lvm.conf

NCN Type Default Value(s)
All 0

For more information, see dracut command line’s definition of LVM parameters and dracut-metal-luksetcd’s usage.

rd.lvm

NCN Type Default Value(s)
All 1

Whether or not lvm is enabled in the initramFS.

For more information, see dracut command line’s definition of LVM parameters and dracut-metal-luksetcd’s usage.

rd.auto

NCN Type Default Value(s)
All 1

Enable automatic assembly of special devices like cryptoLUKS, dmraid, mdraid or lvm.

NOTE Any specific setting such as rd.luks=0 will take precedence to rd.auto=1.

For more information, see dracut command line’s standard definition.

rd.md

NCN Type Default Value(s)
All 1

This parameter enables or disables mdraid in the initramFS.

rd.dm

NCN Type Default Value(s)
All 0

This parameter enables or disables dmraid in the initramFS.

NOTE dmraid is not used by the NCNs.

rd.neednet

NCN Type Default Value(s)
All 0

Whether or not the network is necessary for boot.

NOTE This is useful for booting over an NFS or other network share, NCNs set this to 0 because despite downloading a SquashFS the root parameter is set to a disk FSLabel. As such, root is not dependent on the network to come up.

rd.peerdns

NCN Type Default Value(s)
All 0

Whether or not DNS should be resolved from peers.

NOTE This is set to 0 because it is inconsistent and the DNS will differ between boots. Setting this to 0 removes question whether DNS was incorrect or not, if a DHCP lease was received from CSM or PIT services then DNS will work unless core DNS providers are down.

rd.md.waitclean

NCN Type Default Value(s)
All 1

Whether RAID must be clean/synced before use.

NOTE Setting this to 0 will not workaround a dirty RAID, a dirty RAID will cause a boot failure.

rd.multipath

NCN Type Default Value(s)
All 0

Whether or not multipath is used in the initramFS and in the booted OS.

NOTE This will cause undesirable behavior when set to 1 on an NCN.

rd.md.conf

NCN Type Default Value(s)
All 1

Whether or not mdraid should acknowledge any md.conf available in the initramFS.

NOTE This is important to set to 1, otherwise mdraid will not acknowledge our NCN configuration that specifically tells mdraid to not use hostnames for naming RAID devices. That means RAID /dev/md/ devices will use the defined, expected names.

rd.bootif

NCN Type Default Value(s)
All 0

This sets the boot interface.

NOTE This is deprecated in native dracut. NCNs set this to 0 to ensure nothing can be coded to depend on it.

hostname

NCN Type Default Value(s)
All <varies>

Sets the hostname for the node within the initramFS.

rd.net.timeout.carrier

NCN Type Default Value(s)
All 120 (seconds)

The amount of time dracut will wait for a carrier to come up on a requested device.

rd.net.timeout.ifup

NCN Type Default Value(s)
All 120 (seconds)

The amount of time dracut will wait for an interface to establish connectivity if it is requested.

NCN Type Default Value(s)
All 120 (seconds)

The amount of time dracut will wait for an interface to establish a link-up.

rd.net.dhcp.retry

NCN Type Default Value(s)
All 5 (attempts)

How many times DHCP will be attempted before dracut gives up.

NOTE If any ip= argument is set to dhcp (e.g. ip=*:dhcp or ip=net0:dhcp), then dracut will fail if an IP is not provided. By setting an ip= argument to dhcp the user is telling dracut that it is dependent on an IP lease.

rd.net.timeout.ipv6auto

NCN Type Default Value(s)
All 0

The amount of time dracut will wait for an interface using ipv6auto to receive its IPv6 information.

rd.net.timeout.ipv6dad

NCN Type Default Value(s)
All 0

The amount of time dracut will wait for an interface using ipv6auto to receive its IPv6 DAD information.

append

NCN Type Default Value(s)
All exists

Deprecated/not-used.

NOTE This parameter exists as a no-op, it is used for sed to key off of but it does nothing by itself.

nosplash

NCN Type Default Value(s)
All exists

Disables splash screens, if they are present anywhere.

quiet

NCN Type Default Value(s)
All exists

Minimize the output from the initramFS to only stderr.

NOTE Setting rd.info will override this, and emit stdout to the console as well.

crashkernel

NCN Type Default Value(s)
All 360M

The amount of memory reserved in the event of a crash to run dump tools.

This must be larger than the size of the kdump initrd located in /boot.

log_buf_len

NCN Type Default Value(s)
All 1

Size of the kernel’s internal log buffer by powers of 2.

split_lock_detect

NCN Type Default Value(s)
All off

Intel has added Split Lock Detection to its 10th generation CPUs and this affects the Castle and Wisteria platforms which will be delivered in the Alice release. The Linux kernel has Split Lock Detect enabled by default, but it can be disabled on a host by adding the kernel parameter, split_lock_detect=off to the kernel command line. See this ticket for more detail.

rd.retry

NCN Type Default Value(s)
All 10

How long dracut should retry the initqueue to configure devices (in seconds). See the misc section of dracut.

rd.shell

NCN Type Default Value(s)
All exists

This parameter ensures that if the initramFS were to fail that a shell be created for an administrator to investigate and/or provide triage information.

xname

NCN Type Default Value(s)
All <varies>

This value sets the xname for the node, detailing the geolocation of the node.

Versioning

CSM Release Kernel Version Kernel Change Rationale
CSM 0.9.0 (Shasta v1.4.0) 5.3.18-24.49.2 Initial
CSM 0.9.2 (Shasta v1.4.1) 5.3.18-24.49.2
CSM 0.9.3 (Shasta v1.4.2) 5.3.18-24.49.2
CSM 0.9.3 5.3.18-24.75.3 Proactive update
CSM 0.9.4 5.3.18-24.75.3
CSM 0.9.5 5.3.18-24.75.3
CSM 0.9.6 5.3.18-24.75.3
CSM 1.0.0 5.3.18-24.75.3
CSM 1.0.1 (Shasta v1.5.0) 5.3.18-24.75.3
CSM 1.0.10 5.3.18-24.75.3
CSM 1.0.11 5.3.18-24.99.1 CVE-2021-4034
CSM 1.2.0 5.3.18-150300.59.43.1 CVE-2022-0185
CSM 1.2.1 5.3.18-150300.59.43.1 CVE-2022-0185
CSM 1.2.2 5.3.18-150300.59.43.1
CSM 1.3.0 5.3.18-150300.59.87.1 CVE-2022-33981
CSM 1.3.1 5.3.18-150300.59.87.1
CSM 1.4.0 5.14.21-150400.24.38.1.25440.1.PTF.1204911 SLES-15-SP4 upgrade and SUSE patch (case #00502283)