Provisioning disks

As a tech preview, Warewulf provides structures to define disks, partitions, and file systems. These structures can generate a configuration for Ignition to provision partitions and file systems dynamically on cluster nodes, or with sfdisk, mkfs, and mkswap during boot.

Ignition can, for example, create swap partitions or /scratch file systems.

Note

Warewulf is not currently able to provision the node image onto an explicitly provisioned root file system.

Requirements

Partition and file system creation requires both ignition and sgdisk to be installed in the image.

Rocky Linux

dnf install ignition gdisk

Note

Packages for Ignition are not currently available for Rocky Linux 8, but it is available for Rocky Linux 9 as part of “appstream.”

openSuse Leap

zypper install ignition gptfdisk

Disks and partitions

A node or profile can have several disks. Each disk is identified by the path to its block device. Each disk holds a map to its partitions and a bool switch to indicate if an existing, non-matching partition table should be overwritten.

Each partition is identified by its label. The partition number can be omitted, but specifying it is recommended as Ignition may fail without it. Partition sizes should also be set (specified in MiB), except for the last partition: if no size is given, the maximum available size is used. Each partition has the switches should_exist and wipe_partition_entry which control the partition creation process. When omitting a partition number the wipe_partition_entry should be true, as this allows ignition to replace the existing partition.

wwctl node set n1 \
  --diskname /dev/vda --diskwipe \
  --partname scratch --partcreate --partnumber 1

File systems

File systems are identified by their underlying block device, preferably using the /dev/by-partlabel format. Except for a swap partition, an absolute path for the mount point must be specified for each file system. Depending on the image used, valid formats are btrfs, ext3, ext4, and xfs. Each file system has the switch wipe_filesystem to control whether an existing file system is wiped.

wwctl node set n1 \
  --diskname /dev/vda --partname scratch \
  --fsname scratch --fsformat btrfs --fspath /scratch

Boot-time configuration

Ignition uses systemd, as the underlying sgdisk command relies on dbus notifications.

1. ignition-disks-ww4.service uses Ignition to create the specified partitions and file systems.

2. ww4-disks.target depends on a matching .mount unit for each mounted file system.

3. Each .mount creates the necessary mount points in the root file system and mounts the provisioned file systems during boot.

These services and mount units are generated by the ignition overlay and depend on the existence of the file /warewulf/ignition.json, also generated by the ignition overlay.

Example disk configurations

This command formats a btrfs file system on a “scratch” partion of “vda” and mounts it at /scratch.

wwctl node set n1 \
  --diskname /dev/vda --diskwipe \
  --partname scratch --partcreate --partnumber 1 \
  --fsname scratch --fsformat btrfs --fspath /scratch

This command adds a swap partition to the “vda” disk.

wwctl node set n1 \
  --diskname /dev/vda \
  --partname swap --partsize=1024 --partnumber 2 \
  --fsname swap --fsformat swap --fspath swap

Re-using or wiping disks

For empty disks the desired configuration is created and the filesystems are mounted. If partitions or file systems already exist on the disk, ignition tries to reuse existing file systems by default.

To ignore existing file systems and provision fresh file systems on each boot, specify the --fswipe` flag for that filesystem, and --diskwipe for the disk, as necessary.

If you would like to re-use existing partitions but want to replace existing file systems once, you may

• wipe the existing data with tools like wipefs or dd [1]; or

• set the --fswipe flag and remove it after one reboot.

[1]

With wipefs you have to remove the filesystem and parition information. E.g., use wipefs -fa /dev/vda* to remove all file system information and partition information.

See the upstream ignition documentation for additional information.

Provision to disk

New in Warewulf v4.6.2

As a tech preview, the Warewulf two-stage boot process can provision the node image to local storage.

Warning

This functionality is a technology preview and should be used with care. Pay specific attention to wipeFilesytem and similar settings.

Note

Warewulf doesn’t install a bootloader to the disk or add UEFI entries. Nodes still request an image and configuration from the Warewulf server on every boot.

Note

While provisioning to disk should be possible during a single-stage boot, not all features are available:

• Warewulf does not perform hardware detection to ensure that necessary kernel modules are loaded prior to init.

• Warewulf does not load udev to ensure that /dev/disk/by-* symlinks are available prior to init.

With Ignition

Warewulf needs a prepared file system to deploy the image to. Warewulf can provision this file system using Ignition. To use Ignition, include ignition in your system overlay. The ignition overlay provisions disks during init and, optionally, during the first stage of a two-stage boot. This allows the root file system to be provisioned before the image is loaded.

wwctl node set wwnode1 \
  --diskname /dev/vda --diskwipe \
  --partname rootfs --partcreate --partnumber 1 \
  --fsname rootfs --fsformat ext4 --fspath /

In order to allow Dracut to provision the disk, partition, and file system, Ignition must be included in the Dracut image.

wwctl image exec rockylinux-9 -- /usr/bin/dracut --force --no-hostonly --add wwinit --add ignition --regenerate-all

The necessary file system may alternatively be prepared out-of-band.

With sfdisk and mkfs

Systems that do not have access to Ignition (e.g., Rocky Linux 8) can provision the root file system using a combination of sfdisk and mkfs. To use them, include sfdisk and mkfs in your system overlay. The sfdisk and mkfs overlays provision disk and file systems during the first stage of a two-stage boot. This allows the root file system to be provisioned before the image is loaded.

Configure the sfdisk and mkfs overlays using resources:

wwctl node set wwnode1 \
  --diskname /dev/vda --diskwipe \
  --partname rootfs --partcreate --partnumber 1 \
  --fsname rootfs --fsformat ext4 --fspath /

In order to allow Dracut to provision the disk, partition, and file system, some additional commands must be included in the Dracut image, depending on which functionality is used:

• sfdisk: writes the partition table

  • blockdev: used to re-read the partition table after writing

  • udevadm: used to trigger udev events after writing the partition table

• mkfs: formats file systems (may also require file-system-specific commands like mkfs.ext4)

  • mkfs.ext4, mkfs.btrfs, etc: used by mkfs to format specific file systems

  • wipefs: used to determine if a file system already exists

wwctl image exec rockylinux-8 -- /usr/bin/dracut --force --no-hostonly \
  --add wwinit \
  --install sfdisk \
  --install blockdev \
  --install udevadm \
  --install mkfs \
  --install mkfs.ext4 \
  --install wipefs \
  --regenerate-all

Configuring the root device

Set the desired storage device for the node image using the --root parameter.

wwctl node set wwnode1 --root /dev/disk/by-partlabel/rootfs