How to enable consistent network device names when creating a whole disk image

Solution In Progress - Updated -

Environment

  • Red Hat OpenStack Platform 16.2
  • Red Hat Enterprise Linux 8.2 Update KVM Guest Image

Issue

  • When creating a full disk image and deploying the overcloud, the NIC name is set as ethX.
  • net.ifnames=0 is set in /etc/default/grub
# virt-cat -a overcloud-hardened-uefi-full.qcow2 /etc/default/grub
GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8 no_timer_check net.ifnames=0 crashkernel=auto"     <==(*)
GRUB_TIMEOUT=0
GRUB_ENABLE_BLSCFG=true
GRUB_DEVICE=LABEL=img-rootfs
GRUB_DISABLE_LINUX_UUID=true
GRUB_TIMEOUT=5
GRUB_TERMINAL="serial console"
GRUB_GFXPAYLOAD_LINUX=auto
GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,115200 no_timer_check nofb nomodeset vga=normal console=tty0 console=ttyS0,115200 audit=1 nousb"
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"

Resolution

  • net.ifnames=0 can be removed from GRUB_CMDLINE_LINUX by specifying the interface-names element when creating the image.

overcloud-hardened-images-uefi-python3.yaml:

disk_images:
  -
    imagename: overcloud-hardened-uefi-full
    type: qcow2
    elements:
      - openvswitch
...
      - openssh
      - disable-nouveau
      - interface-names                        <==(*)
    packages:
      - python3-psutil
...

Root Cause

  • The current RHEL8 KVM image has net.ifnames=0 set in the Kernel Args, which causes the NIC to be configured with ethX in the environment after image deployment.
  • Due to concerns about the impact of net.ifnames=0, tripleo has been modified to remove net.ifnames=0 from the Kernel Args when generating the image.

Diagnostic Steps

  • After creating a whole-disk image using the interface-names element, it is able to verify with virt-cat that net.ifnames=0 is not set in /etc/default/grub in the image.
[stack@imagebuild ~]$ cat overcloud-hardened-images-uefi-python3.yaml
disk_images:
  -
    imagename: overcloud-hardened-uefi-full
    type: qcow2
    elements:
      - openvswitch
...
      - openssh
      - disable-nouveau
      - interface-names                        <==(*)
    packages:
      - python3-psutil
...

[root@imagebuild ~]# virt-cat -a /home/stack/overcloud-hardened-uefi-full.qcow2 /etc/default/grub
GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8 no_timer_check  crashkernel=auto"
GRUB_TIMEOUT=0
GRUB_ENABLE_BLSCFG=true
GRUB_DEVICE=LABEL=img-rootfs
GRUB_DISABLE_LINUX_UUID=true
GRUB_TIMEOUT=5
GRUB_TERMINAL="serial console"
GRUB_GFXPAYLOAD_LINUX=auto
GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,115200 no_timer_check nofb nomodeset vga=normal console=tty0 console=ttyS0,115200 audit=1 nousb"
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"

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