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Howto create VM image

This document describe how the virtual machine (VM) image for the XDP-tutorial were created.

Installing needed packages for XDP-tutorial

The Ansible setup in directory ansible/ is used to define and install the needed software packages. This were used on the image after below setup.

Downloading images

Here we download a predefined “cloud” image, and update it to suit the tutorial.

Finding some alternative images to download here:

Specifically downlaod the: “Cloud Base qcow2 image” (size 294M)

Place a copy in: var/lib/libvirt/images

  • with filename: F29-xdp-tutorial.qcow2.

Initial setup for cloud-init

Use of the cloud image is annoying, because it requires creating a special CDROM image to reconfigure. After reboots it still want to do some cloud-init, which either requires mounting below CDROM-image or disabling cloud-init via cmdline: touch /etc/cloud/cloud-init.disabled

Create: cloud-init.iso

As describe here, these cloud images need/tries to fetch some setup info. We need to supply this, else you cannot login to them. This is supplied by creating a special crafted ISO image.

Create two files:

cat > meta-data << EOF
instance-id: iid-local01
local-hostname: xdp-tutorial
EOF

cat > user-data << EOF
#cloud-config
password: xdptut
ssh_pwauth: True
chpasswd: { expire: False }

ssh_authorized_keys:
  - ssh-rsa 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 netoptimizer@github
EOF

Create the ISO file that the images can use as CDROM drive:

genisoimage -output cloud-init.iso -volid cidata -joliet -rock user-data meta-data

Then copy init.iso into /var/lib/libvirtd/images as well (if you already have an non-functional cloud-image, you can connect this images as virtual-CDROM drive).

sudo cp cloud-init.iso /var/lib/libvirt/images/

Initial: Import/use VM-image

Create via virt-install

You can create a new libvirt machine, that use this image, from the command line using virt-install.

Notice these two files must exist:

  • /var/lib/libvirt/images/F29-xdp-tutorial.qcow2
  • /var/lib/libvirt/images/cloud-init.iso

Use virt-install:

sudo virt-install --name F29-xdp-tutorial \
--description 'Fedora 29 - XDP-tutorial' \
--ram 2048 \
--vcpus 2 \
--disk path=/var/lib/libvirt/images/F29-xdp-tutorial.qcow2 \
--cdrom  /var/lib/libvirt/images/cloud-init.iso \
--os-type linux \
--os-variant fedora29 \
--network bridge=virbr0 \
--graphics vnc,listen=127.0.0.1,port=5901 \
--noautoconsole

Another important detail: If the machines doesn’t give you a console after rebooting, then you likely need to (again) add the CDROM drive with the cloud-init.iso (/var/lib/libvirt/images/cloud-init.iso). This can be done via virt-manager. You can also disable “cloud-init” via command line: sudo touch /etc/cloud/cloud-init.disabled

Default user+password

End-result: A virtual machine with:

  • Username: fedora
  • Password: xdptut

This Fedora-Cloud image have a 10 sec. delay when logging in as root, remove that via editing root.ssh/authorized_keys.

Disk capacity

Increasing VM disk capacity

The remaining disc capacity is getting low, it will be unfortunate if this disrupt the tutorial. Thus, we resize the VM disk. First shutdown the VM.

Following this blogpost we resize disk via commands.

On host-OS machine:

cd /var/lib/libvirt/images/
qemu-img resize F29-xdp-tutorial.qcow2 +2G
qemu-img info   F29-xdp-tutorial.qcow2

Now power up the VM, login as root (or use sudo) for next commands on VM:

echo ", +" | sfdisk -N 1 /dev/vda --no-reread
partprobe
resize2fs /dev/vda1

Reduce VM image size

Before uploading, use the tool virt-sparsify to reduce disk capacity used by VM image. And afterwards also compress image, to reduce download size.

Extra manual changes

Cloned some git trees in user ‘fedora’ home directory.

List of git trees:

stow

Use stow to easier keep track of manually installed packages under: /usr/local/

Some manual setup (TODO move this to ansible):

Note, ansible-setup have already added /usr/local/lib to ldconfig.

pahole

Until LLVM 8.0.0 gets released, we can use pahole to create the BTF-info into in the BPF-ELF files. The on Fedora 29 the package ‘dwarves’ that contain pahole is too old to have the needed BTF-features (avail in version 1.12). Thus, we need to build it ourselves.

Building pahole:

cd ~/git/pahole
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=/usr/local/stow/pahole-git01 -D__LIB=lib ..
make

Stow part of the setup:

cd /usr/local/stow/
stow pahole-git01
sudo ldconfig

Kernel samples/bpf/

Uploaded a compiled version of kernel samples/bpf/ directory. The xdp_monitor tool could come in handy for participants.