---
title: Early experiences with PXE (net-)boot of KVM VMs on Ubuntu for s390x
description: This article originally appeared on the Ubuntu On Big Iron blog This
  article mainly assumes that an Ubuntu Server 17.10 (artful) is installed in LPAR.
  Ubuntu 17.10 comes with a qemu-kvm version that is new enough to act as a KVM host
  that also allows to PXE netboot KVM virtual machines. Any potentially different
  or  […]
url: https://canonical.com/blog/early-experiences-with-pxe-net-boot-of-kvm-vms-on-ubuntu-for-s390x?format=md
---

1. [Blog](https://canonical.com/blog)
2. Article

---

[Canonical](https://canonical.com/blog/author/canonical "More about Canonical")

20 December 2017

# Early experiences with PXE (net-)boot of KVM VMs on Ubuntu for s390x

[IBM](https://canonical.com/blog/tag/ibm)
[kvm](https://canonical.com/blog/tag/kvm)
[mainframe](https://canonical.com/blog/tag/mainframe)
[s390x](https://canonical.com/blog/tag/s390x)
[Virtual Machines](https://canonical.com/blog/tag/virtual-machines)

---

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*This article originally appeared on the [Ubuntu On Big Iron blog](http://ubuntu-on-big-iron.blogspot.com/2017/12/pxe-netboot-kvm-s390x.html)*

This article mainly assumes that an Ubuntu Server 17.10 (artful) is installed in LPAR.

Ubuntu 17.10 comes with a qemu-kvm version that is new enough to act as a KVM host that also allows to PXE netboot KVM virtual machines.

Any potentially different or additional steps for Ubuntu Server 16.04(.x) are marked in *italics*.

PXE boot will only work on Ubuntu 16.04 if the qemu-kvm package from the Pike Ubuntu Cloud Archive (UCA) is used.

## Prepare virtualization packages

*Note:
On Ubuntu 16.04.x qemu-kvm from the Pike Ubuntu Cloud Archive (UCA) need to be installed.
The Pike Cloud Archive can be enabled like this:*

```

$ sudo add-apt-repository cloud-archive:pike
$ sudo apt update
```

On Ubuntu 17.10 (or higher) just install the default qemu-kvm and related packages with:

`$ sudo apt install -qq -y libvirt-daemon-system qemu-kvm`

The just installed packages modify the underlying environment, hence it’s recommended to quickly logout and login again to make the changes take effect.

## Prepare s390 netboot ROM

```

$ sudo apt -y -qq install ubuntu-dev-tools

$ pull-lp-source qemu artful
pull-lp-source: Downloading qemu version 1:2.10+dfsg-0ubuntu3.1
...

$ sudo cp qemu-2.10+dfsg/pc-bios/s390-netboot.img /usr/share/qemu/
```

## Prepare a tftp server

Now a tftp server is needed for PXE netboot, so let’s install and configure tftp:

```

$ sudo apt -y -qq install tftpd xinetd tftp
...
$ cat << EOF | sudo tee /etc/xinetd.d/tftp
service tftp
{
 protocol        = udp
 port            = 69
 socket_type     = dgram
 wait            = yes
 user            = nobody
 server          = /usr/sbin/in.tftpd
 server_args     = /srv/tftp
 disable         = no
}
EOF
```

Create the tftp folder, copy over the pxelinux.0 file, adjust the folder options and (re-)start the service:

```

$ sudo mkdir -p /srv/tftp
$ sudo chmod -R 777 /srv/tftp
$ sudo chown -R nobody: /srv/tftp
$ sudo systemctl restart xinetd
```

By now you should be able to check if tftp is listening to your local port 69 on the default libvirt networks IP of your host:

```

$ nc -uvz 192.168.122.1 69
Connection to 10.245.236.13 69 port [udp/tftp] succeeded!
```

## Prepare libvirt network to provide PXE

Since we have slightly different network needs, we will modify the default network a bit,
which was created for you on install. In this step we add the lines in **bold**:

It's not too bad to do a quick backup of the virtual network configuration at the beginning:

`$ virsh net-dumpxml default > net-default.xml`

Now do the needed tftp and bootp modifications:

```

$ virsh net-edit default
<network>
 <name>default</name>
 <uuid>cfa3d2de-4c67-4f8f-91eb-69502e59e64d</uuid>
 <forward mode='nat'/>
 <bridge name='virbr0' stp='on' delay='0'/>
 <mac address='52:54:00:08:6f:33'/>
 <ip address='192.168.122.1' netmask='255.255.255.0'>
 <strong><tftp root='/srv/tftp'/></strong>
  <dhcp>
   <range start='192.168.122.2' end='192.168.122.254'/>
   <strong><bootp file='pxelinux.0' server='192.168.122.1'/></strong>
  </dhcp>
 </ip>
</network>
</pre>
```

And restart the virtual network again:

```

$ virsh net-destroy default
Network default destroyed

$ virsh net-start default
Network default started
```

## Prepare netboot image

Before we can perform a PXE netboot, a 'pxelinux.0' netboot image is needed.
We will now create a pxelinux.0 file that is based on the Ubuntu 16.04.3 (xenial) installer.

Now, download the latest xenial installer files (kernel and initrd):

```

$ wget --quiet http://ports.ubuntu.com/ubuntu-ports/dists/xenial-updates/main/installer-s390x/current/images/generic/kernel.ubuntu http://ports.ubuntu.com/ubuntu-ports/dists/xenial-updates/main/installer-s390x/current/images/generic/initrd.ubuntu
```

And create a pxelinux.0 file out of these kernel and initrd installer files:For the PXE image creation a separate tool is needed from the s390-tools collection:

```

$ git clone --quiet https://github.com/ibm-s390-tools/s390-tools.git
...
$ ./s390-tools/netboot/mk-s390image kernel.ubuntu -r initrd.ubuntu pxelinux.0
$ ll pxelinux.0
-rw-rw-r-- 1 ubuntu ubuntu 15346314 Dec  5 05:12 pxelinux.0
$ sudo cp pxelinux.0 /srv/tftp
$ sudo chmod -R 777 /srv/tftp
$ sudo chown -R nobody: /srv/tftp
```

It's now time for a little download test:

```

$ cd /tmp/

$ echo 'get pxelinux.0' | tftp 192.168.122.1

tftp> Received 15453177 bytes in 0.3 seconds
 $ cd -
```

## Prepare guest definition

Now proceed with the creation of a KVM virtual machine definition for the PXE netboot VM:

```

$ cat << EOF > netboot.xml
<domain type='kvm'>
 <name>netboot</name>
 <memory unit='KiB'>2097152</memory>
 <vcpu placement='static'>1</vcpu>
 <os>
  <type arch='s390x' machine='s390-ccw-virtio-xenial'>hvm</type>
  <boot dev='network'/>
 </os>
<devices>
 <emulator>/usr/bin/kvm</emulator>
 <disk type='file' device='disk'>
  <driver name='qemu' type='qcow2'/>
  <source file='/var/lib/libvirt/images/netboot.qcow2'/>
  <target dev='vda' bus='virtio'/>
 </disk>
 <interface type='network'>
  <source network='default'/>
  <model type='virtio'/>
 </interface>
 <console type='pty'>
 <target type='sclp' port='0'/>
  </console>
 </devices>
</domain>
EOF
```

Let's also quickly create a virtual disk that is already part of the VM definition above:

```

$ sudo qemu-img create -f qcow2 /var/lib/libvirt/images/netboot.qcow2 5G
Formatting '/var/lib/libvirt/images/netboot.qcow2', fmt=qcow2 size=5368709120 cluster_size=65536 lazy_refcounts=off refcount_bits=16
```

And now define the virtual machine named 'netboot':

```

$ virsh define netboot.xml
Domain netboot defined from netboot.xml
```

Finally start the netboot guest to prove that PXE netboot is generally working:

```

$ virsh start netboot --console
Domain netboot started
Connected to domain netboot
Escape character is ^]
  Using MAC address: 52:54:00:fa:01:01
                                        Requesting information via DHCP: done
                                                                               Using IPv4 address: 192.168.122.217
                                    Requesting file "pxelinux.0" via TFTP from 192.168.122.1
              Receiving data:  14986 KBytes
                                             TFTP: Received pxelinux.0 (14986 KBytes)
     Network loading done, starting kernel...
                                             [    0.395926] Initializing cgroup subsys cpuset
[    0.395929] Initializing cgroup subsys cpu
[    0.395930] Initializing cgroup subsys cpuacct
[    0.395933] Linux version 4.4.0-96-generic (buildd@z13-009) (gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) ) #119-Ubuntu SMP Tue Sep 12 14:59:56 UTC 2017 (Ubuntu 4.4.0-96.119-generic 4.4.83)
[    0.395937] setup: Linux is running under KVM in 64-bit mode
...
[    0.659971] AppArmor: AppArmor sha1 policy hashing enabled
[    0.659975] ima: No TPM chip found, activating TPM-bypass!

  ┌──────────────────┤ [!!] Configure the network device ├──────────────────┐
  │                                                                         │
  │ Please choose the type of your primary network interface that you       │
  │ will need for installing the Debian system (via NFS or HTTP). Only      │
  │ the listed devices are supported.                                       │
  │                                                                         │
  │ Network device type:                                                    │
  │                                                                         │
  │  ctc: Channel to Channel (CTC) or ESCON connection                      │
  │  qeth: OSA-Express in QDIO mode / HiperSockets                          │
  │  iucv: Inter-User Communication Vehicle - available for VM guests       │
  │  virtio: KVM VirtIO                                                     │
  │                                                                         │
  │                                                                │
  │                                                                         │
  └─────────────────────────────────────────────────────────────────────────┘

```

For now let's leave the VM's console via Ctrl+]

`$`

## The same again but with Preseeds

### Prepare preseed

Okay, this first virtual machine was able to netboot into the default installer - but that's just the first step.
The second step is to combine this with a non-interactive preseed installation.

To do so download an example pressed file (like [this](https://wiki.ubuntu.com/S390X/InstallationGuide/AutomatedInstallsWithPreseed?action=AttachFile&do=get&target=preseed_kvm.cfg) - rename it to 'preseed.cfg') and store it locally in the tftp directory:

```
$ wget --quiet "https://wiki.ubuntu.com/S390X/InstallationGuide/AutomatedInstallsWithPreseed?action=AttachFile&do=get⌖=preseed_kvm.cfg" -O /srv/tftp/preseed.cfg
```

Do another quick check if preseed.cfg is reachable via tftp:

```

$ cd /tmp
/tmp$ echo 'get preseed.cfg' | tftp 192.168.122.1
tftp> Received 699 bytes in 0.0 seconds
$ cd -
```

## Prepare pxe config to map to preseed config

A pxelinux.cfg/default configuration file need to be created as well - just to be able to pass over the kernel parameters for preseed installation.

```

$ sudo mkdir -p /srv/tftp/pxelinux.cfg
$ cat << EOF | sudo tee /srv/tftp/pxelinux.cfg/default
kernel kernel.ubuntu
initrd initrd.ubuntu
append auto=true priority=critical url=tftp://192.168.122.1/preseed.cfg s390-netdevice/choose_networktype=virtio netcfg/disable_dhcp=false netcfg/get_hostname=netboot-preseed netcfg/get_domain=mydomain.com network-console/password=pass4inst network-console/start=true
EOF
```

Now some additional tools/packages are needed to generate a general pxelinux.0 file:

```

$ sudo apt install -y -qq kexec-tools gcc make
$ cd s390-tools/netboot
$ make -f Makefile.pxelinux.0
$ mv /srv/tftp/pxelinux.0 /srv/tftp/pxelinux.0.installer
$ ./s390-tools/netboot/mk-s390image ./kernel.ubuntu pxelinux.0
```

Now we make all this available to PXE boot:

- the new pxelinux.0 that will read the initial config

- the kernel and initrd to be loaded from there and to kexec into

```

$ cp pxelinux.0 /srv/tftp/pxelinux.0
 $ cd -
$ cp initrd.ubuntu /srv/tftp/
$ cp kernel.ubuntu /srv/tftp/
$ sudo chmod -R 777 /srv/tftp
$ sudo chown -R nobody: /srv/tftp
```

## Create second VM

Now define a second guest named 'netboot-preseed' for the PXE netboot initiated non-interactive preseed installation on KVM s390x.
It will be done based on the previous example, hence we only need to adjust some names:

`$ sed -e 's/netboot/netboot-preseed/g' netboot.xml > netboot-preseed.xml`

Again create the virtual disk - in this case really needed, because the installation should complete:

```
$ sudo qemu-img create -f qcow2 /var/lib/libvirt/images/netboot-preseed.qcow2 5G
```

Now define that second VM:

```

$ virsh define netboot-preseed.xml
Domain netboot-preseed defined from netboot-preseed.xml
```

Now start this second VM:

```

$ virsh start netboot-preseed --console
Domain netboot-preseed started
Connected to domain netboot-preseed
Escape character is ^]
  Using MAC address: 52:54:00:fa:4d:4d
                              Requesting information via DHCP:  010
...
                              Requesting information via DHCP: done
                                                                               Using IPv4 address: 192.168.122.213
                                    Requesting file "pxelinux.0" via TFTP from 192.168.122.1
              Receiving data:  14986 KBytes
                                             TFTP: Received pxelinux.0 (14986 KBytes)
     Network loading done, starting kernel...
                                             [    0.394899] Initializing cgroup subsys cpuset
[    0.394902] Initializing cgroup subsys cpu
[    0.394903] Initializing cgroup subsys cpuacct
[    0.394907] Linux version 4.4.0-96-generic (buildd@z13-009) (gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) ) #119-Ubuntu SMP Tue Sep 12 14:59:56 UTC 2017 (Ubuntu 4.4.0-96.119-generic 4.4.83)
[    0.394912] setup: Linux is running under KVM in 64-bit mode

...
can't open /dev/tty3: No such device or address
can't open /dev/tty2: No such device or address
can't open /dev/tty4: No such device or address  ⇐ just ignore these lines !
...
 Finishing the installation
  │                                   95%                                   │
The system is going down NOW!
Sent SIGTERM to all processes device or address
Sent SIGKILL to all processes device or
$
```

The above was the post install shutdown, last task is to adjust the boot order (to not install again):

```
$ virsh edit netboot
```

and change:

```
    <boot dev='network'/>
```

to:

```
    <boot dev='hd'/>
```

and to restart - this time from disk:

No do a final restart of the VM and have fun:

```

$ virsh start netboot-preseed --console
[...]
netboot-preseed login: _
```

At this stage two KVM virtual machine are in use. The first one ('netboot') was netboot-ed and landed in a regular interactive d-i installation; the second ('netboot-preseed') was again net-booted, but then performed a non-interactive d-i preseed installation.

### References:

* <https://github.com/ibm-s390-tools/s390-tools/tree/master/netboot>
* <http://www.syslinux.org/wiki/index.php?title=PXELINUX>
* <https://help.ubuntu.com/community/Installation/QuickNetboot>
* <https://wiki.qemu.org/Features/S390xNetworkBoot>

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