Configuring PXE and iPXE¶

DHCP server setup¶

A DHCP server is required by PXE/iPXE client. You need to follow steps below.

Set the [dhcp]/dhcp_provider to neutron in the Bare Metal Service’s configuration file (/etc/ironic/ironic.conf):

Note

Refer Configure tenant networks for details. The dhcp_provider configuration is already set by the configuration defaults, and when you create subnet, DHCP is also enabled if you do not add any dhcp options at “openstack subnet create” command.
Enable DHCP in the subnet of PXE network.
Set the ip address range in the subnet for DHCP.

Note

Refer Configure the Networking service for bare metal provisioning for details about the two precedent steps.
Connect the openstack DHCP agent to the external network through the OVS bridges and the interface eth2.

Note

Refer Configure the Networking service for bare metal provisioning for details. You do not require this part if br-int, br-eth2 and eth2 are already connected.
Configure the host ip at br-eth2. If it locates at eth2, do below:
```
ip addr del 192.168.2.10/24 dev eth2
ip addr add 192.168.2.10/24 dev br-eth2
```
Note

Replace eth2 with the interface on the network node which you are using to connect to the Bare Metal service.

TFTP server setup¶

In order to deploy instances via PXE, a TFTP server needs to be set up on the Bare Metal service nodes which run the ironic-conductor.

Make sure the tftp root directory exist and can be written to by the user the ironic-conductor is running as. For example:
```
sudo mkdir -p /tftpboot
sudo chown -R ironic /tftpboot
```

Install tftp server:

Ubuntu:

sudo apt-get install xinetd tftpd-hpa

RHEL7/CentOS7:

sudo yum install tftp-server xinetd

Fedora:

sudo dnf install tftp-server xinetd

SUSE:

sudo zypper install tftp xinetd

Using xinetd to provide a tftp server setup to serve /tftpboot. Create or edit /etc/xinetd.d/tftp as below:

service tftp
{
  protocol        = udp
  port            = 69
  socket_type     = dgram
  wait            = yes
  user            = root
  server          = /usr/sbin/in.tftpd
  server_args     = -v -v -v -v -v --map-file /tftpboot/map-file /tftpboot
  disable         = no
  # This is a workaround for Fedora, where TFTP will listen only on
  # IPv6 endpoint, if IPv4 flag is not used.
  flags           = IPv4
}

and restart the xinetd service:

Ubuntu:

sudo service xinetd restart

Fedora/RHEL7/CentOS7/SUSE:

sudo systemctl restart xinetd

Note

In certain environments the network’s MTU may cause TFTP UDP packets to get fragmented. Certain PXE firmwares struggle to reconstruct the fragmented packets which can cause significant slow down or even prevent the server from PXE booting. In order to avoid this, TFTPd provides an option to limit the packet size so that it they do not get fragmented. To set this additional option in the server_args above:

--blocksize <MAX MTU minus 32>

Create a map file in the tftp boot directory (/tftpboot):

echo 're ^(/tftpboot/) /tftpboot/\2' > /tftpboot/map-file
echo 're ^/tftpboot/ /tftpboot/' >> /tftpboot/map-file
echo 're ^(^/) /tftpboot/\1' >> /tftpboot/map-file
echo 're ^([^/]) /tftpboot/\1' >> /tftpboot/map-file

UEFI PXE - Grub setup¶

In order to deploy instances with PXE on bare metal nodes which support UEFI, perform these additional steps on the ironic conductor node to configure the PXE UEFI environment.

Install Grub2 and shim packages:

Ubuntu (18.04LTS and later):

sudo apt-get install grub-efi-amd64-signed shim-signed

RHEL7/CentOS7:

sudo yum install grub2-efi shim

Fedora:

sudo dnf install grub2-efi shim

SUSE:

sudo zypper install grub2-x86_64-efi shim

Copy grub and shim boot loader images to /tftpboot directory:

Ubuntu (18.04LTS and later):

sudo cp /usr/lib/shim/shimx64.efi.signed /tftpboot/bootx64.efi
sudo cp /usr/lib/grub/x86_64-efi-signed/grubnetx64.efi.signed /tftpboot/grubx64.efi

Fedora:

sudo cp /boot/efi/EFI/fedora/shim.efi /tftpboot/bootx64.efi
sudo cp /boot/efi/EFI/fedora/grubx64.efi /tftpboot/grubx64.efi

RHEL7/CentOS7:

sudo cp /boot/efi/EFI/centos/shim.efi /tftpboot/bootx64.efi
sudo cp /boot/efi/EFI/centos/grubx64.efi /tftpboot/grubx64.efi

SUSE:

sudo cp /usr/lib64/efi/shim.efi /tftpboot/bootx64.efi
sudo cp /usr/lib/grub2/x86_64-efi/grub.efi /tftpboot/grubx64.efi

Create master grub.cfg:

Ubuntu: Create grub.cfg under /tftpboot/grub directory:
```
GRUB_DIR=/tftpboot/grub
```
Fedora: Create grub.cfg under /tftpboot/EFI/fedora directory:
```
GRUB_DIR=/tftpboot/EFI/fedora
```
RHEL7/CentOS7: Create grub.cfg under /tftpboot/EFI/centos directory:
```
GRUB_DIR=/tftpboot/EFI/centos
```
SUSE: Create grub.cfg under /tftpboot/boot/grub directory:
```
GRUB_DIR=/tftpboot/boot/grub
```
Create directory GRUB_DIR:
```
sudo mkdir -p $GRUB_DIR
```
This file is used to redirect grub to baremetal node specific config file. It redirects it to specific grub config file based on DHCP IP assigned to baremetal node.
```
set default=master
set timeout=5
set hidden_timeout_quiet=false

menuentry "master"  {
configfile /tftpboot/$net_default_mac.conf
}
```
Change the permission of grub.cfg:
```
sudo chmod 644 $GRUB_DIR/grub.cfg
```
Update the bare metal node with boot_mode:uefi capability in node’s properties field. See Boot mode support for details.
Make sure that bare metal node is configured to boot in UEFI boot mode and boot device is set to network/pxe.

Note

Some drivers, e.g. ilo, irmc and redfish, support automatic setting of the boot mode during deployment. This step is not required for them. Please check Drivers, Hardware Types and Hardware Interfaces for information on whether your driver requires manual UEFI configuration.

Legacy BIOS - Syslinux setup¶

In order to deploy instances with PXE on bare metal using Legacy BIOS boot mode, perform these additional steps on the ironic conductor node.

Install the syslinux package with the PXE boot images:

Ubuntu (16.04LTS and later):

sudo apt-get install syslinux-common pxelinux

RHEL7/CentOS7:

sudo yum install syslinux-tftpboot

Fedora:

sudo dnf install syslinux-tftpboot

SUSE:

sudo zypper install syslinux

Copy the PXE image to /tftpboot. The PXE image might be found at 1:

Ubuntu (16.04LTS and later):
```
sudo cp /usr/lib/PXELINUX/pxelinux.0 /tftpboot
```
RHEL7/CentOS7/SUSE:
```
sudo cp /usr/share/syslinux/pxelinux.0 /tftpboot
```

If whole disk images need to be deployed via PXE-netboot, copy the chain.c32 image to /tftpboot to support it:

Ubuntu (16.04LTS and later):

sudo cp /usr/lib/syslinux/modules/bios/chain.c32 /tftpboot

Fedora:

sudo cp /boot/extlinux/chain.c32 /tftpboot

RHEL7/CentOS7/SUSE:

sudo cp /usr/share/syslinux/chain.c32 /tftpboot/

If the version of syslinux is greater than 4 we also need to make sure that we copy the library modules into the /tftpboot directory 2 1. For example, for Ubuntu run:
```
sudo cp /usr/lib/syslinux/modules/*/ldlinux.* /tftpboot
```
Update the bare metal node with boot_mode:bios capability in node’s properties field. See Boot mode support for details.
Make sure that bare metal node is configured to boot in Legacy BIOS boot mode and boot device is set to network/pxe.

1(1,2): On Fedora/RHEL the syslinux-tftpboot package already installs the library modules and PXE image at /tftpboot. If the TFTP server is configured to listen to a different directory you should copy the contents of /tftpboot to the configured directory
2: http://www.syslinux.org/wiki/index.php/Library_modules

iPXE setup¶

If you will be using iPXE to boot instead of PXE, iPXE needs to be set up on the Bare Metal service node(s) where ironic-conductor is running.

Make sure these directories exist and can be written to by the user the ironic-conductor is running as. For example:

sudo mkdir -p /tftpboot
sudo mkdir -p /httpboot
sudo chown -R ironic /tftpboot
sudo chown -R ironic /httpboot

Create a map file in the tftp boot directory (/tftpboot):

echo 'r ^([^/]) /tftpboot/\1' > /tftpboot/map-file
echo 'r ^(/tftpboot/) /tftpboot/\2' >> /tftpboot/map-file

Set up TFTP and HTTP servers.

These servers should be running and configured to use the local /tftpboot and /httpboot directories respectively, as their root directories. (Setting up these servers is outside the scope of this install guide.)

These root directories need to be mounted locally to the ironic-conductor services, so that the services can access them.

The Bare Metal service’s configuration file (/etc/ironic/ironic.conf) should be edited accordingly to specify the TFTP and HTTP root directories and server addresses. For example:
```
[pxe]

# Ironic compute node's tftp root path. (string value)
tftp_root=/tftpboot

# IP address of Ironic compute node's tftp server. (string
# value)
tftp_server=192.168.0.2

[deploy]
# Ironic compute node's http root path. (string value)
http_root=/httpboot

# Ironic compute node's HTTP server URL. Example:
# http://192.1.2.3:8080 (string value)
http_url=http://192.168.0.2:8080
```
Install the iPXE package with the boot images:

Ubuntu:
```
apt-get install ipxe
```
RHEL7/CentOS7:
```
yum install ipxe-bootimgs
```
Fedora:
```
dnf install ipxe-bootimgs
```
Note

SUSE does not provide a package containing iPXE boot images. If you are using SUSE or if the packaged version of the iPXE boot image doesn’t work, you can download a prebuilt one from http://boot.ipxe.org or build one image from source, see http://ipxe.org/download for more information.

Copy the iPXE boot image (undionly.kpxe for BIOS and ipxe.efi for UEFI) to /tftpboot. The binary might be found at:

Ubuntu:

cp /usr/lib/ipxe/{undionly.kpxe,ipxe.efi,snponly.efi} /tftpboot

Fedora/RHEL7/CentOS7:

cp /usr/share/ipxe/{undionly.kpxe,ipxe.efi,snponly.efi} /tftpboot

Enable/Configure iPXE overrides in the Bare Metal Service’s configuration file if required (/etc/ironic/ironic.conf):
```
[pxe]

# Enable iPXE boot. (boolean value)
ipxe_enabled=True

# Neutron bootfile DHCP parameter. (string value)
ipxe_bootfile_name=undionly.kpxe

# Bootfile DHCP parameter for UEFI boot mode. (string value)
uefi_ipxe_bootfile_name=ipxe.efi

# Template file for PXE configuration. (string value)
ipxe_config_template=$pybasedir/drivers/modules/ipxe_config.template
```
Note

Most UEFI systems have integrated networking which means the [pxe]uefi_ipxe_bootfile_name setting should be set to snponly.efi.

Note

Setting the iPXE parameters noted in the code block above to no value, in other words setting a line to something like ipxe_bootfile_name= will result in ironic falling back to the default values of the non-iPXE PXE settings. This is for backwards compatability.
Ensure iPXE is the default PXE, if applicable.

In earlier versions of ironic, a [pxe]ipxe_enabled setting allowing operators to declare the behavior of the conductor to exclusively operate as if only iPXE was to be used. As time moved on, iPXE functionality was moved to it’s own ipxe boot interface.

If you want to emulate that same hehavior, set the following in the configuration file (/etc/ironic/ironic.conf):
```
[DEFAULT]
default_boot_interface=ipxe
enabled_boot_interfaces=ipxe,pxe
```
Note

The [DEFAULT]enabled_boot_interfaces setting may be exclusively set to ipxe, however ironic has multiple interfaces available depending on the hardware types available for use.
It is possible to configure the Bare Metal service in such a way that nodes will boot into the deploy image directly from Object Storage. Doing this avoids having to cache the images on the ironic-conductor host and serving them via the ironic-conductor’s HTTP server. This can be done if:
1. the Image Service is used for image storage;
2. the images in the Image Service are internally stored in Object Storage;
3. the Object Storage supports generating temporary URLs for accessing objects stored in it. Both the OpenStack Swift and RADOS Gateway provide support for this.
  - See Ceph Object Gateway support on how to configure the Bare Metal Service with RADOS Gateway as the Object Storage.
Configure this by setting the [pxe]/ipxe_use_swift configuration option to True as follows:
```
[pxe]

# Download deploy images directly from swift using temporary
# URLs. If set to false (default), images are downloaded to
# the ironic-conductor node and served over its local HTTP
# server. Applicable only when 'ipxe_enabled' option is set to
# true. (boolean value)
ipxe_use_swift=True
```
Although the HTTP server still has to be deployed and configured (as it will serve iPXE boot script and boot configuration files for nodes), such configuration will shift some load from ironic-conductor hosts to the Object Storage service which can be scaled horizontally.

Note that when SSL is enabled on the Object Storage service you have to ensure that iPXE firmware on the nodes can indeed boot from generated temporary URLs that use HTTPS protocol.

Restart the ironic-conductor process:

Fedora/RHEL7/CentOS7/SUSE:

sudo systemctl restart openstack-ironic-conductor

Ubuntu:

sudo service ironic-conductor restart

PXE multi-architecture setup¶

It is possible to deploy servers of different architecture by one conductor. To use this feature, architecture-specific boot and template files must be configured using the configuration options [pxe]pxe_bootfile_name_by_arch and [pxe]pxe_config_template_by_arch respectively, in the Bare Metal service’s configuration file (/etc/ironic/ironic.conf).

These two options are dictionary values; the key is the architecture and the value is the boot (or config template) file. A node’s cpu_arch property is used as the key to get the appropriate boot file and template file. If the node’s cpu_arch is not in the dictionary, the configuration options (in [pxe] group) pxe_bootfile_name, pxe_config_template, uefi_pxe_bootfile_name and uefi_pxe_config_template will be used instead.

In the following example, since ‘x86’ and ‘x86_64’ keys are not in the pxe_bootfile_name_by_arch or pxe_config_template_by_arch options, x86 and x86_64 nodes will be deployed by ‘pxelinux.0’ or ‘bootx64.efi’, depending on the node’s boot_mode capability (‘bios’ or ‘uefi’). However, aarch64 nodes will be deployed by ‘grubaa64.efi’, and ppc64 nodes by ‘bootppc64’:

[pxe]

# Bootfile DHCP parameter. (string value)
pxe_bootfile_name=pxelinux.0

# On ironic-conductor node, template file for PXE
# configuration. (string value)
pxe_config_template = $pybasedir/drivers/modules/pxe_config.template

# Bootfile DHCP parameter for UEFI boot mode. (string value)
uefi_pxe_bootfile_name=bootx64.efi

# On ironic-conductor node, template file for PXE
# configuration for UEFI boot loader. (string value)
uefi_pxe_config_template=$pybasedir/drivers/modules/pxe_grub_config.template

# Bootfile DHCP parameter per node architecture. (dict value)
pxe_bootfile_name_by_arch=aarch64:grubaa64.efi,ppc64:bootppc64

# On ironic-conductor node, template file for PXE
# configuration per node architecture. For example:
# aarch64:/opt/share/grubaa64_pxe_config.template (dict value)
pxe_config_template_by_arch=aarch64:pxe_grubaa64_config.template,ppc64:pxe_ppc64_config.template

Note

The grub implementation may vary on different architecture, you may need to tweak the pxe config template for a specific arch. For example, grubaa64.efi shipped with CentoOS7 does not support linuxefi and initrdefi commands, you’ll need to switch to use linux and initrd command instead.

Note

A [pxe]ipxe_bootfile_name_by_arch setting is available for multi-arch iPXE based deployment, and defaults to the same behavior as the comperable [pxe]pxe_bootfile_by_arch setting for standard PXE.

PXE timeouts tuning¶

Because of its reliance on UDP-based protocols (DHCP and TFTP), PXE is particularly vulnerable to random failures during the booting stage. If the deployment ramdisk never calls back to the bare metal conductor, the build will be aborted, and the node will be moved to the deploy failed state, after the deploy callback timeout. This timeout can be changed via the conductor.deploy_callback_timeout configuration option.

Starting with the Train release, the Bare Metal service can retry PXE boot if it takes too long. The timeout is defined via pxe.boot_retry_timeout and must be smaller than the deploy_callback_timeout, otherwise it will have no effect.

For example, the following configuration sets the overall timeout to 60 minutes, allowing two retries after 20 minutes:

[conductor]
deploy_callback_timeout = 3600

[pxe]
boot_retry_timeout = 1200