PXE Boot Using DNSMasq

lukasbradley · 02-24-2014, 03:15 PM

I'm attempting to boot machines from a server (192.168.1.45) over a network using PXE boot and DNSMasq. My network presently utilizes a DHCP server on a VPN/Firewall, so I don't want to run a DHCP server on the server itself.

When I start the client computer, it seems to connect to the server, but doesn't proceed with a boot. The remote computer just hangs showing "Start PXE over IPv4".

The /var/log/messages on the server shows the following.

Code:

Feb 24 15:10:45 localhost dnsmasq[14487]: started, version 2.48 DNS disabled
Feb 24 15:10:45 localhost dnsmasq[14487]: compile time options: IPv6 GNU-getopt DBus no-I18N DHCP TFTP "--bind-interfaces with SO_BIN
DTODEVICE"
Feb 24 15:10:45 localhost dnsmasq-dhcp[14487]: DHCP, proxy on subnet 192.168.1.255
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 Available DHCP subnet: 192.168.1.255/255.255.255.0
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 Vendor class: PXEClient:Arch:00007:UNDI:003016
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 PXE(eth0) bc:5f:f4:97:be:ab proxy
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 tags: eth0
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 bootfile name: pxelinux.0
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 next server: 192.168.1.45
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 sent size:  1 option: 53:message-type  02
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 sent size:  4 option: 54:server-identifier  192.168.1.45
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 sent size:  9 option: 60:vendor-class  50:58:45:43:6c:69:65:6e:74
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 sent size: 17 option: 97:client-machine-id  00:00:02:00:03:00:04:00:05:00:0
6:00:07...
Feb 24 15:11:20 localhost dnsmasq-dhcp[14487]: 3423833039 sent size: 10 option: 43:vendor-encap  06:01:08:0a:04:00:50:58:45:ff
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 Available DHCP subnet: 192.168.1.255/255.255.255.0
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 Vendor class: PXEClient:Arch:00007:UNDI:003016
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 PXE(eth0) bc:5f:f4:97:be:ab proxy
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 tags: eth0
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 bootfile name: pxelinux.0
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 next server: 192.168.1.45
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 sent size:  1 option: 53:message-type  02
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 sent size:  4 option: 54:server-identifier  192.168.1.45
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 sent size:  9 option: 60:vendor-class  50:58:45:43:6c:69:65:6e:74
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 sent size: 17 option: 97:client-machine-id  00:00:02:00:03:00:04:00:05:00:0
6:00:07...
Feb 24 15:11:24 localhost dnsmasq-dhcp[14487]: 3423833039 sent size: 10 option: 43:vendor-encap  06:01:08:0a:04:00:50:58:45:ff

The DNSMasq config is the following:

Code:

#set port to 0 so that dnsmasq knows its not being used as a dns server
port=0
log-dhcp
dhcp-range=192.168.1.255,proxy
#dhcp-boot=http://192.168.1.45/
enable-tftp
tftp-root=/var/lib/tftpboot
dhcp-boot=pxelinux.0,fileserver,192.168.1.45

The /var/lib/tftpboot directory:

Code:

drwxrwxr-x   3 root root     4096 Feb  4 10:35 .
drwxr-xr-x. 37 root root     4096 Feb 24 11:10 ..
-rw-r--r--   1 root root       97 Feb 24 15:02 boot.txt
drwxrwxr-x   3 root root     4096 Feb  4 10:35 debian-installer
-rw-r--r--   1 root root 24117248 Feb  4 10:35 mini.iso
-rw-r--r--   1 root root 13703974 Feb  4 10:35 netboot.tar.gz
lrwxrwxrwx   1 root root       33 Feb 24 15:07 pxelinux.0 -> debian-installer/amd64/pxelinux.0
lrwxrwxrwx   1 root root       35 Feb 24 15:07 pxelinux.cfg -> debian-installer/amd64/pxelinux.cfg
-rw-rw-r--   1 root root       64 Feb  4 10:35 version.info

My pxelinux.cfg configuration looks as follows:

Code:

# D-I config version 2.0
include debian-installer/amd64/boot-screens/menu.cfg
default debian-installer/amd64/boot-screens/vesamenu.c32
prompt 1
timeout 0

Any comments, suggestions, or insight appreciated.

boethius · 02-25-2014, 07:43 PM

dnsmasq can behave as a proxyDHCP server which sounds like what you want. You can continue to use your existing DHCP server and either have dnsmasq on the same network as the devices you're trying to PXE boot or you can DHCP relay to a dnsmasq server (i.e., ip helper in the Cisco world). Here is an example of a functional dnsmasq server setup to be a proxyDHCP server:

port=0
log-dhcp
dhcp-match=ipxe,175
dhcp-option=175,8:1:1
dhcp-boot=net:ipxe,http://mybootserver.domain.com/boot/ipxeboot/\${net0/mac}
dhcp-boot=tag:!Iipxe,ipxe.0
enable-tftp
tftp-root=/tftpboot
dhcp-range=192.168.0.0,proxy,255.255.0.0
dhcp-range=10.0.0.0,proxy,255.0.0.0
dhcp-range=172.16.0.0,proxy,255.255.0.0
pxe-service=net:#ipxe,x86PC,"Auto OS Deployment",ipxe-native

Dnsmasq's example configuration file details what each of these configuration options means. Note the example like this "dhcp-range=10.0.0.0,proxy,255.0.0.0" doesn't actually supplant or conflict with an existing DHCP server but merely facilitates proxyDHCP on that generic non-routable private network.

I'm showing my strong preference for iPXE here (ipxe.0 and ipxe-native.0, which I am compiling from the iPXE source) but you could just as easily use pxelinux for your network bootstrap.

Anyway, this works quite well in my experience and shows how useful proxyDHCP can be to be facilitate PXE booting without changing an existing DHCP environment (or, as is often the case, not even being able to change the existing DHCP environment).

Try it out and let me know if it works.