Certain machines can't boot from linux PXE server, pxelinux.0 file not found

What:

PXE boot server on Raspberry PI, Lenovo ThinkCentre A70z client

Problem:

When I am trying to boot from the network I get:

PXE-T01: file not found
PXE-E3B-TFTP Error file not found
PXE-M0F exiting Intel boot agent

Solution:

All files on TFTP server are in correct locations, also DHCP provides good config, boot fails only on certain pc's.

Below solution will only work with tftp-hpa TFTP server.

Troubleshooting

Let's see what file is actually being called.

 vi /etc/default/tftpd-hpa

Set the verbose flag, which will send all messages to the syslog

TFTP_OPTIONS="--secure --ipv4 --verbose --verbosity 5"

Restart tftp server to apply changes.

/etc/init.d/tftpd-hpa restart

Confirm that daemon is running with verbose flag set.

ps aux | grep tftpd

Watch a log file.

tail -f /var/log/syslog

Try to boot from the network again.

In syslog you should see that client is looking for the below file.

pxelinux.0�

It has some weird character added at the end, hence it can't find the original file.

You can also sniff packets with tcpdump.

tcpdump -ni eth0 -v -T tftp 'udp'

Output:

pxelinux.0M-^?

Solution

Apparently some old PXE stacks have a bug. What's added to the file name is a hex value 0xFF, which encodes to ÿ.

1. From Ubuntu desktop ssh to TFTP server (if you haven't already).
2. In gnome-terminal change encoding, Terminal > Set Character Encoding > Add or Remove, select ISO-8859-1
3. Now if you try to boot your client again in log you should see encoded character.
4. Check if your tftp-hpa supports map file.

/usr/sbin/in.tftpd -V

5. If yes, then let's create one.
echo 'rg (.*)ÿ$ \1' > /etc/default/tftpd-hpa.map
6. Add map file to your configuration

vi /etc/default/tftpd-hpa

TFTP_OPTIONS="--secure --ipv4 --map-file /etc/default/tftpd-hpa.map"

 /etc/init.d/tftpd-hpa restart

7. Now client should boot fine.