[Ltsp-discuss] TFTP: Open Timeout error on client (or Transfer timed out error on server)

[John H. <lt...@pr...>]

I had a thread named "LTSP-PNP on Lubuntu: Chromium 
ERR_NAME_RESOLUTION_FAILED," but am starting a new thread to accurately 
reflect the problem I'm now wrestling with.

I'm trying to troubleshoot an LTSP (the new LTSP-PNP) client boot 
problem under Quantal.  I installed with a single NIC per 
https://help.ubuntu.com/community/UbuntuLTSP/ltsp-pnp

The problem is that the LTSP client, after successfully getting DHCP 
assignments, fails to download the pxelinux boot image.  It reports 
"PXE-E32: TFTP open timeout."

To be more specific on the DHCP assignments, it identifies my hardware 
router as the DHCP server and the default gateway. It identifies the 
LTSP server as proxy and boot server.

I can also run this on the server itself to get a similar failure:
$ cd /tmp
$ tftp 192.168.1.102 -v -m binary -c get /ltsp/i386/pxelinux.0
mode set to octet
Connected to 192.168.1.102 (192.168.1.102), port 69
getting from 192.168.1.102:/var/lib/tftpboot/ltsp/i386/pxelinux.0 to 
pxelinux.0 [octet]
Transfer timed out.

A CRITICAL NOTE: This is using the default network-manager to configure 
the network interface (using the default DHCP configuration, and the 
connection is "Available to all users").  Apparently network-manager 
also runs or works with dnsmasq, which provide DHCP and TFTP servers.

When I had TFTP and DHCP errors booting the client under LTSP5 and 
Precise, I learned that the usual work-around was to configure the 
network interface(s) via /etc/network/interfaces. I think this solved 
some sort of a timing problem with the relevant services during bootup.

But that approach is apparently deprecated under Quantal and LTSP-PNP.  
In fact, I can use that approach to get the client to boot successfully, 
but it introduces a new problem on server and client: DNS resolution 
fails.  I understand that this happens because a non-default 
/etc/network/interfaces causes ifupdown to configure network interfaces 
instead of network-manager, but now network-manager is being relied upon 
to provide DNS resolutionwith dnsmasq.

I can fix the DNS resolution problem by creating 
/etc/resolvconf/resolv.conf.d/tail with contents:
nameserver (my nameserver 1)
nameserver (my nameserver 2)

-----------------------

But instead of patching up the old approach, I'd like to get the new 
approach working right.

Looking for others who have dealt with the same problem, I have not 
found much, but there was this 2010 thread: 
http://ubuntuforums.org/showthread.php?t=1503710

One of the posters (#6) says that when he disabled NAT, TFTP started 
working.  I don't know what that means for me in my setup.  But it did 
get me to thinking about my little network running from my 
consumer-class hardware router.  Is dnsmasq in conflict with a service 
being provided by the router?  Is my router's firewall blocking FTP 
communication between LTSP client and server?

If those are fruitless questions, then I would wonder why TFTP works 
when I use /etc/network/interfaces and ifupdown to configure the network 
interface, and it fails when network-manager governs instead.

By the way, this installation has seen very little modification. I 
installed Quantal on a newly-formatted hard drive, allowing it to use 
its default partitioning.  I installed LTSP-PNP.  I set up a scanner via 
already-installed SANE.  Also apcupsd for the sake of use with a UPS.  I 
installed HPLIP and an HP Laserjet printer.

-----------------------------

My (as-installed default) ltsp-server-dnsmasq.confin case that is of 
interest:

# Configures dnsmasq for PXE client booting.
# All the files in /etc/dnsmasq.d/ override the main dnsmasq 
configuration in
# /etc/dnsmasq.conf.
# You may modify this file to suit your needs, or create new ones in 
dnsmasq.d/.

# Log lots of extra information about DHCP transactions.
#log-dhcp

# IP ranges to hand out.
dhcp-range=192.168.67.20,192.168.67.250,8h

# If another DHCP server is present on the network, you may use a proxy 
range
# instead. This makes dnsmasq provide boot information but not IP leases.
# (needs dnsmasq 2.48+)
dhcp-range=192.168.1.0,proxy

# The rootpath option is used by both NFS and NBD.
dhcp-option=17,/opt/ltsp/i386

# Define common netboot types.
dhcp-vendorclass=etherboot,Etherboot
dhcp-vendorclass=pxe,PXEClient
dhcp-vendorclass=ltsp,"Linux ipconfig"

# Set the boot filename depending on the client vendor identifier.
# The boot filename is relative to tftp-root.
dhcp-boot=net:pxe,/ltsp/i386/pxelinux.0
dhcp-boot=net:etherboot,/ltsp/i386/nbi.img
dhcp-boot=net:ltsp,/ltsp/i386/lts.conf

# Kill multicast.
dhcp-option=vendor:pxe,6,2b

# Disable re-use of the DHCP servername and filename fields as extra
# option space. That's to avoid confusing some old or broken DHCP clients.
dhcp-no-override

# We don't want a PXE menu since we're using a graphical PXELinux menu.
#pxe-prompt="Press F8 for boot menu", 3

# The known types are x86PC, PC98, IA64_EFI, Alpha, Arc_x86,
# Intel_Lean_Client, IA32_EFI, BC_EFI, Xscale_EFI and X86-64_EFI
pxe-service=X86PC, "Boot from network", /ltsp/i386/pxelinux

# A boot service type of 0 is special, and will abort the
# net boot procedure and continue booting from local media.
#pxe-service=X86PC, "Boot from local hard disk", 0

# Comment the following to disable the TFTP server functionality of dnsmasq.
enable-tftp

# The TFTP directory. Sometimes /srv/tftp is used instead.
tftp-root=/var/lib/tftpboot/

# Disable the DNS server functionality of dnsmasq by setting port=0
port=0

# Don't listen on lo, to prevent conflicts with Ubuntu's local resolver 
hack (LP: #959037).
#except-interface=lo
#bind-interfaces