This page is specific to Ubuntu versions 8.04, 8.10, 9.04, 9.10, 10.04, 10.10

If you find this information applicable to additional versions/releases, please edit this page and modify this header to reflect that. Please also include any necessary modifications for this information to apply to the additional versions.

The Trivial File Transfer Protocol (TFTP) is a protocol used by LTSP clients to download some necessary files (pxelinux.0, vmlinuz and initrd.img) very early in their boot process, and lts.conf a bit later. tftpd-hpa is used by default as the tftp daemon in Ubuntu. Here are some steps that may help in troubleshooting tftpd-related problems.

Is tftpd-hpa running?

tftpd listens on port 69. To check if tftpd-hpa is running, on Lucid, run:

$ sudo status tftpd-hpa
tftpd-hpa start/running, process 1760

On Ubuntu versions prior to Lucid, run:

$ ss -anup | grep :69
UNCONN  0  0  *:69  *:*  users(("in.tftpd",...))

tftpd-hpa isn't running

If it isn't running, check your configuration files:

On Lucid

On Lucid, tftpd-hpa is started as a standalone daemon from upstart. So,

$ grep tftp /etc/inetd.conf

should return nothing. There were some bug reports about /etc/default/tftpd-hpa not being correct though, usually on upgrades. Verify that it contains the following:

# /etc/default/tftpd-hpa


Then, start tftpd-hpa by running:

sudo start tftpd-hpa

On Karmic or previous versions

On previous Ubuntu versions tftpd-hpa was started from inetd:

$ grep tftp /etc/inetd.conf
tftp           dgram   udp     wait    root  /usr/sbin/in.tftpd /usr/sbin/in.tftpd -s /var/lib/tftpboot

If your output doesn't match the line above, modify inetd.conf appropriately. Also check that /etc/default/tftpd-hpa is as follows:

#Defaults for tftpd-hpa
OPTIONS="-l -s /var/lib/tftpboot"

Finally, restart openbsd-inetd so that tftpd-hpa is reloaded:

sudo invoke-rc.d openbsd-inetd restart

Verify that the tftp files are there

To verify that the files needed for PXE booting the clients are actually there, run the following as a normal user, and check both the files and their permissions:

$ ls -l /var/lib/tftpboot/ltsp/i386
-rw-r--r-- 1 root   root     651618 2010-08-19 09:10 abi-2.6.32-24-generic
-rw-r--r-- 1 root   root     115905 2010-08-19 09:10 config-2.6.32-24-generic
lrwxrwxrwx 1 root   root         28 2010-08-23 22:39 initrd.img -> initrd.img-2.6.32-24-generic
-rw-r--r-- 1 root   root    8982381 2010-08-23 22:39 initrd.img-2.6.32-24-generic
-rw-r--r-- 1 root   root       7686 2010-08-26 01:47 lts.conf
lrwxrwxrwx 1 root   root         25 2010-08-23 22:39 nbi.img -> nbi.img-2.6.32-24-generic
-r--r--r-- 1 root   root   13010842 2010-08-23 09:15 nbi.img-2.6.32-24-generic
-rw-r--r-- 1 root   root      14776 2010-08-23 09:15 pxelinux.0
drwxr-xr-x 2 root   root       4096 2010-08-23 09:15 pxelinux.cfg
-rw-r--r-- 1 root   root    1689036 2010-08-19 09:10
-rw-r--r-- 1 root   root       1196 2010-08-19 09:12 vmcoreinfo-2.6.32-24-generic
lrwxrwxrwx 1 root   root         25 2010-08-23 22:39 vmlinuz -> vmlinuz-2.6.32-24-generic
-rw-r--r-- 1 root   root    4034976 2010-08-19 09:10 vmlinuz-2.6.32-24-generic

If the directory is missing, it's possible that you didn't run ltsp-build-client yet. If you did run ltsp-build-client, then you may have experienced a bug where the files go to /srv/tftp instead. If so, move them to /var/lib/tftpboot.

Use an external tftp client

If your clients won't boot after the steps above, and you're suspecting that something is still wrong with your server (e.g. some firewall), then you can try installing the tftp client, either on the LTSP server itself, or better yet, on a separate workstation:

sudo apt-get install tftp-hpa

Then, try the following commands to make sure that tftpd-hpa is working as expected:

$ cd /tmp
$ tftp -v -m binary -c get /ltsp/i386/pxelinux.0
mode set to octet
Connected to (, port 69
getting from to pxelinux.0 [octet]
Received 14776 bytes in 0.0 seconds [2672575 bit/s]

...where in the example stands for the LTSP server IP.

Check /etc/ltsp/dhcpd.conf

If you can download pxelinux.0 from a tftp client but your clients won't boot, it's possible that they're trying to download the wrong file, or that they're trying to contact the wrong server. The dhcp3-server configuration file, /etc/ltsp/dhcpd.conf, is used to tell the clients where to find pxelinux.0, using the filename directive, and which server to contact, using the next-server directive (not needed when the tftp daemon is running on the LTSP server). Verify that it looks like the following example:

# Default LTSP dhcpd.conf config file.


subnet netmask {
    option domain-name "";
    option domain-name-servers;
    option broadcast-address;
    option routers;
#    next-server;
#    get-lease-hostnames true;
    option subnet-mask;
    option root-path "/opt/ltsp/i386";
    if substring( option vendor-class-identifier, 0, 9 ) = "PXEClient" {
        filename "/ltsp/i386/pxelinux.0";
    } else {
        filename "/ltsp/i386/nbi.img";

If you modify that file, you'll have to restart dhcp3-server by running:

sudo invoke-rc.d dhcp3-server restart

Use gPXE to check the client side

If you followed all the previous paragraphs and your clients still won't boot, it's possible that somehow they receive wrong DHCP options, for example in the case when there's a rogue DHCP server on your network. gPXE (former Etherboot) is an open source network bootloader, which can be used to check that the client actually receives the correct DHCP options. Download a bootable CD, floppy, or USB image from, boot with it, press Ctrl+B to enter the gPXE command prompt, and run the following commands:

dhcp net0

Verify that next-server corresponds to the IP of your LTSP server, and that the filename option is /ltsp/i386/pxelinux.0.

See Also

UbuntuLTSP/Troubleshooting/TFTP (last edited 2011-05-12 13:09:54 by jengelh)