Ubuntu PXE Install

From C4 Wiki
Jump to: navigation, search


[edit] Howto

Installing Ubuntu or Debian via PXE network boot is the way to go if you have no cd-r at hand, or if you have no cdrom drive on the machine to be installed.

[edit] Install services

You need the following packages:

  • tftpd-hpa
  • dhcp3-server
  • netkit-inetd
sudo apt-get install tftpd-hpa dhcp3-server openbsd-inetd

Note: On Gutsy (7.10) and Debian Etch netkit-inetd is a "virtual package". Either inetutils-inetd or openbsd-inetd must be chosen. On one system, openbsd-inetd is already installed - the default now?

[edit] Prepare your tftp server

Start your tftpd server via inetd after adding the following line in /etc/inetd.conf:

tftp           dgram   udp     wait    root  /usr/sbin/in.tftpd /usr/sbin/in.tftpd -s /var/lib/tftpboot
sudo update-inetd --enable BOOT

Don't forget to create the tftp directory /var/lib/tftpboot (if it hasn't already been created)

On Ubuntu 6.06 Server and Feisty Fawn 7.04 (or if /etc/inetd.conf doesn't exist) you might edit /etc/default/tftpd-hpa:

OPTIONS="-l -s /var/lib/tftpboot"

and start the daemon via the command

 sudo /etc/init.d/tftpd-hpa start

Verify that inetd is listening on the right port:

netstat -lu

should show

udp        0      0 *:tftp                  *:*      

(On one Gutsy system, inetutils-inetd insisted on listening on an ipv6 socket, and booting via tftp failed. Switching to openbsd-inetd solved the problem.)

[edit] Prepare your dhcp-server

On what network interfaces should the DHCP server (dhcpd) serve DHCP requests? Answer this question by editing the line in /etc/default/dhcp3-server file. Separate multiple interfaces with spaces, e.g. "eth0 eth1". Eg:

INTERFACES="eth1 eth2"

If you have a working dhcp server add the following lines to your group in /etc/dhcpd.conf file (or, from Etch and Feisty upward, the /etc/dhcp3/dhcpd.conf file), substituting IP and MAC address as needed. Beware not to forget the semicolons (";") at the end of lines.

host pxeinstall {
  # ie. "hardware ethernet 00:0A:E4:2E:A6:42;"
  hardware ethernet [MAC address of PXE client networkcard, without brackets];

  # this is the unused IP address we will assign temporarily to the PXE client

  # Not needed if the tftp server is on the same host as the DHCP server. ie. "next-server;".
  # edit : Well needed, otherwise he is looking for the host so, it doesn't work
  next-server [ip-address of the server serving tftp]; 

  # path of the bootloader file, relative to tftpd's root
  filename "pxelinux.0";

The "next-server" stanza tells the PXE boot client where to look for the boot image and associated data. It is required in newer editions of tftpd-hpa, if not on the same machine as the DHCP server.

Instead, if you do not need MAC-based configuration (e.g. you want to be able to boot any host), you can just add a filename stanza to a subnet configuration (verified on Intrepid):

subnet netmask {
  option routers;
  #substitute the DNS addresses of your own Internet Service Provider (ISP)
  option domain-name-servers primary.dns.from.isp, secondary.dns.from.isp;
  filename "pxelinux.0";

You need to assign the client an IP address in the same subnet as the address of the server running tftpd. For example, if your server's address is, you should assign your client an IP address that begins with 192.168.2.x, NOT 192.168.0.x . If your client doesn't recieve an IP-address, you might want to add authoritative; above the subnet declaration.

When you are done configuring your dhcp server, (re)start it:

/etc/init.d/dhcp3-server restart

And verify it runs (if not, you may have a problem in the dhcpd config file):

ps ax | grep dhcpd

[edit] Prepare netboot files

[edit] Get and install the files

All the files you need are on the install media, or you can get them from internet:

Download and put the netboot directory content at the root of the tftpd's served /var/lib/tftpboot/ directory:

cd /var/lib/tftpboot/
lftp -c "open http://archive.ubuntu.com/ubuntu/dists/lucid/main/installer-i386/current/images/netboot/; mirror"

# then untar the pxeboot.tar.gz (this step is NOT needed anymore, as of Feisty)
tar xfz pxeboot.tar.gz

Alternatively, if Ubuntu is in your cdrom drive:

mount /media/cdrom
cp -a /media/cdrom/install/netboot/* /var/lib/tftpboot/

[edit] pxe bootloader config

In the pxelinux.cfg/ directory, make a symlink named after the pxe boot client's mac address (without the colons), and pointing to the "default" config file:

# ie. if our client mac address is 00:0A:E4:2E:A6:42, we'll do:
ln -s /var/lib/tftpboot/pxelinux.cfg/default /var/lib/tftpboot/pxelinux.cfg/000AE42EA642

For very old distros versions, you may need to edit or patch pxelinux.cfg/default . This modification is NOT needed anymore (at least from Feisty or Etch and up).

--- default.org	2004-10-31 15:32:32.000000000 +0100
+++ default	2004-10-31 00:14:52.000000000 +0200
@@ -13,17 +13,11 @@
 F0 debian-installer/boot-screens/f10.txt
 label linux
-	kernel debian-installer/linux
-	append vga=normal initrd=debian-installer/initrd.gz ramdisk_size=11057 root=/dev/rd/0 devfs=mount,dall rw --
+	kernel vmlinuz
+	append vga=normal initrd=initrd.gz ramdisk_size=11057 root=/dev/rd/0 devfs=mount,dall rw --
 label expert
-	kernel debian-installer/linux
-	append DEBCONF_PRIORITY=low vga=normal initrd=debian-installer/initrd.gz ramdisk_size=11057 root=/dev/rd/0 devfs=mount,dall rw --
-label custom
-	kernel debian-installer/linux
-	append ubuntu/install-type=custom vga=normal initrd=debian-installer/initrd.gz ramdisk_size=11057 root=/dev/rd/0 devfs=mount,dall rw --
-label custom-expert
-	kernel debian-installer/linux
-	append ubuntu/install-type=custom DEBCONF_PRIORITY=low vga=normal initrd=debian-installer/initrd.gz ramdisk_size=11057 root=/dev/rd/0 devfs=mount,dall rw --
+	kernel vmlinuz
+	append DEBCONF_PRIORITY=low vga=normal initrd=initrd.gz ramdisk_size=11057 root=/dev/rd/0 devfs=mount,dall rw --
 prompt 1
 timeout 0

[edit] Directory layout

Should look like this, more or less (depending on the Ubuntu or Debian installer version used):


In more detail we need to provide:

  • a bootloader, which name (or path relative to tftpd's served directory, here /var/lib/tftpboot) is mentioned in the dhcpd.conf file (pxelinux.0)
  • a configuration file for the bootloader (default for all clients, or mac specific)
  • a kernel with an initrd file (vmlinuz,initrd.gz)
  • an image of the base system (mini.iso)

[edit] Start the PXE client

Just boot up the computer that will use DHCP and then PXE to get the images, if something isn't working you can use a sniffer on your install server to check, and look at log files for daemons misconfigurations.

tshark -R bootp
tshark port tftp
sudo tcpdump -s 1600 -neeevvvX 'proto (\udp or \tcp) and port (67 or 68 or 69)'
tail /var/log/daemon.log

If your network card doesn't have a PXE stack, you can try downloading a stub client from http://rom-o-matic.net/

[edit] Optional: setup an archive mirror

With the previous setup, Ubuntu or Debian will download install packages straight over the internet. If you prefer to run your network installs over a private network and use your own Ubuntu or Debian mirror you can do the following:

sudo apt-get install apt-mirror

Then write an /etc/apt/mirror.list configuration file, eg.:

Example for Ubuntu dapper:

set base_path      /var/spool/apt-mirror/
deb http://gb.archive.ubuntu.com/ubuntu/ dapper main restricted
deb http://gb.archive.ubuntu.com/ubuntu/ dapper main/debian-installer
deb http://gb.archive.ubuntu.com/ubuntu/ dapper main restricted/debian-installer

Example for Debian Etch:

set base_path      /var/spool/apt-mirror/
deb http://ftp.us.debian.org/debian etch main contrib non-free
deb http://security.debian.org/debian-security etch/updates main contrib non-free
deb http://ftp.us.debian.org/debian etch main/debian-installer


mkdir -p /var/spool/apt-mirror/{mirror,var,skel}

This will replicate the mirror to your chosen base path. You will need to create the soft links to the dists and pool directories yourself, eg.:

~$ ls -al /var/spool/apt-mirror/mirror/
total 24
drwxr-xr-x   5 root root   4096 May 18 12:46 .
drwxrwxrwx  11 root root   4096 May 18 12:27 ..
lrwxrwxrwx   1 root root   34 May 18 12:46 dists -> gb.archive.ubuntu.com/ubuntu/dists
drwxr-xr-x   3 root root   4096 May 18 12:46 gb.archive.ubuntu.com
lrwxrwxrwx   1 root root   33 May 18 12:46 pool -> gb.archive.ubuntu.com/ubuntu/pool
drwxr-xr-x   3 root root   4096 May 18 10:53 skel
drwxr-xr-x   2 root root   8192 May 18 13:27 var
  • Serve the /var/spool/apt-mirror/ directory out with apache
  • When you boot the ubuntu/debian network installer, point it at the IP address and the 'mirror' directory.

[edit] Links

Personal tools