Copiado da pagina https://wiki.debian.org/PXEBootInstall

Preconditions¶

The computer you want to install to will be called the Client.

The computer you install from will be called the Server. We assume that the Server is running Debian.

To be specific, we assume that the Client and the Server are part of a LAN with the following IP addresses:

192.168.0.1 router (i.e. LAN default gateway) and DNS recursive server
192.168.0.2 the Server (will host a DHCP and TFTP server)
192.168.0.x the Client
You will find out the value of x later.

Note that many routers also provide a DHCP server: you will have to turn it off, since only one DHCP server can run in a given LAN. Unless you may configure your router's DHCP sever to comply with the ISC DHCP server configuration below, but this is outside of the scope of this document.

It is also possible that the router and the server are the same machine, i.e. that your Debian server is the default gateway for this LAN. This will work fine.

The following instructions have been tested with Debian 6.0 (squeeze) in January 2012.

Activate PXE boot¶

Setup the BIOS boot menu of the Client to boot from the network.

Reboot. This should produce an output that contains the Client's MAC address. Then, it will fail with

PXE-E53: no boot filename received.

Note the MAC address, you will need it in a minute.

On many servers, it is also possible to temporary switch to PXE boot without permanently changing the BIOS settings. There will be some kind of key stroke to hit during BIOS POST. On Dell servers, F12 will do the trick (or Esc then @ from a serial or IPMI console).

Set up DHCP server¶

On the Server, we need to set up a DHCP server.

Current best practice seems to be to use the package isc-dhcp-server, which provides a daemon dhcpd.

It's configuration file is /etc/dhcp/dhcpd.conf. Modify this file so that it contains about the following; adapt IP and MAC addresses to your local needs:

default-lease-time 600;
max-lease-time 7200;

allow booting;

# in this example, we serve DHCP requests from 192.168.0.(3 to 253)
# and we have a router at 192.168.0.1

subnet 192.168.0.0 netmask 255.255.255.0 {
  range 192.168.0.3 192.168.0.253;
  option broadcast-address 192.168.0.255;
  option routers 192.168.0.1;             # our router
  option domain-name-servers 192.168.0.1; # our router, again
  filename "pxelinux.0"; # (this we will provide later)
}

group {
  next-server 192.168.0.2;                # our Server
  host tftpclient {
    filename "pxelinux.0"; # (this we will provide later)
  }
}

After each modification of the above, restart the DHCP server with

 # /etc/init.d/isc-dhcp-server restart

Check that it is actually running:

  # pgrep -lf dhcpd
  32277 /usr/sbin/dhcpd -q

Reboot the Client. On success, it will output the IP addresses of the Server ("DHCP"), of the router ("Gateway") and of itself (192.168.0.x). Then it will hang with a TFTP request, and finally write the error message:

  PXE-E32: TFTP open timeout

For diagnostic purposes, look up /var/log/daemon.log, you should see:

Jun  3 09:53:46 server dhcpd: DHCPDISCOVER from 40:01:1c:47:44:1e via eth0
Jun  3 09:53:47 server dhcpd: DHCPOFFER on 192.168.0.3 to 40:01:1c:47:44:1e via eth0
Jun  3 09:53:51 server dhcpd: DHCPREQUEST for 192.168.0.3 (192.168.0.2) from 40:01:1c:47:44:1e via eth0
Jun  3 09:53:51 server dhcpd: DHCPACK on 192.168.0.3 to 40:01:1c:47:44:1e via eth0

If nothing appears in the log, check the network links between the Server and the Client. Note that some switches may impose severe limitations on DHCP traffic; for Cisco ones, use 'portfast' if possible (see http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a00800b1500.shtml).

Set up TFTP server¶

Next, we need to set up a TFTP server on the Server.

Again, there are several packages that provide TFTP (trivial FTP, unsafe, to be used in LAN's only). It seems best practice is using the package tftpd-hpa. On installation, a few question are asked. The response to these questions goes into a configuration file, /etc/default/tftpd-hpa. There should be no need to modify the following default contents:

  TFTP_USERNAME="tftp" 
  TFTP_DIRECTORY="/srv/tftp" 
  TFTP_ADDRESS="0.0.0.0:69" 
  TFTP_OPTIONS="--secure" 

Ignore older Web sites that instruct you to insert something like 'RUN_DAEMON="yes"'.

After each modification of the above configuration file, restart the TFTP server with

  # /etc/init.d/tftpd-hpa restart

Initially, this will fail with a message like

  Restarting HPA's tftpd: in.tftpd/srv/tftp missing, aborting.

Therefore, as root, create the directory /srv/tftp. Restart the TFTP daemon. Check that it is actually running:

  # pgrep -lf tftpd
  12555 /usr/sbin/in.tftpd

It is useful to test your TFTP server with a TFTP client, you may simply use the tftp-hpa package for this purpose:

  # cd /tmp
  # uname -a >/srv/tftp/test
  # tftp 192.168.0.2
  tftp> get test
  tftp> quit
  # diff test /srv/tftp/test
  (nothing, they are identical)

Reboot the Client. You should see error messages starting with

  PXE-T01: File not found

which is quite correct since we did not yet provide any files.

Provide the boot image¶

Download netboot/netboot.tar.gz from a Debian mirror (see http://www.debian.org/distrib/netinst#netboot).

Optional: To verify the digitial signature, type these commands:

# wget http://"$YOURMIRROR"/debian/dists/wheezy/main/installer-"$ARCH"/current/images/netboot/netboot.tar.gz
# wget http://"$YOURMIRROR"/debian/dists/wheezy/main/installer-"$ARCH"/current/images/SHA256SUMS
# wget http://"$YOURMIRROR"/debian/dists/wheezy/Release
# wget http://"$YOURMIRROR"/debian/dists/wheezy/Release.gpg

# cat SHA256SUMS | grep -F netboot/netboot.tar.gz
ac278b204f768784824a108e7cf3ae8807f9969adcb4598effeff2b92055bb52  ./netboot/netboot.tar.gz
# sha256sum netboot.tar.gz
ac278b204f768784824a108e7cf3ae8807f9969adcb4598effeff2b92055bb52  netboot.tar.gz
(match!)

# sha256sum SHA256SUMS
4856ecb5015b93d7dd02249c91d03bd88890d44bd25d8a2d2a400bab63f9d7de  SHA256SUMS
# cat Release | grep -A 100000 '^SHA256' | grep -F installer-"$ARCH"/current/images/SHA256SUMS
4856ecb5015b93d7dd02249c91d03bd88890d44bd25d8a2d2a400bab63f9d7de    14289 main/installer-"$ARCH"/current/images/SHA256SUMS
(match!)

# gpg --verify Release.gpg Release
gpg: WARNING: multiple signatures detected.  Only the first will be checked.
gpg: Signature made Sat 15 Jun 2013 05:55:56 AM CDT using RSA key ID 473041FA
gpg: Good signature from "Debian Archive Automatic Signing Key (6.0/squeeze) <ftpmaster@debian.org>" 

Unpack netboot.tar.gz to /srv/tftp, which should now contain

  debian-installer/
  pxelinux.0@
  pxelinux.cfg@
  version.info

It may be necessary to chmod -R a+r * to make all files in this directory readable for the TFTP daemon.

Restart the TFTP daemon, then reboot the Client. You should get to a Debian install screen.

If you lookup into /var/log/daemon.log, you will see what has been downloaded from the TFTP server by the PXE bootloader, and then by SYSLINUX:

Jun  3 09:53:51 server tftpd.in[32698]: Serving pxelinux.0 to 192.168.0.3:2070
Jun  3 09:53:51 server tftpd.in[32698]: Serving pxelinux.0 to 192.168.0.3:2071
Jun  3 09:53:51 server tftpd.in[32698]: Serving pxelinux.cfg/44454c4c-5600-1048-8051-c7c04f575831 to 192.168.0.3:57089
Jun  3 09:53:51 server tftpd.in[32698]: Serving pxelinux.cfg/40-01-b1-1c-47-44-1e to 192.168.0.3:57090
Jun  3 09:53:51 server tftpd.in[32698]: Serving pxelinux.cfg/default to 192.168.0.3:57090
Jun  3 09:53:51 server tftpd.in[32698]: Serving bootmenu.txt to 192.168.0.3:57095

The PXE loader (the firmware in the BIOS or the network controller) try to load into that order:

pxelinux.0 (or more exactly, what you told it to download in the 'filename' field of the DHCP response)
Then SYSLINUX/PXELINUX will try to search its configuration at different paths, from the most specific to the least:

pxelinux.cfg/GUID
pxelinux.cfg/MAC
pxelinug.cfg/default
And if the configuration menu depends on other configuration items, they are also downloaded. Debian will at least need the 'bootmenu.txt' file which is the main menu.

Another Way - use Dnsmasq¶

dnsmasq is a lightweight, easy to configure DNS forwarder and DHCP server with BOOTP/TFTP/PXE functionality. That is, you can replace isc-dhcp-server and tftpd-hpa with Dnsmasq.

Following is the /etc/dnsmasq.conf providing the same functionality as the way of isc-dhcpd-server and tftpd-hpa described above.

interface=eth1
domain=yourdomain.com
dhcp-range=192.168.0.3,192.168.0.253,255.255.255.0,1h
dhcp-boot=pxelinux.0,pxeserver,192.168.0.2
pxe-service=x86PC, "Install Linux", pxelinux
enable-tftp
tftp-root=/srv/tftp

Download the netboot.tar.gz and extract it in the /srv/tftp as previous description.