pxeboot(8) - NetBSD Manual Pages

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PXEBOOT(8)            NetBSD/i386 System Manager's Manual           PXEBOOT(8)


NAME

     pxeboot -- network boot NetBSD/i386 through a PXE BIOS extension


DESCRIPTION

     pxeboot is a NetBSD boot program running on top of a PXE BIOS extension
     which is provided by the motherboard or a plug-in network adapter, in
     accordance with the Intel Preboot eXecution Environement (PXE) specifica-
     tion.

     Network booting a system through PXE is a two-stage process:

     1.   The PXE BIOS issues a DHCP request and fetches the NetBSD pxeboot
          program using TFTP.

     2.   The NetBSD pxeboot program takes control.  An interactive mode is
          entered if the user presses a key within five seconds.  After this
          time or after the user's boot command, another DHCP request is
          issued and the kernel is loaded as specified in the DHCP reply.  To
          read the kernel file, the NFS (version 2) or TFTP protocols can be
          used.

     The DHCP request issued by the NetBSD pxeboot program has the following
     special parameters:

     Bootfile name
           is set to the filename argument on the boot command line typed in
           by the user (can be empty), or to ``netbsd'' in the non-interactive
           case.

     DHCP Vendor class identifier tag
           is set to ``NetBSD:i386:libsa''.

     The DHCP server can use these fields to distinguish between the various
     originators of requests (first and second PXE stage, NetBSD kernel), and
     to control conditional behaviour depending on the user's command line
     input to the pxeboot program, e.g. to support alternative NetBSD instal-
     lations on one machine.

     In addition to the standard network interface configuration, the follow-
     ing fields in the DHCP reply are interpreted:

     Bootfile name
           specifies the protocol to be used, and the filename of the NetBSD
           kernel to be booted, separated by a colon.  Available protocols are
           ``nfs'' and ``tftp''.  The kernel filename part is interpreted rel-
           atively to the NFS root directory (see the Root path reply field
           below) or the TFTP server's root directory (which might be a subdi-
           rectory within the TFTP server's filesystem, depending on the
           implementation), respectively.  If the Bootfile name field replied
           by the DHCP server does not contain a colon, it is ignored, and the
           filename typed in at the pxeboot command line prompt (or the
           ``netbsd'' default, see the section about the Bootfile name field
           in the DHCP request above) is used.  If no protocol was specified,
           ``nfs'' is assumed.

     Swap server
           can be used to override the ``server IP address'' if NFS is used to
           access the kernel.  This matches the behaviour of the NetBSD kernel
           to access its root file system on NFS.  This way, different TFTP
           and NFS servers can be communicated to the DHCP client (it is
           actually a deficiency of the DHCP protocol to provide a ``root
           path'' field but no corresponding IP address).

     Root path
           is used as path to be mounted in the NFS case to access the kernel
           file, matching the NetBSD kernel's behaviour.

     The commands accepted in interactive mode are:

         boot [filename] [-adqsv]
               Boot NetBSD.  See boot in boot(8) for full details.

         help  Print an overview about commands and arguments.

         quit  Leave the pxeboot program.


EXAMPLES

     The first /etc/dhcpd.conf example shows a simple configuration which just
     loads a file ``netbsd'' from the client's NFS root directory, using the
     defaults for protocol and kernel filename.  Similar setups should be pos-
     sible with any BOOTP/DHCP server.

     host myhost {
         hardware ethernet 00:00:00:00:00:00;
         fixed-address myhost;
         option host-name "myhost";
         filename "pxeboot_ia32.bin";
         option swap-server mynfsserver;
         option root-path "/export/myhost";
     }

     The following /etc/dhcpd.conf entry shows how different system installa-
     tions can be booted depending on the user's input on the pxeboot command
     line.

     host myhost {
         hardware ethernet 00:00:00:00:00:00;
         fixed-address myhost;
         option host-name "myhost";
         if substring (option vendor-class-identifier, 0, 9) = "PXEClient" {
             filename "pxeboot_ia32.bin";
         } elsif filename = "tftp" {
             filename "tftp:netbsd.myhost";
         } else {
             option swap-server mynfsserver;
             option root-path "/export/myhost";
             if filename = "generic" {
                 filename "nfs:gennetbsd";
             } else {
                 filename "nfs:netbsd";
             }
         }
     }

     It is assumed that the TFTP server is the same as the DHCP server unless
     a next-server directive is specified somewhere else in dhcpd.conf, and
     that the NFS server for the root file system is mynfsserver.  The
     swap-server:root-path is only used in the NFS case and by the NetBSD ker-
     nel to mount the root file system.


SEE ALSO

     boot(8), dhcpd(8), diskless(8)

     Intel Corporation, Preboot Execution Environment (PXE) Specification,
     Version 2.1, September 20, 1999.


HISTORY

     The NetBSD/i386 pxeboot command first appeared in NetBSD 1.6.


BUGS

     If an error is encountered while reading the NetBSD kernel file or if its
     file format wasn't recognized, it is impossible to retry the operation
     because the PXE network stack is already removed from the system RAM.

NetBSD 3.1                     November 17, 2003                    NetBSD 3.1