xref: /titanic_51/usr/src/man/man5/pxeboot.5 (revision 26c793cfccd2fcf61e733b496241b8baf667fe8b)
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25.Dd May 25, 2017
26.Dt PXEBOOT 5
27.Os
28.Sh NAME
29.Nm pxeboot
30.Nd Preboot Execution Environment (PXE) bootloader
31.Sh DESCRIPTION
32The
33.Nm
34bootloader is a modified version of the system third-stage bootstrap
35.Xr loader 5
36configured to run under Intel's Preboot Execution Environment (PXE) system.
37PXE is a form of smart boot ROM, built into Ethernet cards, and
38Ethernet-equipped motherboards.
39PXE supports DHCP configuration and provides low-level NIC access services.
40The
41.Nm
42bootloader retrieves the kernel, modules,
43and other files either via NFS over UDP or by TFTP,
44selectable through DHCP options.
45.Pp
46The
47.Nm
48binary is loaded just like any other boot file,
49by specifying it in the DHCP server's configuration file.
50Below is a sample configuration for the ISC DHCP v2 server:
51.Bd -literal -offset indent
52option domain-name "example.com";
53option routers 10.0.0.1;
54option subnet-mask 255.255.255.0;
55option broadcast-address 10.0.0.255;
56option domain-name-servers 10.0.0.1;
57server-name "DHCPserver";
58server-identifier 10.0.0.1;
59
60default-lease-time 120;
61max-lease-time 120;
62
63subnet 10.0.0.0 netmask 255.255.255.0 {
64       filename "pxeboot";
65       range 10.0.0.10 10.0.0.254;
66}
67
68.Ed
69.Pp
70.Nm
71recognizes
72.Va next-server
73and
74.Va option root-path
75directives as the server and path to NFS mount for file requests,
76respectively, or the server to make TFTP requests to.
77Note that
78.Nm
79expects to fetch
80.Pa /boot/loader.rc
81from the specified server before loading any other files.
82.Pp
83.Nm
84defaults to a conservative 1024 byte NFS data packet size.
85This may be changed by setting the
86.Va nfs.read_size
87variable in
88.Pa /boot/loader.conf .
89Valid values range from 1024 to 4096 bytes.
90.Pp
91.Nm
92chooses NFS or TFTP based on the value of
93.Va root-path
94variable provided by the DHCP server.
95.Nm
96defaults to use NFS if the
97.Va root-path
98variable is in the
99.Qq Pa ip-address Ns :/ Ns Pa path
100form, otherwise TFTP is used.
101.Pp
102TFTP block size can be controlled by setting the
103.Va tftp.blksize
104variable in
105.Pa /boot/loader.conf .
106Valid values range from 8 to 9008 bytes.
107.Pp
108In all other respects,
109.Nm
110acts just like
111.Xr loader 5 .
112.Pp
113For further information on Intel's PXE specifications and Wired for
114Management (WfM) systems, see
115.Li http://www.intel.com/design/archives/wfm/ .
116.Sh SEE ALSO
117.Xr loader 5
118