bootpd.8   [plain text]

.\" Copyright (c) 1999, 2005-2007 Apple Inc. All rights reserved.
.\" This file contains Original Code and/or Modifications of Original Code
.\" as defined in and that are subject to the Apple Public Source License
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.\" file.
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.\" limitations under the License.
.Dd February 8, 2007
.Os "Mac OS X"
.Nm bootpd
.Nd DHCP/BOOTP/NetBoot server
implements a DHCP/BOOTP server as
defined in RFC951, RFC1542, RFC2131, and RFC2132, as well as a BOOTP/DHCP
relay agent.  It is also a NetBoot server 
implementing Apple-proprietary NetBoot 1.0 (BOOTP-based) and NetBoot 2.0
BSDP (Boot Server Discovery Protocol).  BSDP works along with regular DHCP, 
using DHCP-format packets with a special vendor-class identifier and 
vendor-specific options.
understands and handles requests that arrive via a DHCP/BOOTP relay agent,
allowing the server to be centrally located, and serve many remote subnets.
The server is normally invoked by
.Xr xinetd 8
when a request arrives, 
but can also be invoked manually.  If it is invoked by 
.Xr xinetd 8 ,
continues to service requests until it is idle for a period of 
5 minutes, after which it exits to conserve system resources.  If invoked 
continues to run indefinitely.
receives a SIGHUP (-1) signal, it will re-read its configuration and client
binding files.
When a request from a client arrives, the server logs an entry to 
\fI/var/log/system.log\fR indicating which client made the request, and 
logs another entry once a reply is sent.  This feature can be turned off 
using the 
.Fl q
option described below.
reads its configuration settings from \fI/etc/bootpd.plist\fR.
There are also a number of command-line options to change its behavior on the
fly.  Note in particular that options \fBDmNrS\fR
can also be controlled via service-control properties.  See
.Xr "Service Controls and Filters"
.Bl -tag -width indent
.It Fl B
Disable BOOTP service.  BOOTP is now disabled by default, so specifying
this option has no effect.
.It Fl b
Only respond if the client's bootfile exists: for BOOTP clients only.
.It Fl D
Enable DHCP service.  By default, DHCP service is disabled.
.It Fl d
Remain in the foreground and produce extra debugging output to stderr.
.It Fl I
Disable re-initialization on IP address changes.  By default, 
changes to the server's configured IP addresses cause it to 
.It Fl i Ar "interface"
Enable service on the specified interface.  This flag may appear
multiple times to enable multiple interfaces.   For example, 
    bootpd -i en0 -i en1
to respond only to requests received on
ethernet ports en0 and en1.  By default, all interfaces are enabled.
.It Fl m
Enable NetBoot 1.0 (BOOTP-based) service.
.It Fl N
Enable NetBoot 2.0 (BSDP/DHCP-based) service.
.It Fl o Ar hop_count
For relay agent operation, the maximum hop count, default is 4 hops.
.It Fl q
Be quiet as possible.  Only report serious errors to
.It Fl r Ar server_ip
Relay packets to the specified server_ip, not exceeding the hop count.  
This option can be specified multiple times, one for each server to relay to.
.It Fl S
Enable BOOTP service.
.It Fl v
Be more verbose in messages logged to \fI/var/log/system.log\fR.
reads its configuration from \fI/etc/bootpd.plist\fR\fR, an XML property list.
The root of the property list is a dictionary.  The property list has three main
.Bl -tag -width "Root dictionary"
.It "Root dictionary"
Service Controls and Filters
.It "Subnets"
Subnet Entries
.It "NetBoot"
NetBoot Server Controls
.Ss "Service Controls and Filters"
The root dictionary in \fI/etc/bootpd.plist\fR contains properties to control
will respond to a particular request,   There are MAC address filters,
DHCP controls, as well as controls to enable services.
.Bl -tag -width allow
The MAC address filter properties are:
.It Sy allow
(Array of String) Enables servicing a list of MAC addresses.
.It Sy deny
(Array of String) Disables servicing a list of MAC addresses.
When a packet arrives,
checks whether the client's MAC address is in the deny list.  If it is,
the packet is dropped.  Otherwise, if the client's MAC address is in the allow 
list, the packet continues to be processed, otherwise it is dropped.  If
neither the allow nor the deny property is specified, the packet continues 
to be processed.
.Bl -tag -width old_netboot_enabled
The service-control properties are:
.It Sy bootp_enabled
Enables BOOTP on the specified list of interfaces.
.It Sy dhcp_enabled
Enables DHCP on the specified list of interfaces.
.It Sy netboot_enabled
Enables NetBoot 2.0 (BSDP/DHCP-based) NetBoot on the specified list 
of interfaces.
.It Sy old_netboot_enabled
Enables NetBoot 1.0 (BOOTP-based) NetBoot on the specified list of interfaces.
.It Sy relay_enabled
Enables the relay agent on the specified list of interfaces.  Note that this
option also requires the \fBrelay_ip_list\fR property to be specified.
For each of the properties dhcp_enabled, bootp_enabled,
old_netboot_enabled, netboot_enabled, and relay_enabled, the corresponding
service can be enabled or disabled for all interfaces, or enabled for just
a specific set of interfaces.  To enable or disable globally, use a 
value \fItrue\fR or \fIfalse\fR respectively.
To enable just for a specific set of
interfaces, use either a string, for a single interface, or an array of
strings, one element for each interface.
For example, to enable DHCP on interfaces en0 and en1, disable BOOTP on all
interfaces, enable NetBoot on en1, and enable relay agent on interface en1,
\fI/etc/bootpd.plist\fR could contain:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "">
<plist version="1.0">
.Bl -tag -width detect_other_dhcp_server
Some additional properties are:
.It Sy relay_ip_list
(Array of String) If relay agent functionality is enabled
(see \fBrelay_enabled\fR above), this
property contains the list of IP addresses to relay the packet to.
.It Sy detect_other_dhcp_server
(Boolean) If this property is set to true,
calls exit() if it detects that another DHCP server is present on one of the
interfaces that DHCP is enabled on.  The default value is false.
.It Sy reply_threshold_seconds
won't respond to the request until the bp_secs field is at least 
\fIreply_theshold_seconds\fR.  The default value is 0 (zero).
.It Sy use_open_directory
(Boolean) If this property is set to true,
will look for static IP address to ethernet address bindings in
\fBOpen Directory\fR.  The default value is true.
.It Sy dhcp_ignore_client_identifier
(Boolean) If this property is set to true, the DHCP server tries to
ignore the DHCP client identifier option (code 61) in the client's
DHCP packet.   Instead, the DHCP server tries to use the hardware address
fields (bp_htype, bp_hlen, bp_chaddr) of the DHCP packet to identify the
client.  The default value of this property is false.
.Ss "Subnet Entries"
The "Subnets" property in \fI/etc/bootpd.plist\fR contains an array of 
dictionaries, each dictionary corresponds to a single subnet entry.
A subnet entry describes a range of IP addresses, and associated
information, such as the subnet mask, router, DNS servers, and other
option data.  A subnet entry also indicates whether the range is
an address pool from which to allocate vs. simply an informational range
in order to fulfill requests for option information.  The informational range
is used when the client's IP address binding is static, or the client knows its
own IP address and simply wants relevant option information.
A subnet entry is required to supply the DHCP service with
pool(s) of IP address(es), and to inform the server of subnet-specific
options and parameters.  A subnet entry can also be used to convey network
topology information via the \fBsupernet\fR property described below.
Subnet entries may not overlap in the IP ranges the describe, nor specify 
values that are inconsistent. Specifically, applying the \fBnet_mask\fR value 
to each of the values in the \fBnet_range\fR must yield the 
\fBnet_address\fR value.
Errors in configuration are logged to \fI/var/log/system.log\fR.  There
may be multiple entries for a given subnet, allowing different
configuration values to be specified for a given sub-range of IP addresses
within the subnet.  For example, part of the range might be used for
statically bound clients, and another for a dynamic address pool.
Each subnet entry is encoded as a dictionary with the following
.Bl -tag -width client_types
.It Sy name
(String) A descriptive name for the subnet, e.g. "17.202.40/22".
.It Sy net_mask
(String) The network mask, e.g. "".
This property is required.
.It Sy net_address
(String) The network address, e.g. "".
This property is required.
.It Sy net_range
(Array of String) The network address range stored as two values: 
the first IP address and the last IP address.  For example:
This property is required.
.It Sy allocate
(Boolean) Indicates whether the DHCP service should allocate IP addresses
from the range specified by \fBnet_range\fR.  A \fItrue\fR value means
allocate IP addresses, otherwise, the subnet entry is informational only.
.It Sy lease_min
(Integer) The minimum allowable lease time (in seconds). This property is
ignored unless \fBallocate\fR specifies \fItrue\fR.  
Default value is 3600 (one hour).
.It Sy lease_max
(Integer) The maximum allowable lease time (in seconds). This property is
ignored unless \fBallocate\fR specifies \fItrue\fR.
Default value is 3600 (one hour).
.It Sy supernet
(String) This property indicates that the subnet is on the same physical
broadcast domain as other subnets with the same supernet value.
The server can also supply clients with the following DHCP option
.Bl -tag -width client_types
.It Sy dhcp_router
The IP address of the default router (DHCP option code 3).  If this
property is not present, the server will attempt to provide its own
default route for this option, if it is applicable.
.It Sy dhcp_domain_name_server
The IP address(es) of the DNS server(s) (option code 6).  If this
property is not present, the server will supply its own DNS server 
configuration (if available).
.It Sy dhcp_domain_name
The default DNS domain name (option code 15).  If this property is not
present, the server will supply its own default domain name (if available).
.It Sy dhcp_domain_search
The domain search list (option code 119).  If this property is not
present, the server will supply its domain search list (if available).
.It Sy dhcp_ldap_url
The default LDAP URL (option code 95).
.It Sy dhcp_netinfo_server_address
The NetInfo parent server IP address(es) (option code 112).
.It Sy dhcp_netinfo_server_tag
The NetInfo parent domain tag (option code 113).
.It Sy dhcp_url
The default URL to present in a web browser (option code 114).
.It Sy dhcp_time_offset
The time offset from GMT in seconds (option code 2).
.It Sy dhcp_network_time_protocol_servers
The network time protocol (NTP) server IP address(es) (option code 42).
.It Sy dhcp_nb_over_tcpip_name_server
The NetBIOS over TCP/IP name server IP address(es) (option code 44).
.It Sy dhcp_nb_over_tcpip_dgram_dist_server
The NetBIOS over TCP/IP datagram distribution server IP address(es)
(option code 45).
.It Sy dhcp_nb_over_tcpip_node_type
The NetBIOS over TCP/IP node type (option code 46).
.It Sy dhcp_nb_over_tcpip_scope
The NetBIOS over TCP/IP scope string (option code 47).
.It Sy dhcp_smtp_server
The Simple Mail Transport Protocol (SMTP) server IP address(es)
(option code 69).
.It Sy dhcp_pop3_server
The Post Office Protocol (POP3) server IP address(es) (option code 70).
.It Sy dhcp_nntp_server
The Network News Transport Protocol (NNTP) server IP address(es)
(option code 71).
.It Sy dhcp_proxy_auto_discovery_url
The default Web Proxy Auto Discovery URL (option code 252).
DHCP options may also be specified using the naming convention:
replacing \fIoption_code\fR with a numeric value in the range of 1 through
254.  For example, to specify option code 128, specify a property named
has a built-in type conversion table for many more options, mostly those
specified in RFC 2132, and will try to convert from whatever type the
option appears in the property list to the binary, packet format.  For example,
knows that the type of the option is an IP address or list of IP addresses, it
converts from the string form of the IP address to the binary, network
byte order numeric value.
If the type of the option is a numeric value, it converts from string,
integer, or boolean, to the proper sized, network byte-order numeric value.
Regardless of whether
knows the type of the option or not, you can always specify the DHCP option
using the \fIdata\fR property list type  e.g.:
.Ss "NetBoot Server Controls"
The "NetBoot" property in \fI/etc/bootpd.plist\fR is encoded as a dictionary,
and may contain a number of properties that alter the NetBoot
server's default behavior.  The properties are:
.Bl -tag -width machine_name_format
.It Sy afp_uid_start
(Integer) The starting uid used when creating AFP machine users. The default is 
uid 100.
.It Sy afp_users_max
(Integer) The number of AFP machine users to automaticaly create.
The default is 50.  
Note: the server will never remove a user once it is created, so decreasing
this value once the server has read it will have no effect.
.It Sy age_time_seconds
(Integer) The number of seconds since the client last netbooted before 
before the client is considered "aged".  A client that has aged becomes
 available for resource reclamation.  The server will only reclaim aged
client bindings when it runs out of free resources.
.It Sy machine_name_format
(String) This property is used to generate a unique name to each NetBoot
client. The default value is "NetBoot%03d" (without the double quotes).
The format string must be a 
.Xr printf 3
compatible format string that takes a single integer value as an argument.
The server ensures that the string is valid by testing the string before 
using it.  The only conversion specifiers that should be used are
.It Sy shadow_size_meg
(Integer) The size (in megabytes) to allocate for the client shadow file.
The default is 48 (megabytes).  See 
.Xr "Diskless Resources"
Static IP address to ethernet address bindings are stored in the
\fI/etc/bootptab\fR file and in \fBOpen Directory\fR.
Bindings specified in the \fI/etc/bootptab\fR file take
precedence over those in \fBOpen Directory\fR.
.Xr bootptab 5
for more information about the \fI/etc/bootptab\fR file.
For \fBOpen Directory\fR,
looks at the /Computers records for the following properties:
.Bl -tag -width IPAddressAndENetAddress
.It Sy ENetAddress
(String) The ethernet MAC address(es) of the computer.
Each address must be of the form xx:xx:xx:xx:xx:xx using only the
characters 0123456789abcdef.
Leading zeros must be specified.
.It Sy IPAddress
(String) The IP address(es) of the computer.
.It Sy IPAddressAndENetAddress
(String) Pairs of IP and Ethernet MAC addresses of the computer.  Each
address pair consists of an single IP and MAC address separated by a
slash character, e.g. "".
This attribute should be provided when multiple addresses are provided
because not all directories return attribute values in a guaranteed order.
.It Sy BootFile
(String) The bootfile to use for this computer.
If DHCP service is enabled for a client, the server processes the client's
packet.  The packet may be a request for an IP address and option information
(DHCP Discover, DHCP Request) or for just option information 
(DHCP Inform).  The packet might also tell the server that the address is 
in use by some other host (DHCP Decline), or that the client is done with
the IP address (DHCP Release).
The server uses the DHCP client identifier (option 61) if it is present
as the unique client identifier, otherwise it uses the htype/hlen/chaddr
fields in the DHCP packet.
.Ss "IP Allocation"
The DHCP server first tries to find a static binding for the client (see section
above).  If one exists, it uses it.  If not, it tries to find an existing 
dynamic binding from its lease database, stored in /var/db/dhcpd_leases.  
If one exists and it is applicable to the subnet, the server uses it,
otherwise, it tries to allocate an address from one of its address pools.
If an address is available, the server uses it, otherwise the packet is
After a suitable IP address is found for the client, the server attempts to
insert as many of the requested DHCP options from the client's request as it
can into the reply.
When the server allocates an address dynamically, it automatically excludes
addresses that appear in static host entries.  For example, if
the address range goes from through, but there is
a static entry that specifies, that address is automatically excluded
from the pool.
The server tries to give the same address back to a client by remembering
the binding even after it has expired.  The server removes an expired lease
entry only when it runs out of addresses, and needs to reclaim an address
in order to fulfill a new request.
When the server receives a DHCP Release packet, it sets the expiration for that
lease to now, so that it can immediately reclaim the address if needed.
When the server receives a DHCP Decline packet, it removes the client binding
from the IP address, and sets the expiration on the "unbound" lease to
10 minutes from now.  That allows the address to return to the address 
pool again without manual intervention and avoids handing out the same
in-use IP address over and over.
The NetBoot server enables a client to perform a network boot, that is,
access its operating system image over the network instead of from its
local drive.
The sequence of events that occur when a NetBoot client is powered are:
.Bl -tag -width xxxx
.It 1.
firmware gets IP address and image information (using BOOTP, or BSDP/DHCP)
.It 2.
firmware saves relevant packet(s) in memory to be used by client operating 
system (see step 4 below)
.It 3.
firmware TFTP's the bootfile image, and begins executing it
.It 3.1.
(Mac OS X only) secondary loader TFTP's kernel and drivers, and begins
executing the kernel
.It 4.
client operating system initializes its network stack and accesses its 
"root" disk using information in packets saved at step 2, uses AFP,
NFS, or HTTP to access the image
Apple NetBoot uses a technique called "shadowing", whereby an otherwise 
read-only disk image appears to the client as a read/write image by 
"mapping" writes to the original image file to an auxilliary "shadow" file.
Subsequent reads from portions that have been written also come from the
"shadow" file.  The disk image driver in the client operating system manages
the shadow mapping and provides the illusion of a writable disk.
The term diskless NetBoot implies that the client receives all of its
necessary booting resources from the network, so that a local disk drive is not
required, though may still be present.
The NetBoot server supplies a NetBoot client with the resources and
information it needs to boot.  Two versions of NetBoot
are supported: NetBoot 1.0 (BOOTP-based) and NetBoot 2.0 (BSDP/DHCP-based).
Service for these two types of NetBoot are controlled individually
using command-line options \fBm\fR and \fBN\fR, 
or using the service configuration properties \fBold_netboot_enabled\fR
and \fBnetboot_enabled\fR (described above).
The NetBoot 1.0 server supplies the client with
its IP address in addition to its boot resources.  The server
must be able to find a static binding for the client (see
above), or the server must have an applicable dynamic pool of IP addresses, 
just as with DHCP.  If the server does not also have DHCP service enabled, 
the pools are only used for NetBoot 1.0 clients.  In this case, the server 
also acts as a DHCP server but only services those clients for which it has an 
existing binding.
There can only be one NetBoot 1.0
server per subnet because the protocol uses BOOTP, and BOOTP does not
support multiple servers.  However, the NetBoot 1.0 server will co-exist
with an existing DHCP server, assuming it only serves DHCP.
The NetBoot 2.0 server only supplies the client with boot resources.
Unlike NetBoot 1.0, there is no limit on the number of NetBoot servers
per subnet.
The NetBoot server stores a list of NetBoot client records in the file
/var/db/bsdpd_clients.  Each client record contains the client name and
number assigned by the server, the boot image ID selected by the client,
and the client's last boot time.
.Ss NetBoot Image Location
When the NetBoot server initializes, it looks for NetBoot images
at well-known locations in the file system.  A "NetBoot image" is a 
directory that ends in the .nbi extension, and contains a valid set of files
(described below).
If no images are found, NetBoot is temporarily disabled.  If it receives a
SIGHUP signal, the server again attempts to initialize itself.
The NetBoot server looks for a symbolic link named:
at the root of each local volume.  If the symlink is valid, and points to 
a directory, it assumes that the directory contains NetBoot images and 
that the contents are accessible via TFTP, AFP, NFS, and HTTP.  By convention,
the directory is named:
where x is a unique number starting at zero (0).
.Ss "NetBoot Image (.nbi)"
A NetBoot Image is stored in a directory whose name ends with .nbi, and contains
a set of files.  The directory must contain an NBImageInfo.plist file,
one or more bootfiles, and may contain one or more image files.  
The NBImageInfo.plist file is encoded as an XML property list, and 
contains information about the image.
The properties defined in the NBImageInfo.plist file and their meanings
.Bl -tag -width SupportsDiskless
.It Sy Name
(String) The name of the image that appears in the Startup Disk UI.
.It Sy BootFile
(String) The path of the first bootfile, relative to either the .nbi directory
(for architecture "ppc" only), or a sub-directory of the .nbi directory. 
The sub-directory names correspond to the \fBArchitectures\fR that the
NetBoot Image supports.  See also the \fBArchitectures\fR property below.
.It Sy IsEnabled
(Boolean) A flag to mark the image as enabled or not.  An image that is
disabled will not be offered as a selection by the NetBoot server. Optional,
default value is true.
.It Sy IsDefault
(Boolean) A flag to mark the image as a default image.  Setting this key
to true for more than one image can be useful if the
.Sy EnabledSystemIdentifiers
property is also defined (see below).  Optional, default value is false.
.It Sy IsInstall
(Boolean) A flag to indicate that the image describes an installation
image.  Optional, default value is false.
.It Sy Type
(String) The expected image contents and the mechanism used to
supply images to the client.  The defined values are:
.Bl -tag -width BootFileOnly
.It Classic
After downloading the boot file via TFTP, the client OS accesses its images
via AFP.  The \fBSharedImage\fR and \fBPrivateImage\fR properties 
(defined below) specify the images to use.
After downloading the boot files via TFTP, the client OS accesses its "root"
filesystem via NFS.  The \fBRootPath\fR property (detailed below)
specifies the path.
After downloading the boot files via TFTP, the client accesses its "root"
filesystem via HTTP.  The \fBRootPath\fR property (detailed below)
specifies the path.
.It BootFileOnly
The client downloads the boot file(s), and does not require any 
additional boot image information.
.It Sy Kind
(Integer) The defined image kind values are:
.Bl -tag -width xxx -compact
.It 0 = 
Mac OS 9
.It 1 = 
Mac OS X
.It 2 = 
Mac OS X Server
.It 3 =
Hardware Diagnostics
The default \fBKind\fR is determined from the \fBType\fR:
.Bl -tag -width BootFileOnly -compact
.It \fBType\fR
\fBDefault Kind\fR
.It Classic
0 - Mac OS 9
.It NFS 
1 - Mac OS X
1 - Mac OS X
.It BootFileOnly
The \fBKind\fR must be specified if the \fBType\fR is \fBBootFileOnly\fR.
.It Sy Index
(Integer) The index of the image.  This is a 16-bit value used to differentiate
between multiple NetBoot images supplied by a server.  There are two value
.Bl -tag -compact -width 4096XXXX65535
.It 1 .. 4095
Image is local to this server.
.It 4096 .. 65535
Image is global and may appear on multiple servers, used for load-balancing.
The \fBIndex\fR forms the lower 16-bits of the 
unique 32-bit Image ID.  \fBIsInstall\fR and \fBKind\fR make up the
remaining bits (with 8 bits reserved).
.It Sy RootPath
(String) If Type is "NFS", this is the path of the "root" disk image relative
to the .nbi directory.  The NetBoot server assumes that the path up to and
including the NetBootSPx directory is exported via NFS.
Indirect NFS paths are also supported using the syntax:
    <path> = <host>:<mount_path>[:<image_path>]
    <host> = <IP address> | <host_name>
For example, in the path:
the image is on a server named "myserver" with NFS export "/NetBoot" and 
the image file appears relative to the mount point as "Images/Jaguar.dmg".
If Type is "HTTP", this is the path of the "root" disk image relative
to the .nbi directory.  The NetBoot server assumes that the .nbi directory
under NetBootSPx is exported via HTTP using the convention:
Indirect HTTP paths are also supported using the HTTP URL syntax:
    <path> = http://[<user>@]<host>[:<port>]/<image_path>
    <user> = <user_name>:<password>
    <host> = <IP address> | <host_name>
.It Sy SharedImage
(String) If Type is "Classic", this is the path of the read/write system
disk image used for Mac OS 9.
.It Sy PrivateImage
(String) If Type is "Classic", this is the path of the read-only private
disk image used to store additional applications for Mac OS 9.
.It Sy SupportsDiskless
(Boolean) A flag that indicates that the image supports diskless clients,
and tells the server to allocate resources.  If the Type is "Classic", 
the value of this property is ignored since the server always allocates
resources required for diskless clients.  See Diskless Resources below.
.It Sy EnabledSystemIdentifiers
(Array of String) The list of system identifiers that are enabled for
this image.  The system identifier for Apple hardware is the model
property from the Open Firmware device-tree.  Some example model properties are
"PowerMac3,3" and "PowerBook3,1".
If this property is not specified, or the list is empty, the image is enabled 
for all clients (the default).
If the server has no images that apply to the client, it will not respond.
Due to limitations in the NetBoot 1.0 protocol, there is no way for
the NetBoot server to differentiate between older clients such as the 
original bondi-blue iMac or B&W G3 (Yosemite).  To enable an image for all
NetBoot 1.0 clients, include the pseudo system identifier "/NetBoot1".
.It Sy Architectures
(Array of String) The list of architectures that this image supports.  
Optional, implicit value is an array with a single value "ppc".
The NetBoot server uses the following logic in conjunction with the (explicit or
implicit) value of the \fBArchitectures\fR property and the \fBBootFile\fR
bootfile = plist.BootFile.string
for i = 0; i < plist.Architectures.array.count; i++
    arch = plist.Architectures.array.value[i].string
    if $arch/$bootfile exists
        use $arch/$bootfile
    else if $arch == "ppc" and $bootfile exists
        use $bootfile
        reject this image
That is, for each \fIarchitecture\fR in the \fBArchitectures\fR list
look for a sub-directory of the .nbi directory named \fIarchitecture\fR. 
If the \fBBootFile\fR exists within that directory, continue with the next
\fIarchitecture\fR.  Otherwise, if the \fIarchitecture\fR is "ppc", 
and the \fBBootFile\fR exists directly within the .nbi directory, continue
with the next \fIarchitecture\fR.  Otherwise, reject the image.  If all
\fBArchitectures\fR have a valid \fBBootFile\fR, accept the image.
This logic allows a single-architecture, "ppc"-only NetBoot Image
to work as before.  The directory structure ensures that a
NetBoot Image that only supports non-"ppc" architectures will be 
rejected by a NetBoot server that doesn't understand the \fBArchitectures\fR
property.  This is important because older NetBoot servers only serve
"ppc" images, and they must not mistakenly serve a non-"ppc" image to a
"ppc" client.
.It Sy EnabledMACAddresses
(Array of String) The exclusive list of MAC addresses for
which this image is enabled.  A client whose MAC address is on this
list may be offered this image, subject to any other filtering that might be
in effect, e.g. the \fBArchitectures\fR and \fBEnabledSystemIdentifiers\fR
properties.  If this property is not specified, image MAC
address filtering is subject only to the \fBDisabledMACAddresses\fR property, if
specified.  If this property is defined but the array is empty, the image is
.It Sy DisabledMACAddresses
(Array of String) The list of MAC addresses for which this image
is disabled.  A client whose MAC address is on this list will not be
offered this image.  Defining both this property and the
\fBEnabledMACAddresses\fR property at the same time is not generally useful,
but this property takes precedence.  That is, if a client's MAC
address appears in both lists, it is disabled.
.Ss NetBoot Image Example: Mac OS 9
The path to the image directory in this example is:
    /Library/NetBoot/NetBootSP0/Mac OS 9.nbi
This directory contains the following files:
    Mac OS ROM
    NetBoot HD.img
    Applications HD.img
The NBImageInfo.plist contains:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist SYSTEM "file://localhost/System/Library/DTDs/PropertyList.dtd">
<plist version="0.9">
        <string>Mac OS ROM</string>
        <string>Mac OS 9.2</string>
        <string>NetBoot HD.img</string>
        <string>Applications HD.img</string>
The Type is Classic, which means this is a Mac OS 9 NetBoot image, so the 
implied Kind value is 0 (Mac OS 9).  The BootFile property points to 
"Mac OS ROM".  The system image is "NetBoot HD.img".  The read-only
applications image is "Applications HD.img".  The Name of the image is 
"Mac OS 9.2".  IsEnabled is supplied and set to true, so the image is active.
The Index is 4, which means the image is local to this server, and will 
always appear as a unique choice in the client image selection UI.
.Ss NetBoot Image Example: Mac OS X
The path to this example is:
This directory contains:
The NBImageInfo.plist contains:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist SYSTEM "file://localhost/System/Library/DTDs/PropertyList.dtd">
<plist version="0.9">
        <string>Mac OS X (Jaguar)</string>
The Type is NFS, and no Kind is specified, so the server assumes this is
a Mac OS X image with Kind 1.  The BootFile property points to "booter".
Mac OS X uses three separate bootfiles, so the remaining files which must
exist, but are not currently verified to exist by the server, are 
"mach.macosx" and "mach.macosx.mkext".  Those names are non-negotiable, 
since the booter hard-codes those names.  The RootPath property indicates 
that the image file is "Jaguar.dmg".  The Index is 4096, so this is a
global image, that may appear on multiple NetBoot servers.  
If another server serves an image of the same Kind, IsInstall, and Index,
this image may appear as a single choice in client image selection UI.
.Ss NetBoot Image Example: Mac OS X with Multiple Architectures
The path to this example is:
This directory contains:
The NBImageInfo.plist contains:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist SYSTEM "file://localhost/System/Library/DTDs/PropertyList.dtd">
<plist version="0.9">
        <string>Mac OS X (Tiger)</string>
This example shows how a NetBoot Image that supports multiple architectures
is configured.  The bootfiles for "ppc" reside directly within
the .nbi directory, whereas the bootfiles for "i386" reside within a 
sub-directory of the .nbi directory named "i386".  This image is a Mac OS X
installation image that is served over NFS.
.Ss Diskless Resources
The NetBoot server creates and manages per-client AFP user logins as well as 
per-client directories to give each client its own protected resources.
The AFP users are created on the local system with the attribute \fI_creator\fR
set to \fIbsdpd\fR.
When the server initializes, it ensures there are at least 
\fBafp_users_max\fR users with this property.  If there are not, it allocates
new user entries to make up the difference.
Along with the per-client AFP login, the server creates per-client
directories to store the "shadow" files.  The server creates these
directories on each local volume that contains a symbolic link named:
at the root of the volume.  If the symlink is valid, and points to 
a directory, it assumes that the directory should be used for client
files.   It also assumes that the directory is
a valid AFP sharepoint of the same name.  By convention, the directory is named:
where Y is a unique number starting at zero (0).
The server "round-robins" client files across each such directory to distribute
load amongst multiple disk drives to improve overall performance.
When the server responds to the client's NetBoot request, it ensures that the
"shadow" file is preallocated to \fBshadow_size_meg\fR megabytes.  Setting
that property high enough avoids having every client fail if the server
runs out of disk space.   The only clients that fail if the server
runs out of disk space are those that run of of space in their own
pre-allocated "shadow" files.
Note: the server allocates shadow files for Mac OS 9 NetBoot clients 
only on local HFS volumes.
.Xr bootptab 5 ,
.Xr xinetd 8 ,
.Xr tftpd 8 ,
.Xr exports 5