Man page of server.pcy
Section: Devices and Network Interfaces (4)
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server.pcy - BOOTP and DHCP server policy
file is a text database that governs the behavior of BOOTP and DHCP servers.
If the joind daemon is invoked to use text databases, it reads
the server.pcy file on startup. If the JOINCONFIG variable is
present in the joind environment, it specifies
the directory for the server.pcy file; otherwise,
joind searches the /etc/join directory.
Defaults exist for all parameters and switches, so it is not an
error if the file does not exist.
Blank lines are ignored. The number sign character (#)
introduces a comment, which continues to the next newline. Each new policy
option must begin and end on a separate line.
Policy options are introduced by a keyword,
and may be Boolean, or may take a value
separated from the keyword by whitespace
(but not a newline). If an option is present
more than once, only the value attached to
the last occurrence
is used; earlier value(s)
Keywords and Values
For each subnet that the BOOTP and DHCP server administers,
two lists are maintained in memory:
a "free" list containing IP addresses available
for allocation and a "provisional" list
containing addresses that have been tentatively
assigned, which are awaiting client
approval in the form of a DHCPREQUEST
The value of seconds determines how long an address will remain
on the free list before the server determines that the client does not
want the offered address. The free list does not
contain every address available to the server;
instead it acts as a cache of addresses
which the server can offer without
reading the disk.
If a new
client makes a DHCPDISCOVER, and no
IP address exists for the client in permanent
store, the server first goes to the free
list for an unused address.
If the free list is exhausted, the server
first reclaims any addresses on
the provisional list which have expired.
It then extends this list to be
free_list_size in length by reading from the disk.
This has a benefit in that addresses
are usually offered in numerically
increasing order. Making the ttl too short will not give clients
an opportunity to confirm offered
addresses; making it too long
will waste memory.
See the explanation under provisional_ttl.
If this number is too low, server
response time will suffer. If
it is too large it has the undesirable
effect of requiring the server
to reclaim expired leases before they
are actually needed for reallocation
to new clients. Although this is not
an error, a desirable feature of server
operation is that, whenever possible,
a client requesting a new IP address
should get back its old address, unless
that address has been leased to a new client.
This and the "assign_name_by_ipaddr" option are mutually exclusive.
They govern how the server assigns names to hosts.
This option tells the server to bind a name
to the MAC address. That way, if the client
moves to a new address, it keeps the same
This tells the server that if a lookup to
the name service (gethostbyaddr(3))
succeeds, the client should receive the
name that was found at the IP address.
This Boolean option is compatible
with previous options. It instructs
the server that if it is not able
to find a name for the client by application
of the two previous policies, it can
accept the name the client suggests for itself
providing that this is not in contradiction with values currently in the name
service. If a contradiction exists, or this policy is not enabled,
joind consults its namepool or prefix.
This Boolean tells joind
to support BOOTP clients. When replying to
BOOTP clients, the server does not use the
DHCP extensions to the BOOTP protocol.
This is enabled by default.
This Boolean is only valid if the support_bootp option is enabled.
When on support_bootp permits the server to permanently assign
an IP address from its free pool to a BOOTP client in the event that no
permanent binding exists in bootptab. Normally the BOOTP and DHCP server can only service BOOTP clients for which such a binding pre-exists.
Before the server offers an IP address to a client
it may first check that the address is not in use
by sending an ICMP echo request. If an echo is
received, it means that the address is in use, and
the server selects another. This parameter
specifies the time (in milliseconds) that the
server waits for the echo. If this value
is zero or negative, the server does not perform
this check. Disabling this check may be necessary
in certain environments to decrease server response
time to an acceptable level; this release of
joind is not multithreaded, so the server idles while
awaiting the response.
Specifications: RFC 1541, RFC 1542
- Keywords and Values
- RELATED INFORMATION
This document was created by
using the manual pages.
Time: 02:40:08 GMT, October 02, 2010