DHCPD.LEASES(5) OpenBSD Programmer's Manual DHCPD.LEASES(5)NAMEdhcpd.leases - DHCP client lease database
DESCRIPTION
The Internet Software Consortium DHCP Server keeps a persistent database
of leases that it has assigned. This database is a free-form ASCII file
containing a series of lease declarations. Every time a lease is
acquired, renewed or released, its new value is recorded at the end of
the lease file. So if more than one declaration appears for a given
lease, the last one in the file is the current one.
FORMAT
Lease descriptions are stored in a format that is parsed by the same
recursive descent parser used to read the dhcpd.conf(5) and
dhclient.conf(5) files. Currently, the only declaration that is used in
the dhcpd.leases file is the lease declaration.
lease ip-address { statements... }
Each lease declaration includes the single IP address that has been
leased to the client. The statements within the braces define the
duration of the lease and to whom it is assigned.
The start and end time of a lease are recorded using the ``starts'' and
``ends'' statements:
starts date;
ends date;
Dates are specified as follows:
weekday year/month/day hour:minute:second
The weekday is present to make it easy for a human to tell when a lease
expires - it's specified as a number from zero to six, with zero being
Sunday. The day of week is ignored on input. The year is specified with
the century, so it should generally be four digits except for really long
leases. The month is specified as a number starting with 1 for January.
The day of the month is likewise specified starting with 1. The hour is
a number from 0 to 23, the minute a number from 0 to 59, and the second
also a number from 0 to 59.
Lease times are specified in Coordinated Universal Time (UTC), not in the
local time zone.
The MAC address of the network interface that was used to acquire the
lease is recorded with the hardware statement:
hardware hardware-type mac-address;
The MAC address is specified as a series of hexadecimal octets, separated
by colons.
If the client uses a client identifier to acquire its address, the client
identifier is recorded using the uid statement:
uid client-identifier;
The client identifier is recorded as a series of hexadecimal octets,
regardless of whether the client specifies an ASCII string or uses the
newer hardware type/MAC address format.
If the client sends a hostname using the Client Hostname option, as
specified in some versions of the DHCP-DNS Interaction draft, that
hostname is recorded using the client-hostname statement.
client-hostname "hostname";
If the client sends its hostname using the Hostname option, it is
recorded using the hostname statement.
hostname "hostname";
The DHCP server may determine that a lease has been misused in some way,
either because a client that has been assigned a lease NAKs it, or
because the server's own attempt to see if an address is in use prior to
reusing it reveals that the address is in fact already in use. In that
case, the abandoned statement will be used to indicate that the lease
should not be reassigned.
abandoned;
Abandoned leases are reclaimed automatically. When a client asks for a
new address, and the server finds that there are no new addresses, it
checks to see if there are any abandoned leases, and allocates the least
recently abandoned lease. The standard mechanisms for checking for lease
address conflicts are still followed, so if the abandoned lease's IP
address is still in use, it will be reabandoned.
If a client requests an abandoned address, the server assumes that the
reason the address was abandoned was that the lease file was corrupted,
and that the client is the machine that responded when the lease was
probed, causing it to be abandoned. In that case, the address is
immediately assigned to the client.
FILES
/var/db/dhcpd.leases
SEE ALSOdhcp-options(5), dhcpd.conf(5), dhcpd(8)
RFC 2132, RFC 2131.
AUTHORSdhcpd(8) was written by Ted Lemon <mellon@vix.com> under a contract with
Vixie Labs.
The current implementation was reworked by Henning Brauer
<henning@openbsd.org>.
OpenBSD 4.9 May 31, 2007 OpenBSD 4.9
