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DHCPD.LEASES(5)		    BSD	File Formats Manual	       DHCPD.LEASES(5)

     dhcpd.leases -- DHCP server lease database

     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 ac-
     quired, 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.

     Lease descriptions	are stored in a	format that is parsed by the same re-
     cursive 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	dura-
     tion of the lease and to whom it is assigned.

     The start and end time of a lease are recorded using the starts and ends

	   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, re-
     gardless 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 spec-
     ified 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	be-
     cause 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 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 ad-
     dress 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 immedi-
     ately assigned to the client.


     dhcp-options(5), dhcpd.conf(5), dhcpd(8)

     R.	Droms, Dynamic Host Configuration Protocol, RFC	2131, March 1997.

     S.	Alexander and R. Droms,	DHCP Options and BOOTP Vendor Extensions, RFC
     2132, March 1997.

     dhcpd(8) was written by Ted Lemon <>	under a	contract with
     Vixie Labs.

     The current implementation	was reworked by	Henning	Brauer

BSD				 July 27, 2015				   BSD


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