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

NAME
     dhcpd.leases -- DHCP server 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 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
     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 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
     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 immedi-
     ately assigned to the client.

FILES
     /var/db/dhcpd.leases

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

STANDARDS
     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.

AUTHORS
     dhcpd(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>.

BSD                             April 25, 2017                             BSD