dhcpd.leases(5) 						File Formats Manual						   dhcpd.leases(5)

NAME

       dhcpd.leases - DHCP client lease database

DESCRIPTION

       The Internet Systems 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.

       When dhcpd is first installed, there is no lease database.   However, dhcpd requires that a lease database be present before it will start.
       To make the initial lease database, just create an empty file called DBDIR/dhcpd.leases.   You can do this with:

	    touch DBDIR/dhcpd.leases

       In order to prevent the lease database from growing without bound, the file is rewritten from time to  time.    First,  a  temporary  lease
       database  is  created  and all known leases are dumped to it.   Then, the old lease database is renamed DBDIR/dhcpd.leases~.   Finally, the
       newly written lease database is moved into place.

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.   Lease  files	can  contain  lease  declarations, and also group and subgroup declarations, host declarations and
       failover state declarations.  Group, subgroup and host declarations are used to record objects created using the OMAPI protocol.

       The lease file is a log-structured file - whenever a lease changes, the contents of that lease are written to the end of the  file.    This
       means that it is entirely possible and quite reasonable for there to be two or more declarations of the same lease in the lease file at the
       same time.   In that case, the instance of that particular lease that appears last in the file is the one that is in effect.

       Group, subgroup and host declarations in the lease file are handled in the same manner, except that if any of these objects are deleted,  a
       rubout  is  written  to	the lease file.   This is just the same declaration, with { deleted; } in the scope of the declaration.   When the
       lease file is rewritten, any such rubouts that can be eliminated are eliminated.   It is possible to delete a declaration in the dhcpd.conf
       file; in this case, the rubout can never be eliminated from the dhcpd.leases file.

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.

       starts date;
       ends date;
       tstp date;
       tsfp date;
       atsfp date;
       cltt date;

       The start and end time of a lease are recorded using the starts and ends statements.   The tstp statement is specified if the failover pro-
       tocol  is  being  used,	and  indicates	what  time the peer has been told the lease expires.   The tsfp statement is also specified if the
       failover protocol is being used, and indicates the lease expiry time that the peer has acknowledged.  The atsfp	statement  is  the  actual
       time sent from the failover partner.  The cltt statement is the client's last transaction time.

       The  date  is specified in two ways, depending on the configuration value for the db-time-format parameter.  If it was set to default, then
       the date fields appear 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 start-
       ing with 1.  The hour is a number between 0 and 23, the minute a number between 0 and 59, and the second also a number between 0 and 59.

       Lease  times  are  specified in Universal Coordinated Time (UTC), not in the local time zone.  There is probably nowhere in the world where
       the times recorded on a lease are always the same as wall clock times.  On most unix machines, you can display the current time in  UTC	by
       typing date -u.

       If the db-time-format was configured to local, then the date fields appear as follows:

	epoch <seconds-since-epoch>; # <day-name> <month-name> <day-number> <hours>:<minutes>:<seconds> <year>

       The  seconds-since-epoch  is  as according to the system's local clock (often referred to as "unix time").  The # symbol supplies a comment
       that describes what actual time this is as according to the system's configured timezone, at the time the value was written.   It  is  pro-
       vided only for human inspection.

       If a lease will never expire, date is never instead of an actual date.

       hardware hardware-type mac-address;

       The  hardware  statement records the MAC address of the network interface on which the lease will be used.   It is specified as a series of
       hexadecimal octets, separated by colons.

       uid client-identifier;

       The uid statement records the client identifier used by the client to acquire the lease.   Clients are not required to send client  identi-
       fiers,  and  this statement only appears if the client did in fact send one.   Client identifiers are normally an ARP type (1 for ethernet)
       followed by the MAC address, just like in the hardware statement, but this is not required.

       The client identifier is recorded as a colon-separated hexadecimal list or as a quoted string.	If it is recorded as a quoted  string  and
       it  contains  one  or  more non-printable characters, those characters are represented as octal escapes - a backslash character followed by
       three octal digits.

       client-hostname hostname ;

       Most DHCP clients will send their hostname in the host-name option.  If a client sends its hostname in this way, the hostname  is  recorded
       on  the	lease  with  a client-hostname statement.   This is not required by the protocol, however, so many specialized DHCP clients do not
       send a host-name option.

       abandoned;

       The abandoned statement indicates that the DHCP server has abandoned the lease.	 In that case, the abandoned statement	will  be  used	to
       indicate that the lease should not be reassigned.  Please see the dhcpd.conf(5) manual page for information about abandoned leases.

       binding state state; next binding state state;

       The  binding  state  statement  declares the lease's binding state.  When the DHCP server is not configured to use the failover protocol, a
       lease's binding state will be either active or free.   The failover protocol adds some additional  transitional	states,  as  well  as  the
       backup state, which indicates that the lease is available for allocation by the failover secondary.

       The  next  binding  state statement indicates what state the lease will move to when the current state expires.	 The time when the current
       state expires is specified in the ends statement.

       option agent.circuit-id string; option agent.remote-id string;

       The option agent.circuit-id and option agent.remote-id statements are used to record the circuit ID and remote ID options send by the relay
       agent, if the relay agent uses the relay agent information option.   This allows these options to be used consistently in conditional eval-
       uations even when the client is contacting the server directly rather than through its relay agent.

       set variable = value;

       The set statement sets the value of a variable on the lease.  For general information on variables, see the dhcp-eval(5) manual page.

       The ddns-text variable

       The ddns-text variable is used to record the value of the client's TXT identification record when the interim ddns update  style  has  been
       used to update the DNS for a particular lease.

       The ddns-fwd-name variable

       The ddns-fwd-name variable records the value of the name used in updating the client's A record if a DDNS update has been successfully done
       by the server.	The server may also have used this name to update the client's PTR record.

       The ddns-client-fqdn variable

       If the server is configured to use the interim ddns update style, and is also configured to allow clients to update their  own  fqdns,  and
       the  client did in fact update its own fqdn, then the ddns-client-fqdn variable records the name that the client has indicated it is using.
       This is the name that the server will have used to update the client's PTR record in this case.

       The ddns-rev-name variable

       If the server successfully updates the client's PTR record, this variable will record the name that  the  DHCP  server  used  for  the  PTR
       record.	 The name to which the PTR record points will be either the ddns-fwd-name or the ddns-client-fqdn.

       The vendor-class-identifier variable

       The  server  retains  the  client-supplied  Vendor Class Identifier option for informational purposes, and to render them in DHCPLEASEQUERY
       responses.

       on events { statements... } The on statement records a list of statements to execute if a certain event occurs.	 The possible events  that
       can occur for an active lease are release and expiry.   More than one event can be specified - if so, the events are separated by '|' char-
       acters.

       bootp; reserved; These two statements are effectively flags.  If present, they indicate that the BOOTP and RESERVED failover flags, respec-
       tively,	should	be set.  BOOTP and RESERVED dynamic leases are treated differently than normal dynamic leases, as they may only be used by
       the client to which they are currently allocated.

THE FAILOVER PEER STATE DECLARATION

       The state of any failover peering arrangements is also recorded in the lease file, using the failover peer statement:

       failover peer name state {
       my state state at date;
       peer state state at date;
       }

       The states of the peer named name is being recorded.   Both the state of the running server (my state) and the other failover partner (peer
       state)  are  recorded.	 The  following  states are possible: unknown-state, partner-down, normal, communications-interrupted, resolution-
       interrupted, potential-conflict, recover, recover-done, shutdown, paused, and startup.  DBDIR/dhcpd.leases

SEE ALSO

       dhcpd(8), dhcp-options(5), dhcp-eval(5), dhcpd.conf(5), RFC2132, RFC2131.

AUTHOR

       dhcpd(8) was written by Ted Lemon under a contract with Vixie Labs.   Funding for this project was provided by Internet Systems Consortium.
       Information about Internet Systems Consortium can be found at: https://www.isc.org/

																   dhcpd.leases(5)