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

       dhcpd.leases - DHCP client lease database

       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.

       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.

       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
       protocol 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 starting 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 provided
       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
       identifiers, 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.


       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
       evaluations 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

       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 '|'

       bootp; reserved; These two statements are effectively flags.  If
       present, they indicate that the BOOTP and RESERVED failover flags,
       respectively, 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 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 DBDIR/dhcpd.leases~

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

       dhcpd(8) is maintained by ISC.  Information about Internet Systems
       Consortium can be found at: https://www.isc.org/