


dhcpd.leases(5)                                   dhcpd.leases(5)


NNAAMMEE
       dhcpd.leases - DHCP client lease database

DDEESSCCRRIIPPTTIIOONN
       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
       /var/db/dhcpd.leases.   You can do this with:

            touch /var/db/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  /var/db/dhcpd.leases~.    Finally,  the
       newly written lease database is moved into place.

FFOORRMMAATT
       Lease  descriptions  are  stored in a format that is parsed by the same
       recursive  descent  parser  used  to   read   the   ddhhccppdd..ccoonnff((55))   and
       ddhhcclliieenntt..ccoonnff((55))  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
       _r_u_b_o_u_t  is  written to the lease file.   This is just the same declara-
       tion, with {{ ddeelleetteedd;; }} 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  ddhhccppdd..ccoonnff
       file;  in  this  case,  the  rubout  can  never  be eliminated from the
       ddhhccppdd..lleeaasseess file.

TTHHEE LLEEAASSEE DDEECCLLAARRAATTIIOONN
       lleeaassee _i_p_-_a_d_d_r_e_s_s {{ _s_t_a_t_e_m_e_n_t_s_._._. }}

       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.



                                                                1





dhcpd.leases(5)                                   dhcpd.leases(5)


       ssttaarrttss _d_a_t_e;;
       eennddss _d_a_t_e;;
       ttssttpp _d_a_t_e;;
       ttssffpp _d_a_t_e;;

       The start and end time of a lease are recorded  using  the  ssttaarrttss  and
       eennddss statements.   The ttssttpp statement is specified if the failover pro-
       tocol is being used, and indicates what time the peer has been told the
       lease  expires.    The ttssffpp statement is also specified if the failover
       protocol is being used, and indicates the lease expiry  time  that  the
       peer has acknowledged.

       The _d_a_t_e is specified in two ways, depending on the configuration value
       for the ddbb--ttiimmee--ffoorrmmaatt parameter.  If it was set to _d_e_f_a_u_l_t,  then  the
       _d_a_t_e fields appear as follows:

       _w_e_e_k_d_a_y _y_e_a_r//_m_o_n_t_h//_d_a_y _h_o_u_r::_m_i_n_u_t_e::_s_e_c_o_n_d

       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
       ddaattee --uu.

       If the ddbb--ttiimmee--ffoorrmmaatt was configured to _l_o_c_a_l,  then  the  _d_a_t_e  fields
       appear as follows:

        eeppoocchh  _<_s_e_c_o_n_d_s_-_s_i_n_c_e_-_e_p_o_c_h_>;;  ##  _<_d_a_y_-_n_a_m_e_> _<_m_o_n_t_h_-_n_a_m_e_> _<_d_a_y_-_n_u_m_b_e_r_>
       _<_h_o_u_r_s_>::_<_m_i_n_u_t_e_s_>::_<_s_e_c_o_n_d_s_> _<_y_e_a_r_>

       The _s_e_c_o_n_d_s_-_s_i_n_c_e_-_e_p_o_c_h 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, _d_a_t_e is nneevveerr instead of an actual  date.

       hhaarrddwwaarree _h_a_r_d_w_a_r_e_-_t_y_p_e _m_a_c_-_a_d_d_r_e_s_s;;

       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  hex-
       adecimal octets, separated by colons.

       uuiidd _c_l_i_e_n_t_-_i_d_e_n_t_i_f_i_e_r;;



                                                                2





dhcpd.leases(5)                                   dhcpd.leases(5)


       The  uuiidd  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 hhaarrddwwaarree _s_t_a_t_e_m_e_n_t_, _b_u_t
       _t_h_i_s _i_s _n_o_t _r_e_q_u_i_r_e_d_.

       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.

       cclliieenntt--hhoossttnnaammee _h_o_s_t_n_a_m_e ;;

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

       aabbaannddoonneedd;;

       The aabbaannddoonneedd statement indicates that the DHCP  server  has  abandoned
       the  lease.    In  that  case,  the aabbaannddoonneedd statement will be used to
       indicate that the lease should  not  be  reassigned.   Please  see  the
       ddhhccppdd..ccoonnff((55)) manual page for information about abandoned leases.

       bbiinnddiinngg ssttaattee _s_t_a_t_e;; nneexxtt bbiinnddiinngg ssttaattee _s_t_a_t_e;;

       The  bbiinnddiinngg  ssttaattee 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 aaccttiivvee or ffrreeee.   The failover
       protocol adds some additional  transitional  states,  as  well  as  the
       bbaacckkuupp  state,  which indicates that the lease is available for alloca-
       tion by the failover secondary.

       The nneexxtt bbiinnddiinngg ssttaattee 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 _e_n_d_s statement.

       ooppttiioonn aaggeenntt..cciirrccuuiitt--iidd _s_t_r_i_n_g; ooppttiioonn aaggeenntt..rreemmoottee--iidd _s_t_r_i_n_g;

       The ooppttiioonn aaggeenntt..cciirrccuuiitt--iidd and ooppttiioonn aaggeenntt..rreemmoottee--iidd  statements  are
       used  to  record the circuit ID and remote ID options send by the relay
       agent, if the relay agent uses  the  _r_e_l_a_y  _a_g_e_n_t  _i_n_f_o_r_m_a_t_i_o_n  _o_p_t_i_o_n.
       This allows these options to be used consistently in conditional evalu-
       ations even when the client is contacting the  server  directly  rather
       than through its relay agent.

       sseett _v_a_r_i_a_b_l_e == _v_a_l_u_e;;

       The  sseett statement sets the value of a variable on the lease.  For gen-
       eral information on variables, see the ddhhccpp--eevvaall((55)) manual page.



                                                                3





dhcpd.leases(5)                                   dhcpd.leases(5)


       TThhee _d_d_n_s_-_t_e_x_t vvaarriiaabbllee

       The _d_d_n_s_-_t_e_x_t 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.

       TThhee _d_d_n_s_-_f_w_d_-_n_a_m_e vvaarriiaabbllee

       The _d_d_n_s_-_f_w_d_-_n_a_m_e vvaarriiaabbllee rreeccoorrddss tthhee vvaalluuee ooff tthhee nnaammee uusseedd iinn uuppddaatt--
       iinngg  tthhee  cclliieenntt''ss AA rreeccoorrdd iiff aa DDDDNNSS uuppddaattee hhaass bbeeeenn ssuucccceessssffuullllyy ddoonnee
       bbyy tthhee sseerrvveerr..   TThhee sseerrvveerr mmaayy aallssoo hhaavvee uusseedd tthhiiss nnaammee ttoo uuppddaattee  tthhee
       cclliieenntt''ss PPTTRR rreeccoorrdd..

       TThhee _d_d_n_s_-_c_l_i_e_n_t_-_f_q_d_n vvaarriiaabbllee

       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 _d_d_n_s_-_c_l_i_e_n_t_-_f_q_d_n vari-
       able 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.

       TThhee _d_d_n_s_-_r_e_v_-_n_a_m_e vvaarriiaabbllee

       If the server successfully updates the client's PTR record, this  vari-
       able 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  _d_d_n_s_-_f_w_d_-
       _n_a_m_e or the _d_d_n_s_-_c_l_i_e_n_t_-_f_q_d_n.

       oonn  _e_v_e_n_t_s  {{ _s_t_a_t_e_m_e_n_t_s_._._. }} The oonn _s_t_a_t_e_m_e_n_t _r_e_c_o_r_d_s _a _l_i_s_t _o_f _s_t_a_t_e_-
       _m_e_n_t_s _t_o _e_x_e_c_u_t_e _i_f _a _c_e_r_t_a_i_n _e_v_e_n_t _o_c_c_u_r_s_.   _T_h_e _p_o_s_s_i_b_l_e _e_v_e_n_t_s  _t_h_a_t
       _c_a_n  _o_c_c_u_r  _f_o_r _a_n _a_c_t_i_v_e _l_e_a_s_e _a_r_e rreelleeaassee and eexxppiirryy.   More than one
       event can be specified - if so, the events are separated by '|' charac-
       ters.

       bboooottpp;;  rreesseerrvveedd;;  These two statements are effectively flags.  If pre-
       sent, 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.

TTHHEE FFAAIILLOOVVEERR PPEEEERR SSTTAATTEE DDEECCLLAARRAATTIIOONN
       The  state of any failover peering arrangements is also recorded in the
       lease file, using the ffaaiilloovveerr ppeeeerr statement:

       ffaaiilloovveerr ppeeeerr _n_a_m_e ssttaattee {{
       mmyy ssttaattee _s_t_a_t_e aatt _d_a_t_e;;
       ppeeeerr ssttaattee _s_t_a_t_e aatt _d_a_t_e;;
       }}

       The states of the peer named _n_a_m_e is being recorded.   Both  the  state
       of  the  running server (mmyy ssttaattee) and the other failover partner (_p_e_e_r
       _s_t_a_t_e) are recorded.   The  following  states  are  possible:  uunnkknnoowwnn--
       ssttaattee,  ppaarrttnneerr--ddoowwnn,  nnoorrmmaall,  ccoommmmuunniiccaattiioonnss--iinntteerrrruupptteedd, rreessoolluuttiioonn--



                                                                4





dhcpd.leases(5)                                   dhcpd.leases(5)


       iinntteerrrruupptteedd,  ppootteennttiiaall--ccoonnfflliicctt,  rreeccoovveerr,   rreeccoovveerr--ddoonnee,   sshhuuttddoowwnn,
       ppaauusseedd, and ssttaarrttuupp.  //vvaarr//ddbb//ddhhccppdd..lleeaasseess

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

AAUUTTHHOORR
       ddhhccppdd((88)) 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:
       hhttttppss::////wwwwww..iisscc..oorrgg//













































                                                                5


