261 lines
12 KiB
Groff
261 lines
12 KiB
Groff
.\" dhcpd.leases.5
|
|
.\"
|
|
.\" Copyright (c) 1996-2001 Internet Software Consortium.
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\"
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. Neither the name of The Internet Software Consortium nor the names
|
|
.\" of its contributors may be used to endorse or promote products derived
|
|
.\" from this software without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
|
|
.\" CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
|
|
.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
|
|
.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
.\" DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
|
|
.\" CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
|
.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
|
|
.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
|
|
.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
|
|
.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
|
|
.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" This software has been written for the Internet Software Consortium
|
|
.\" by Ted Lemon in cooperation with Vixie Enterprises and Nominum, Inc.
|
|
.\" To learn more about the Internet Software Consortium, see
|
|
.\" ``http://www.isc.org/''. To learn more about Vixie Enterprises,
|
|
.\" see ``http://www.vix.com''. To learn more about Nominum, Inc., see
|
|
.\" ``http://www.nominum.com''.
|
|
.TH dhcpd.leases 5
|
|
.SH NAME
|
|
dhcpd.leases - DHCP client lease database
|
|
.SH 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.
|
|
.PP
|
|
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:
|
|
.PP
|
|
.nf
|
|
touch DBDIR/dhcpd.leases
|
|
.fi
|
|
.PP
|
|
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.
|
|
.SH FORMAT
|
|
Lease descriptions are stored in a format that is parsed by the same
|
|
recursive descent parser used to read the
|
|
.B dhcpd.conf(5)
|
|
and
|
|
.B 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.
|
|
.PP
|
|
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.
|
|
.PP
|
|
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
|
|
\fIrubout\fR is written to the lease file. This is just the same
|
|
declaration, with \fB{ deleted; }\fR 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 \fBdhcpd.conf\fR file; in this case, the rubout
|
|
can never be eliminated from the \fBdhcpd.leases\fR file.
|
|
.SH THE LEASE DECLARATION
|
|
.PP
|
|
.B lease \fIip-address\fB { \fIstatements...\fB }
|
|
.PP
|
|
Each lease declaration include 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.
|
|
.PP
|
|
.nf
|
|
.B starts \fIdate\fB;\fR
|
|
.B ends \fIdate\fB;\fR
|
|
.B tstp \fIdate\fB;\fR
|
|
.B tsfp \fIdate\fB;\fR
|
|
.fi
|
|
.PP
|
|
The start and end time of a lease are recorded using the \fBstarts\fR
|
|
and \fBends\fR statements. The \fBtstp\fR statement is specified if
|
|
the failover protocol is being used, and indicates what time the peer
|
|
has been told the lease expires. The \fBtsfp\fR statement is
|
|
also specified if the failover protocol is being used, and indicates
|
|
the lease expiry time that the peer has acknowledged. The \fIdate\fR
|
|
is specified as follows:
|
|
.PP
|
|
.I weekday year\fB/\fImonth\fB/\fIday hour\fB:\fIminute\fB:\fIsecond\fR
|
|
.PP
|
|
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.
|
|
.PP
|
|
Lease times are specified in Coordinated Universal 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
|
|
\fBdate -u\fR.
|
|
.PP
|
|
If a lease will never expire, \fIdate\fR is \fBnever\fR instead of an
|
|
actual date.
|
|
.PP
|
|
.B hardware \fIhardware-type mac-address\fB;\fR
|
|
.PP
|
|
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.
|
|
.PP
|
|
.B uid \fIclient-identifier\fB;\fR
|
|
.PP
|
|
The \fBuid\fR 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 \fBhardware\fI
|
|
statement, but this is not required.
|
|
.PP
|
|
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.
|
|
.PP
|
|
.B client-hostname "\fIhostname\fB";\fR
|
|
.PP
|
|
Most DHCP clients will send their hostname in the \fIhost-name\fR
|
|
option. If a client sends its hostname in this way, the hostname is
|
|
recorded on the lease with a \fBclient-hostname\fR statement. This
|
|
is not required by the protocol, however, so many specialized DHCP
|
|
clients do not send a host-name option.
|
|
.PP
|
|
.B abandoned;
|
|
.PP
|
|
The \fBabandoned\fR statement indicates that the DHCP server has
|
|
abandoned the lease. In that case, the \fBabandoned\fR statement
|
|
will be used to indicate that the lease should not be reassigned.
|
|
Please see the \fBdhcpd.conf(5)\fR manual page for information about
|
|
abandoned leases.
|
|
.PP
|
|
.B binding state \fIstate\fB;
|
|
.B next binding state \fIstate\fB;
|
|
.PP
|
|
The \fBbinding state\fR 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 \fBactive\fR or \fBfree\fR. The
|
|
failover protocol adds some additional transitional states, as well as
|
|
the \fBbackup\fR state, which indicates that the lease is available
|
|
for allocation by the failover secondary.
|
|
.PP
|
|
The \fBnext binding state\fR 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 \fIends\fR statement.
|
|
.PP
|
|
.B option agent.circuit-id \fIstring\fR;
|
|
.B option agent.remote-id \fIstring\fR;
|
|
.PP
|
|
The \fBoption agent.circuit-id\fR and \fBoption agent.remote-id\fR
|
|
statements are used to record the circuit ID and remote ID options
|
|
send by the relay agent, if the relay agent uses the \fIrelay agent
|
|
information option\fR. 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.
|
|
.PP
|
|
.B set \fIvariable\fB = \fIvalue\fB;
|
|
.PP
|
|
The \fBset\fR statement sets the value of a variable on the lease.
|
|
For general information on variables, see the \fBdhcp-eval(5)\fR
|
|
manual page.
|
|
.PP
|
|
.B The \fIddns-text\fB variable
|
|
.PP
|
|
The \fIddns-text\fR 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.
|
|
.PP
|
|
.B The \fIddns-fwd-name\fB variable
|
|
.PP
|
|
The \fIddns-fwd-name\fB 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.
|
|
.PP
|
|
.B The \fIddns-client-fqdn\fB variable
|
|
.PP
|
|
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
|
|
\fIddns-client-fqdn\fR 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.
|
|
.PP
|
|
.B The \fIddns-rev-name\fB variable
|
|
.PP
|
|
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
|
|
\fIddns-fwd-name\fR or the \fIddns-client-fqdn\fR.
|
|
.PP
|
|
.B on \fIevents\fB { \fIstatements...\fB }
|
|
The \fBon\fI statement records a list of statements to execute if a
|
|
certain event occurs. The possible events that can occur for an
|
|
active lease are \fBrelease\fR and \fBexpiry\fR. More than one event
|
|
can be specified - if so, the events are separated by '|' characters.
|
|
.SH THE FAILOVER PEER STATE DECLARATION
|
|
The state of any failover peering arrangements is also recorded in the
|
|
lease file, using the \fBfailover peer\fR statement:
|
|
.PP
|
|
.nf
|
|
.B failover peer "\fIname\fB" state {
|
|
.B my state \fIstate\fB at \fIdate\fB;
|
|
.B peer state \fIstate\fB at \fIdate\fB;
|
|
.B }
|
|
.fi
|
|
.PP
|
|
The states of the peer named \fIname\fR is being recorded. Both the
|
|
state of the running server (\fBmy state\fR) and the other failover
|
|
partner (\fIpeer state\fR) are recorded. The following states are
|
|
possible: \fBunknown-state\fR, \fBpartner-down\fR, \fBnormal\fR,
|
|
\fBcommunications-interrupted\fR, \fBresolution-interrupted\fR,
|
|
\fBpotential-conflict\fR, \fBrecover\fR, \fBrecover-done\fR,
|
|
\fBshutdown\fR, \fBpaused\fR, and \fBstartup\fR.
|
|
.B DBDIR/dhcpd.leases
|
|
.SH SEE ALSO
|
|
dhcpd(8), dhcp-options(5), dhcp-eval(5), dhcpd.conf(5), RFC2132, RFC2131.
|
|
.SH AUTHOR
|
|
.B dhcpd(8)
|
|
was written by Ted Lemon
|
|
under a contract with Vixie Labs. Funding
|
|
for this project was provided by the Internet Software Consortium.
|
|
Information about the Internet Software Consortium can be found at:
|
|
.B http://www.isc.org/
|