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.Dd $Mdocdate: December 17 2019 $
.Dt DHCLIENT.CONF 5
.Os
.Sh NAME
.Nm dhclient.conf
.Nd DHCP client configuration file
.Sh DESCRIPTION
.Nm
is the configuration file for
.Xr dhclient 8 .
It is a free-form ASCII text file made up of declarations, extra
tabs and newlines for formatting purposes and comments.
Keywords in the file are case-insensitive.
Comments begin with the
.Sq #
character and extend to the end of the current line.
.Sh PROTOCOL TIMING DECLARATIONS
.Bl -tag -width Ds
.It Ic backoff-cutoff Ar seconds ;
Sets the maximum number of seconds to
wait before retransmitting a packet.
The default is 10 seconds.
.It Ic initial-interval Ar seconds ;
Sets the number of seconds between the first packet transmission
and the first retransmission of the packet.
The default is 1 second.
.It Ic link-timeout Ar seconds ;
Sets the number of seconds
to wait for a lease before going into the background as a daemon.
The default is 10 seconds.
.It Ic reboot Ar seconds ;
Sets the number of seconds to wait
before giving up on reacquiring the previous lease, and how long
to attempt unicast renewal requests before falling back to broadcast
renewal requests.
The default is 1 second.
.It Ic retry Ar seconds ;
Sets the number of seconds to wait before starting a new attempt to
obtain a lease.
The default is 1 second.
.It Ic select-timeout Ar seconds ;
Sets the number of seconds to wait for additional leases after the
first lease arrives.
After
.Ic select-timeout
seconds the best lease received will be selected.
The default is 0 seconds, i.e. immediately use
the first acceptable lease received.
.It Ic timeout Ar seconds ;
Sets the number of seconds to wait for a lease.
If no lease is received the first valid lease in
.Xr dhclient.leases 5
will be used.
The default is 30 seonds.
.El
.Sh DHCP OPTION DECLARATIONS
.Bl -tag -width Ds
.It Ic append Ar option option-value ;
Append
.Ar option-value
to the value of
.Ar option
in the lease.
Each
.Ic append
for
.Ar option
overrides any previous
.Ic append ,
.Ic default ,
.Ic ignore ,
.Ic prepend
or
.Ic supersede
for
.Ar option .
.Pp
If the option's data cannot be appended to, i.e. it has a fixed size,
then
.Ic append
will be treated as
.Ic default .
.It Ic default Ar option option-value ;
If no value for
.Ar option
is present in the lease use
.Ar option-value .
Each
.Ic default
for
.Ar option
overrides any previous
.Ic append ,
.Ic default ,
.Ic ignore ,
.Ic prepend
or
.Ic supersede
for
.Ar option .
.It Ic ignore Op Ar option , ... ;
Discard values provided for the listed options.
.Ic ignore
statements are cumulative, except that an empty
list will remove all previously specified options.
Each
.Ic ignore
for
.Ar option
overrides any previous
.Ic append ,
.Ic default ,
.Ic prepend
or
.Ic supersede
for
.Ar option .
.It Ic prepend Ar option option-value ;
Prepend
.Ar option-value
to the value of
.Ar option
in the lease.
Each
.Ic prepend
for
.Ar option
overrides any previous
.Ic append ,
.Ic default ,
.Ic ignore ,
.Ic prepend
or
.Ic supersede
for
.Ar option .
.Pp
If the option's data cannot be prepended to, i.e. it has a fixed size,
then
.Ic prepend
will be treated as
.Ic supersede .
.It Ic request Op Ar option , ... ;
Ask that any lease contain values
for the listed options.
.Ic request
statements are cumulative, except that an empty
list will remove all previously specified options.
The default is to request the options
bootfile-name,
broadcast-address,
classless-static-routes,
host-name,
domain-name,
domain-name-servers,
domain-search,
routers,
subnet-mask,
tftp-server-name
and
time-offset.
.It Ic require Op Ar option , ... ;
Discard leases that do not contain the listed options.
.Ic require
statements are cumulative, except that an empty
list will remove all previously specified options.
The default is to require the option subnet-mask.
.It Ic send Ar option option-value ;
Include
.Ar option-value
in requests for a lease.
To include multiple options in requests,
.Ic send
can be used multiple times.
.It Ic supersede Ar option option-value ;
Use
.Ar option-value
for the given
.Ar option
regardless of the value in the lease.
Each
.Ic supersede
for
.Ar option
overrides any previous
.Ic append ,
.Ic default ,
.Ic ignore ,
.Ic prepend
or
.Ic supersede
for
.Ar option .
.It Ic uselease Op Ar option , ... ;
Use the unmodified values provided in the lease for
any specified
.Ar option .
.Ic uselease
statements are cumulative.
If no
.Ar option
is specified all lease option values will be used unmodified.
.Ic uselease
for
.Ar option
overrides any previous
.Ic append ,
.Ic default ,
.Ic ignore ,
.Ic prepend
or
.Ic supersede
for
.Ar option .
.El
.Sh OTHER DECLARATIONS
.Bl -tag -width Ds
.It Ic filename Ar path ;
Use
.Ar path
instead of the
.Ic file
field of the DHCP offer when binding a lease.
.It Ic fixed-address Ar ip-address ;
Use
.Ar ip-address
instead of the
.Ic yiaddr
field of the DHCP offer when binding a lease.
.It Ic interface Qo Ar name Qc No { Ar declaration ; ... ; No }
Apply any
.Ar declaration
only to the named interface.
.It Ic reject Ar ip-address ;
Discard leases from the specified address.
If more than one
.Ic reject
is present all leases from any of the
addresses will be discarded.
.It Ic next-server Ar ip-address ;
Use
.Ar ip-address
instead of the
.Ic siaddr
field of the DHCP offer when binding a lease.
.It Ic server-name Ar host ;
Use
.Ar host
instead of the
.Ic sname
field of the DHCP offer when binding a lease.
.El
.Sh SEE ALSO
.Xr dhclient.leases 5 ,
.Xr dhcp-options 5 ,
.Xr dhcpd.conf 5 ,
.Xr dhclient 8 ,
.Xr dhcpd 8