184 lines
4.3 KiB
Groff
184 lines
4.3 KiB
Groff
.Dd January 16, 2023
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.Dt DHCLIENT.CONF 5
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.Os
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.Sh NAME
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.Nm dhclient.conf
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.Nd dhcp client configuration
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.Sh SYNOPSIS
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.Nm /etc/dhclient.${mac}.conf
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.Nm /etc/dhclient.${if}.conf
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.Nm /etc/dhclient.conf
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.Sh DESCRIPTION
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.Xr dhclient 8
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configures the network interface according to its
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.Nm
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configuration file, searching for the first file path to exist:
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.Pp
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.Bl -bullet -compact
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.It
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.Pa /etc/dhclient.${mac}.conf
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- where
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.Ar mac
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is the network interface's hardware address.
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(Example:
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.Pa dhclient.00:00:5e:00:53:00.conf )
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.It
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.Pa /etc/dhclient.${if}.conf
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- where
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.Ar if
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is the network interface's name.
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(Example:
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.Pa dhclient.if0.conf )
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.It
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.Pa /etc/dhclient.conf
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- the shared configuration file.
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.El
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.Pp
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Network interface names are not guaranteed to be stable and it's recommended to
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use the hardware address in the file name or in the
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.Sy if
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statement in the shared file.
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.Sh FORMAT
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.Nm
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contains a series of whitespace delimited tokens akin to an
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.Xr ifconfig 8
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invocation.
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The
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.Sq #
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character begins a comment and the rest of the line is ignored.
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If a token names a protocol, then that protocol is selected.
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If a token names a configuration inside the current protocol or a top level
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statement, then that configuration is set to the value of the subsequent
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token.
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.Pp
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Configurations can be generally be set to either a manual value, or
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.Sy auto
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to obtain the value from the DHCP server, or
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.Sy none
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to disable setting the configuration and retain the currently set value.
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If
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.Sy auto
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or
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.Sy none
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follows a protocol name, then all the configurations inside the protocol is set
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to that value.
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.Pp
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The top level statements are:
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.Bl -tag -width "12345678"
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.It Sy if Oo Ar name "|" Sy etherhw: Ns Ar mac "|" Sy id: Ns Ar linkid Oc
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The following configurations only applies to the network interface if it
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matches by its
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.Ar name ,
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its hardware address
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.Ar mac ,
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or its unstable index number
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.Ar linkid .
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The
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.Sy if
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statement can only be used in the shared
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.Pa /etc/dhclient.conf
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file and allows defining a section for each network interface.
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Configurations are applied to all network interfaces until the
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.Sy if
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statement appears.
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.El
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.Pp
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The
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.Sy inet
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protocol contains the following configurations:
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.Bl -tag -width "12345678"
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.It Sy address Oo Ar ip "|" Sy auto "|" Sy none Oc
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The local address in
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.Xr inet 4
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address notation.
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(Default:
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.Sy auto )
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.It Sy router Oo Ar ip "|" Sy auto "|" Sy none Oc
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The default route in
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.Xr inet 4
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address notation.
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(Default:
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.Sy auto )
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.It Sy subnet Oo Ar ip "|" Sy auto "|" Sy none Oc
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The subnet mask in
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.Xr inet 4
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address notation.
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(Default:
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.Sy auto )
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.El
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.Pp
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The
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.Sy dns
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protocol contains the following configurations:
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.Bl -tag -width "12345678"
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.It Sy servers Oo Ar ip1,ip2,... "|" Sy auto "|" Sy none Oc
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The comma separated list of DNS servers in
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.Xr inet 4
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address notation.
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A singular comma means the empty list.
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(Default:
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.Sy auto )
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.El
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.Pp
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The
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.Sy ether
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protocol contains the following configurations:
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.Bl -tag -width "12345678"
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.It Sy address Oo Ar mac "|" Sy auto "|" Sy none Oc
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The local address in
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.Xr ether 4
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address notation.
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.Sy auto
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sets it to the hardware address.
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(Default:
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.Sy auto )
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.El
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.Sh EXAMPLES
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.Ss Manually configuring an interface
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To fully manually configure the network interface
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.Pa if0 ,
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even if the network interface's device name changes over time, first first look
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up its ethernet hardware address:
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.Bd -literal -offset indent
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$ ifconfig -l if0 ether hwaddress
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00:00:5e:00:53:00
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.Ed
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.Pp
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Then write an
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.Pa /etc/dhclient.conf
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section using the
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.Sy if
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statement:
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.Bd -literal -offset indent
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if etherhw:00:00:5e:00:53:00
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inet address 192.0.2.4 router 192.0.2.1 subnet 255.255.255.0
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dns servers 192.0.2.2 192.0.2.3
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.Ed
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.Ss Obtaining the DNS servers on only one interface
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The DNS server list is global and a system with multiple network interfaces can
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obtain the list on only the preferred interface by disabling DNS configuration
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and enabling it on the desired interface:
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.Bd -literal -offset indent
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dns none
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if etherhw:00:00:5e:00:53:00
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dns auto
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.Ed
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.Ss Disabling dhclient
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.Xr dhclient 8
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can be disabled on an interface by disabling configuration of the inet and dns
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protocols:
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.Bd -literal -offset indent
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inet none
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dns none
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.Ed
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.Sh SEE ALSO
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.Xr ether 4 ,
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.Xr if 4 ,
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.Xr inet 4 ,
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.Xr dhclient 8 ,
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.Xr dnsconfig 8 ,
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.Xr ifconfig 8
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.Sh CAVEATS
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The list of DNS servers is global and should only be obtained on one network
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interface to avoid interference.
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