Sstrhsrtj

On my machine I have multiple interfaces which often have a dhcp server running. I now want to react differently on various 'setups':

• when there is wifi, use wifi


• when there is ethernet, use ethernet (I have an extra profile there, too)


• when there is both, use one of them (or both, or whatever.. just work)


• when interface usb0 or usb1 occur, only enable dhcp on them when someone issues dhcpcd <interface>
  

My current dhcpcd.conf looks like

# See dhcpcd.conf(5) for details.



# Allow users of this group to interact with dhcpcd via the control socket.

#controlgroup wheel



# Inform the DHCP server of our hostname for DDNS.

hostname



# Use the hardware address of the interface for the Client ID.

#clientid

# or

# Use the same DUID + IAID as set in DHCPv6 for DHCPv4 ClientID as per RFC4361.

# Some non-RFC compliant DHCP servers do not reply with this set.

# In this case, comment out duid and enable clientid above.

duid



# Persist interface configuration when dhcpcd exits.

persistent



# Rapid commit support.

# Safe to enable by default because it requires the equivalent option set

# on the server to actually work.

option rapid_commit



# A list of options to request from the DHCP server.

option domain_name_servers, domain_name, domain_search, host_name

option classless_static_routes

# Most distributions have NTP support.

option ntp_servers

# Respect the network MTU. This is applied to DHCP routes.

option interface_mtu



# A ServerID is required by RFC2131.

require dhcp_server_identifier



# Generate Stable Private IPv6 Addresses instead of hardware based ones

slaac private





interface eth0

arping 192.168.1.77



profile 192.168.1.77

static ip_address=192.168.1.65

static routers=192.168.1.77

static domain_name_servers=192.168.1.77





interface usb0

nogateway



interface usb1

nogateway

The wifi/ethernet part seems to work, though I haven't tested it thoroughly. But I don't know, how to set up my usb interfaces to only respond to DHCP on command. The nogateway is just there to prevent usb interfaces to screw up my default routes ATM.

How do I need to configure dhcpcd?

Edit 1:
I am on a Gentoo system with no more network configuration except my wpa_supplicant.conf

If you are running a Debian based distro just look at the last lines of /etc/default/isc-dhcp-server:

# On what interfaces should the DHCP server (dhcpd) serve DHCP requests?

#       Separate multiple interfaces with spaces, e.g. "eth0 eth1".

INTERFACES="eth1"