Network management using DHCPCD

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This article is based on a posting in the Gentoo Forums and explains how to use dhcpcd for complete network stack management.

Of course, it's possible to use dhcpcd together with net.* scripts. In fact, if dhcpcd is installed, it's used as the default DHCP client if config_eth0="dhcp" is set in /etc/conf.d/net. This article is specifically about using dhcpcd standalone.

Setup

Make sure dhcpcd is installed. Next, add it to the default runlevel and start the service.

If using OpenRC, do:

root #rc-update add dhcpcd default
root #rc-service dhcpcd start

Or, if using systemd:

root #systemctl enable dhcpcd
root #systemctl start dhcpcd

This setup deviates from the default networking instructions in the Gentoo Handbook. It has the advantage that it provides automatic switching between wired and wireless network interfaces.

Wireless

wpa_supplicant

wpa_supplicant can be used for authentication of wireless and wired network interfaces. Create the configuration file if it does not exist:

FILE /etc/wpa_supplicant/wpa_supplicant.conf
# Allow users in the 'wheel' group to control wpa_supplicant
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=wheel

# Make this file writable for wpa_gui / wpa_cli
update_config=1

For authentication for the wired interface, add the configuration file mentioned in Wpa_supplicant#Setup_wired_802.1X.

First follow the setup guide for dhcpcd.

Emerge wpa_supplicant (Version >=2.6-r2 is needed in order to get the CONFIG_MATCH_IFACE option added in April 2017):

root #emerge --ask net-wireless/wpa_supplicant

Using OpenRC

Complete its conf.d file with the -M option for the wireless network interface:

FILE /etc/conf.d/wpa_supplicant
wpa_supplicant_args="-B -M -c /etc/wpa_supplicant/wpa_supplicant.conf"

In case authentication for the wired interface is needed, this configuration file should look like:

FILE /etc/conf.d/wpa_supplicant
wpa_supplicant_args="-ieth0 -Dwired -c/etc/wpa_supplicant/wpa_supplicant_wired.conf -B -M -c/etc/wpa_supplicant/wpa_supplicant.conf"

With the configuration done, run it as a service:

root #rc-update add wpa_supplicant default
root #rc-service wpa_supplicant start

Using Systemd

Systemd allows a simpler per-device setup without needing to create the above conf.d files. As explained under wpa_supplicant item in the Native services section, a service symlink such as wpa_supplicant@wlan0.service looks for a separate configuration file to manage the device wlan0 in this case.

To configure a specific device this way, first copy or rename the /etc/wpa_supplicant/wpa_supplicant.conf file as /etc/wpa_supplicant/wpa_supplicant-DEVNAME.conf where DEVNAME should be the name of the device, such as wlan0.

Then, navigate to /etc/systemd/system/multi-user.target.wants and create the symlink:

root #ln -s /lib/systemd/system/wpa_supplicant@.service wpa_supplicant@DEVNAME.service

where DEVNAME is same device name as in the conf file above.

Important
Note the @ signs on both arguments in the symlink step.

Test the system:

root #systemctl daemon-reload
root #systemctl start wpa_supplicant@DEVNAME
root #systemctl status wpa_supplicant@DEVNAME

Using net-wireless/iwd

See the iwd article.

Testing

Stop the dhcpcd service, then start dhcpcd with the -d (--debug) and -B (--nobackground) options enabled to see it starting the connection:

root #rc-service etc/init.d/dhcpcd stop
root #dhcpcd -dB 
dhcpcd-6.11.3 starting
dev: loaded udev
eth0: executing `/lib/dhcpcd/dhcpcd-run-hooks' PREINIT
eth0: executing `/lib/dhcpcd/dhcpcd-run-hooks' NOCARRIER
wlan0: executing `/lib/dhcpcd/dhcpcd-run-hooks' PREINIT
wlan0: executing `/lib/dhcpcd/dhcpcd-run-hooks' CARRIER
DUID xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
wlan0: IAID XX:XX:XX:XX
wlan0: delaying IPv6 router solicitation for 0.9 seconds
wlan0: delaying IPv4 for 0.3 seconds
eth0: waiting for carrier
wlan0: reading lease `/var/lib/dhcpcd/dhcpcd-wlan0-.lease'
wlan0: rebinding lease of 192.168.178.23
wlan0: sending REQUEST (xid 0x66820be2), next in 3.3 seconds
wlan0: acknowledged 192.168.178.23 from 192.168.178.1
wlan0: leased 192.168.178.23 for 864000 seconds
wlan0: renew in 432000 seconds, rebind in 756000 seconds
wlan0: writing lease `/var/lib/dhcpcd/dhcpcd-wlan0-.lease'
wlan0: IP address 192.168.178.23/24 already exists
wlan0: changing route to 192.168.178.0/24
wlan0: changing default route via 192.168.178.1
wlan0: ARP announcing 192.168.178.23 (1 of 2), next in 2.0 seconds
wlan0: executing `/lib/dhcpcd/dhcpcd-run-hooks' BOUND
wlan0: soliciting an IPv6 router
wlan0: sending Router Solicitation
wlan0: ARP announcing 192.168.178.23 (2 of 2)

Static IP address

In case the network interface card should be configured with a static IP address, type it into the graphical user interface. Without the graphical user interface, entries can also be manually added (currently offline) to /etc/dhcpcd.conf as described in Dhcpcd#Static_IP_addresses.

Migration from Gentoo net.* scripts

When migrating from Gentoo's net.* scripts it is essential to remove the net.* scripts from the runlevels. To see what runlevels they are currently in:

user $rc-config list | grep 'wpa_supplicant\|dhcpcd\|net\.'
  net.wlp8s0                default
  dhcpcd                    default

Any match starting with net. must not have a runlevel assigned. In the above example, net.wlp8s0 needs to be removed:

root #rc-update del net.wlp8s0
root #rc-service net.wlp8s0 stop

Once the network setup works well, it is possible to completely remove the old Gentoo net.* scripts. To do so, disable the netifrc USE flag, re-emerge sys-apps/openrc and finally unmerge net-misc/netifrc:

root #echo 'sys-apps/openrc -netifrc' >> /etc/portage/package.use
root #emerge --ask --newuse --oneshot sys-apps/openrc
root #emerge --ask --verbose --depclean net-misc/netifrc

Also the old configuration files and symlinks can be removed:

root #rm /etc/conf.d/net
root #rm /etc/init.d/net.*

Network dependent services

Manipulating network dependent services by dhcpcd is no longer supported since openrc-0.16.4.

Graphical User interface

A dhcpcd graphical user interface is provided by net-misc/dhcpcd-ui.

See also

  • Dhcpcd — a popular DHCP client capable of handling both IPv4 and IPv6 configuration.
  • Dhcpcd-ui — a Qt and GTK monitor and configuration graphical user interface for dhcpcd.

External resources

Retrieved from "https://wiki.gentoo.org/index.php?title=Network_management_using_DHCPCD/en&oldid=1216074"