Wpa supplicant/Setup for dhcpcd as network manager

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