/etc/network/interfaces
A static configuration file used by the old Debian networking system ifupdown
when you boot ifupdown reads this file, runs wpa_supplicant for Wi-Fi authentication, then requests IP via a DHCP client, defaults to using dhclient (from the isc-dhcp-client package). However, it is designed to check for available clients and can use udhcpc or dhcpcd if dhclient is not installed.
Commands
Bring interface up:
ifup <interface>
Bring interface down:
ifdown <interface>
networking.service
The networking service is a systemd unit:
networking.service
It acts as a wrapper that:
- reads
/etc/network/interfaces - brings interfaces down and up
- applies configuration changes
Internally, it runs commands like:
ifdown <interface>
ifup <interface>
What happens when you run it
systemctl restart networking
This effectively does:
- Stops all configured interfaces
- Re-applies
/etc/network/interfaces - Brings interfaces back up with updated settings
When you should use it
Use it after:
- editing
/etc/network/interfaces - changing SSID/password
- modifying interface behavior