This is the /etc/network/interfaces file from my vbox debian 9.0 system.
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
source /etc/network/interfaces.d/*
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
allow-hotplug enp3s0
iface enp3s0 inet static
address 192.168.1.160
netmask 255.255.255.0
gateway 192.168.1.1
The problem is when the system boots up, it will not config the network interface:
$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether 08:00:27:e2:06:48 brd ff:ff:ff:ff:ff:ff
To use the network, I have to su to root and run dhclient, and then everything is fine:
$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:e2:06:48 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.160/24 brd 255.255.255.255 scope global enp0s3
valid_lft forever preferred_lft forever
inet6 fe80::a00
fee2:648/64 scope link
valid_lft forever preferred_lft forever
Also:
# ifup enp0s3
ifup: unknown interface enp0s3