46

I have an Ubuntu 16.04 system with two interfaces - eth0 configured with DHCP and eth1 configured with static ip addresses.

The /etc/network/interfaces file has the following config

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp

# The Secondary network interface
auto eth1
iface eth1 inet static
address 10.10.1.10
netmask 255.255.255.0
dns-nameservers 74.82.42.42 4.2.2.2

## Virtual Interfaces for virtual hosts
auto eth1:11
iface eth1:11 inet static
address 10.10.1.11
netmask 255.255.255.0

auto eth1:12
iface eth1:12 inet static
address 10.10.1.12
netmask 255.255.255.0

auto eth1:13
iface eth1:13 inet static
address 10.10.1.13
netmask 255.255.255.0

The issue is, when DHCP server is not available on eth0 link or if the eth0 link is down, the system hangs for 5 mins, significantly slowing down the boot process.

violet@ubuntu-xenial:~$ systemd-analyze blame
      5min 241ms networking.service
          1.529s nmbd.service
          1.524s winbind.service

I tried reducing the time in /etc/systemd/system/network-online.target.wants/networking.service file which makes the system boot faster without waiting for the network service, however, that fails to load the virtual interfaces on eth1.

Is there a cleaner way to let the system boot without full network configuration on eth0 interface and still load all the static network configuration on eth1?

j202
  • 561

3 Answers3

57

It seems someone was paranoid about a client not getting it's DHCP in time.

Edit this file /etc/dhcp/dhclient.conf and set timeout to a reasonable value, like

timeout 15

The default value of 300 seconds is way too high. The suggested replacement value of 15 was tested and works fine.

delfiler
  • 237
boutch55555
  • 1,226
29

So in your /etc/network/interfaces, change this:

# The primary network interface
auto eth0
iface eth0 inet dhcp

to this:

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp

This will start interface eth0 when the kernel detects a hotplug event from the interface (i.e. when you plug a cable in), instead of starting it at boot.

guntbert
  • 13,475
Jonathan Walter
  • 391
3

As referenced in you can change the timeout value for raising the network interface (if running systemd):

Open a terminal window, and enter the command:

sudo nano /etc/systemd/system/network-online.target.wants/networking.service

Then change the line TimeoutStartSec=5min to a value that you choose. Save the file by pressing Ctrl+o and then Ctrl+x.

Finally, restart the daemon:

sudo systemctl daemon-reload
Ken Sharp
  • 1,086
Mike
  • 31