Home / ubuntu / Questions / 4901
Accepted
Dmitriy Likhten
Asked: 2010-09-30 06:35:45 +0800 CST

Network not starting up on boot

  • 772

Basically my network won't start. Can't use wired connections.

To make it a further brain-scratcher, when booting into recovery, and using the network console, the network comes up and works. Outside of recovery nothing.

As far as I can tell no settings changed between powering off and on since last time it worked, except for an automatic kernel upgrade. Using an older kernel does not seem to help.

Also this hardware configuration worked perfectly fine for over a year with kernel upgrades and all. Network was always automatic.

Information for follow up questions...

Network manager is running.

Strangely enough, my network interface was never started, nor was DHCP. Where in the configuration can I find this?

To manually resolve the problem:

sudo ifconfig eth0 up
sudo /etc/dhclient

What could have happened in my config to not make this work automatically.

Info gathered:

> lspci | grep net
> 6:00:19.0 Ethernet controller: Intel Corporation 82566DM-2 Gigabit Network Connection (rev 02)

Contents of /etc/network/interfaces

auto lo
iface lo inet loopback

After adding 

auto eth0
iface eth0 inet dhcp

the eth0 interface comes up, but the dhclient does not.

--

The problem re-occurred when waking up from sleep.

networking

4 Answers

  1. Best Answer

    You are likely missing the line for this in the interfaces file. Open /etc/network/interfaces and check if there is a line for eth0 If not add the following:

    auto eth0
iface eth0 inet dhcp

    This will add the eth0 interface - and use DHCP on boot and wakeup.

    If you're still not getting DHCP response you may also need to add dhcp back into defaults:

    sudo update-rc.d dhcp3-server defaults

    • 15

  2. What does ifconfig -a show when it's not working? Is there an eth0? If it's not, I'd check the modules blacklists /etc/modprobe.d/blacklist*. I would have expected the recovery console to honour these though so moving on...

    If you do have an interface, it could be some dodgy config inside network-manager. Recovery mode just uses some defaults IIRC so I'd open up the network settings (right click the applet, click edit connections) and check a few things:

    • Connect Automatically is checked
    • You have a MAC address
    • MTU is automatic
    • 802.1x security is disabled
    • IPv4 is set to Automatic (DHCP)
    • Require IPv4 is checked
    • There should be no special routes
    • IPv6 is set to ignore

    If ifconfig -a isn't showing an eth0 device, it could be something bizarrely hardware specific. What does lspci | grep net show? If nothing, do you know what the network chipset is?

    • 1

  3. Could pm-powersave be the cause of your problem? My answer to How to connect wirelessly in a cafe with 11.04 might apply

    • 0

  4. I've installed dhcpcd5 and it worked for me.

    sudo apt-get install dhcpcd5

    • -2