Ubuntu – Need to enter a dhclient at every restart at Ubuntu

Ubuntu

my internet was working just fine until one certain day. From this day until today every time I restart the pc I have to execute a dhclient to make internet connection work again.
I searched old threads and found this: Have to dhclient each restart to access internet
Unfortunatelly none of the proposed solutions worked for me. Here my /etc/network/interface it is:

auto lo

iface lo inet loopback

I changed the two lo to eth0 and didn't work. Then I looked at the /var/lib/dhcp3/dhclient.leases and there exists a line

interface "eth0"

so following the link tip, changing the internet interface of /etc/network/interface to the same value of /var/lib/dhcp3/dhclient.leases should work, but it didn't for me.
Also putting dhclient at the /etc/rc.local didn't work.

So, any tips?

Sorry to open this question. The mistake was mine, the last line was

iface lo inet loopback

and I changed it to

iface eth0 inet loopback

instead of changing it to

iface eth0 inet dhcp

Anyway, how was possible that this file was changed (I am assuming that before it was

iface eth0 inet dhcp

to this loopback interface? What could possible happen to provoke that?

Best Answer

You should not change the entries in /etc/network/interfaces that refer to the lo interface.

Your entries for eth0 should look like this:

auto eth0
iface eth0 inet dhcp

For a detailed howto see: http://www.cyberciti.biz/faq/setting-up-an-network-interfaces-file/

Also this question on superuser: https://superuser.com/questions/151936/how-to-automate-running-the-dhclient-in-ubuntu

Related Solutions

Ubuntu – dhcp server ‘not configured to listen on any interfaces’

OK, I think i've fixed this issue. And it IS a bug in Linux's network manager.

See, the network manager runs as part of the boot process (that'd be the 'S50NetworkManager' symlink) and brings up your ethernet interfaces. However, it does it asynchronously. This means that the network manager returns immediately, implying to the scripts after it, "OK - network's been set up." Actually, it hasn't, and the network manager is sitting there in the background getting on with setting up the network. Meanwhile, the boot scripts after it are running with the assumption that the network interfaces will be available, which is a race condition, depending on whether the network manager has gotten round to setting them up yet.

This is a horrible situation and a bug I'm amazed hasn't been fixed. One way of getting round it is to ditch the network manager and instead set up your interfaces by editing /etc/network/interfaces. Rather than do that work, though, I tried the ugly hack suggested in this bug report: https://bugzilla.redhat.com/show_bug.cgi?id=486372

I added a 5 second delay ('sleep 5') into the beginning of the start function in dhcp3-server's init.d script, this giving the network manager ample time to get the network interfaces set up (although of course there is still no guarantee) - and it worked. Now, dhcpd succeeds on startup.

As detailed in bugs #486372 and #447442 on bugzilla.redhat.com, this is either a bug with network manager (it should block until its wired network interfaces are available), or with dhcpd (it should be updated to wait for network interfaces to become available, rather than just crashing out). It is definitely a bug of sorts, though.

Ubuntu – Setting up a static IP address (public) in Ubuntu

You are missing a default route.

In ubuntu, you'll need:

 gateway <IP of default route>

Here is /etc/network/interfaces on my system (with a private IP, but there is no difference):

auto eth0
iface eth0 inet static
    address 10.22.16.2
    netmask 255.255.255.0
    network 10.22.16.0
    broadcast 10.22.16.255
    gateway 10.22.16.1
    # dns-* options are implemented by the resolvconf package, if installed
    dns-nameservers 10.21.1.21
    dns-search example.com

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