How to get my eth0 up and running? I have tried all but none bring this up

Question

Ubuntu 11.04. Why the eth0 gets down, is there no tools or script to bring it up?

I tried several way, but none worked. Any idea?

1) vim /etc/network/interfaces

auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp

2) ifup eth0

a)

ssh stop/waiting
ssh start/running, process 1723

b) ifup eth0

ifup: interface eth0 already configured

3) restarted networkmanager but same no luck

Follow up:

1) sudo update-rc.d -f NetworkManager remove
2) sudo apt-get install dhcpcd
3) dhcpcd eth0
4) ifup eth0

Solution

What do you mean, "when it gets down"?

NetworkManager and /etc/network/interfaces are two separate ways of controlling the network, you should use one or the other. If you use NetworkManager, the interfaces file should be empty (everything commented out for eth0).

ifconfig -a output may help. Can you ping your default gateway? Or anything at all?

Comments

[Admin]

I can not ping anything at-all. And my total interface lights goes down when Ubuntu starts.

[Admin]

Now, after login with LiveCD, i do not have Eth0 up either.

[Caesium]

You should consolidate as much relevant information as possible into the original question, including this. Post hardware details, output of appropriate parts of dmesg (grep for eth0, perhaps).

[Admin]

sudo dmesg | grep eth0; is showing eth0: link becomes ready

[Admin]

Do i have to install "apt-get install dhcpcd"? What does that do.