Debian: No internet connection on reboot

Question

A server I develop on ran out of memory during an overnight job and had to be rebooted. Upon reboot, it no longer has an internet connection. I've exhausted my google-fu abilities trying to troubleshoot, so now I have come to you.

More Info:

ifconfig eth0

    eth0      Link encap:Ethernet  HWaddr 00:1a:a0:cb:ec:a8
              BROADCAST MULTICAST  MTU:1500  Metric:1
              RX packets:0 errors:0 dropped:0 overruns:0 frame:0
              TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:1000
              RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
              Interrupt:16

/etc/network/interfaces

auto lo
iface lo inet loopback

auth eth0
iface eth0 inet dhcp

Any ideas?

Answer 1

You appear to have mis-spelled auto:

auth eth0

Should be

auto eth0

Classic muscle memory issue. I've made this particular mistake a few times. :)

Answer 2

Assuming the system should be using DHCP:

See if dhclient or dhcpd is running:

ps aux | grep dhclient
ps aux | grep dhcpd

If they aren't, figure out which is installed (you can do this by just trying to tab-autocomplete them. Then do:

sudo dhclient eth0

or

sudo dhcpd eth0

If it is already running, try to kill it and run it again (so you can see debug messages).

What does "dmesg" output (post only the part regarding eth0)?

If none of this works, try doing

sudo ifconfig eth0 down
sudo ifconfig eth0 up

And then try the above commands again.

If you supply more information, I can help you further.