My Ubuntu 12.04 VirtualBox (Windows 7 host) suddenly stopped connecting to remote servers unless I refer to them by their IP addresses.

I'm looking for a way to fix this problem (or at least to troubleshoot it).

NOTE: Neither restarting the VB nor restarting the host machine fixed the problem.

IMPORTANT: The VB has been operating flawlessly since it was set up several months ago. Furthermore, I did not make any changes to the configurations, settings, etc. of either the guest or the host machine in the last several days. (AFAICT, the loss of DNS just happened out-of-the-blue.) Since the configurations of the guest and host machines have been so successful until now, in general I want to stay clear of solutions that would involve changing them. (Of course, this does not apply to configuration files that get modified frequently by automated process, such as resolv.conf, since it is not unusual for such a file to become corrupted during normal operation.)


My /etc/network/interfaces file consists of only the following two lines:

auto lo
iface lo inet loopback

Furthermore, my /etc/resolv.conf file (which is not a symlink to ../run/resolvconf/resolv.conf) has one search line, showing my workplace's network's domain, followed by two nameserver lines; the hosts corresponding to the IP addresses mentioned in these two lines are both up, according to ping.

Just to be clear, I did not create or edit either of these files.

% ifconfig -a
eth0      Link encap:Ethernet  HWaddr 61:39:ba:21:c7:cc  
          inet addr:  Bcast:  Mask:
          inet6 addr: 2fd1::f92:2c24:7735:e9ac/64 Scope:Link
          RX packets:946 errors:0 dropped:0 overruns:0 frame:0
          TX packets:995 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:122625 (122.6 KB)  TX bytes:96928 (96.9 KB)

lo        Link encap:Local Loopback  
          inet addr:  Mask:
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:10 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:1380 (1.3 KB)  TX bytes:1380 (1.3 KB)

OK, I found a solution here which is to run

sudo dpkg-reconfigure resolvconf

In the interaction with dpkg-reconfigure, I answered YES to the first question and NO to the second one. This bug report may be relevant to the problem I had.

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