Lost DNS in upgrade to Precise

[arist]

Today I did the network upgrade from 11.10 to 12.04 on my desktop computer. Everything seemed to go well, but after restarting I was unable to access the Internet. Pinging a domain name returns "unknown host". I can ping IP addresses, however. I went into System Settings>Network Connections and made sure that the address for the DNS server is the same as on my netbook (which is still running Oneiric). I tried replacing /etc/NetworkManager/NetworkManager.conf with the old (Oneiric) version, then went back. After every change I did a restart. No luck. I'm sure there's a simple solution for this. What is it?

[SteveRiley]

One of the changes that Precise brings is the introduction of dnsmasq, configured as a local DNS cache. I've experimented with various ways of removing this, but the result always feels brittle. Ultimately, I ended up commenting out one line -- shown in bold -- in /etc/NetworkManager/NetworkManager.conf:


steve@x1:~$ cat /etc/NetworkManager/NetworkManager.conf

[main]
plugins=ifupdown,keyfile
# dns=dnsmasq

no-auto-default=F0:DE:F1:A5:AA:41,

[ifupdown]
managed=false

Now, when I examine /etc/resolv.conf, I can see the DNS servers that I've configured my DHCP server (actually, my router) to supply:


steve@x1:~$ cat /etc/resolv.conf
nameserver 4.2.2.1
nameserver 4.2.2.2
search local

[arist]

Ultimately, I ended up commenting out one line -- shown in bold -- in /etc/NetworkManager/NetworkManager.conf:


steve@x1:~$ cat /etc/NetworkManager/NetworkManager.conf

[main]
plugins=ifupdown,keyfile
# dns=dnsmasq


Yes, that's the very first thing I did, commenting out that line. Made no difference.


Now, when I examine /etc/resolv.conf, I can see the DNS servers that I've configured my DHCP server (actually, my router) to supply:


steve@x1:~$ cat /etc/resolv.conf
nameserver 4.2.2.1
nameserver 4.2.2.2
search local

Funny, my resolv.conf file has no nameservers in it. It looks like this:

#Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN.
Invoking resolvconf -u does nothing. I tried editing the file by hand, basically copying the one from the netbook, and after rebooting it is indeed overwritten, going back to the above. There must be a way to get my nameserver into resolv.conf.

[SteveRiley]

I'll take another look tomorrow. Seem to recall another step, but will need to check bash history first.

[arist]

Following these instructions, http://manpages.ubuntu.com/manpages/precise/man8/resolvconf.8.html, I added a "dns-nameservers" line to /etc/network/interfaces, and now the nameservers show up in resolv.conf, and I have Internet again.

[GreyGeek]

My /etc/resolv.conf has the following:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.0.1
search earthlink.net


And my internet connection works fine against both the wireless and the eth0 connections.

Also, I added my ISP domain and DNS addresses in my TL-WR1043N wireless router.

[Snowhog]

My /etc/resolv.conf contains:

# Generated by NetworkManager
nameserver 127.0.0.1

Wired and wireless work without any issues what so ever.

My /etc/NetworkManager/NetworkManager.conf contains:



[main]
plugins=ifupdown,keyfile
dns=dnsmasq


no-auto-default=98:4B:E1:C4:95:02,


[ifupdown]
managed=false

[SteveRiley]

Following these instructions, http://manpages.ubuntu.com/manpages/precise/man8/resolvconf.8.html, I added a "dns-nameservers" line to /etc/network/interfaces, and now the nameservers show up in resolv.conf, and I have Internet again.
Are you using static IP addresses defined in /etc/network/interfaces?


My /etc/resolv.conf contains:
---
My /etc/NetworkManager/NetworkManager.conf contains:
Those are the expected configuration files when DHCP assigns IP addresses and you haven't made any changes to dnsmasq.

[Snowhog]

Those are the expected configuration files when DHCP assigns IP addresses and you haven't made any changes to dnsmasq.
Which is my case. I too, was thinking that arist might be using a static IP.

[arist]

Are you using static IP addresses defined in /etc/network/interfaces?

Those are the expected configuration files when DHCP assigns IP addresses and you haven't made any changes to dnsmasq.

That's right, I'm using static IPs for my computers, so I can network them using NFS. That undoubtedly complicates things, but it hadn't occurred to me that whether I was using DHCP or not would affect DNS. Before Precise it had never been necessary to do anything with /etc/network/interfaces in order to get DNS to work with static IPs. I haven't made changes to dnsmasq: NetworkManager.conf is the default version.

Curious that Snowhog's resolv.conf is generated by NetworkManager, while GreyGeek's and mine are generated by resolvconf. Would that be because we use static IPs?