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I upgraded a Ubuntu Zesty to Artufl over SSH using upgrade-manager. All went well except for DNS. Name resolution fails, including ping. I still have an IP and I can SSH into it after reboot, but that may be old lease information. I understand systemd now handles resolver duties.

The tail of my dmeg is showing failed DHCP audits.

[    8.397015] audit: type=1400 audit(1515252083.757:46): apparmor="DENIED" operation="open" profile="/usr/lib/NetworkManager/nm-dhcp-helper" name="/usr/local/lib/libz.so.1.2.11" pid=951 comm="nm-dhcp-helper" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
[    8.434243] audit: type=1400 audit(1515252083.794:47): apparmor="DENIED" operation="open" profile="/usr/lib/NetworkManager/nm-dhcp-helper" name="/usr/local/lib/libz.so.1.2.11" pid=955 comm="nm-dhcp-helper" requested_mask="r" denied_mask="r" fsuid=0 ouid=0

/etc/systemd/resolved.conf has the following. I don't have other Ubuntu machines so I am not sure if this is expected under systemd.

[Resolve]
#DNS=
#FallbackDNS=
#Domains=
#LLMNR=yes
#MulticastDNS=yes
#DNSSEC=no
#Cache=yes
#DNSStubListener=udp

Searching for the AppArmor failure is returning 0 hits. I suspect that has a lot to do with the troubles, and I was surprised Google returned 0 results.

There are no apparmor-profile.dhclient files in /usr or /etc as discussed at Ubuntu Issue 1417658, so it is a dead end. I also tried uncommenting #DNS= and setting it to DNS=yes in resolved.conf but that did not fix the issue.

What is the problem and how do I fix it?


Comment] What is the output of ls -l /etc/resolv.conf

$ ls -l /etc/resolv.conf
lrwxrwxrwx 1 root root 29 Nov 29  2016 /etc/resolv.conf -> ../run/resolvconf/resolv.conf

Here are some Ubuntu bug reports for the problems:

  • What is the output of ls -l /etc/resolv.conf? – GAD3R Jan 6 '18 at 15:56
  • 1
    ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf – GAD3R Jan 6 '18 at 16:04
  • Thanks @GAD3R. That did not help. I'm going to install Fedora 27. That should fix the problem once and for all. It is kind of surreal... five years ago most of my Linux machines were Ubuntu. I don't think I have any Ubuntu machines left because of problems like this. – user56041 Jan 7 '18 at 1:01

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