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I have a question about why my DNS settings got messed up. I've fixed the issue (I think), but I'm curious as to why it happened. My Linux Mint 18.3 laptop had been working flawlessly. I recently installed PulseSecure to VPN into my university's secure network from off campus. That worked great for several days. Then all of a sudden, my internet stopped working at home. The wireless was connected, but it could never resolve a host. After some Googling (from another computer), I figured out that I could ping my gateway, some IP addresses, and Google DNS 8.8.8.8., but not website names.

I followed some internet advice and checked my resolv.conf file and saw

~ $ cat /etc/resolv.conf
search colostate.edu
nameserver 129.82.103.91
nameserver 129.82.103.79

Those are CSU internal IP addresses. I added two lines to my resolv.conf

nameserver 8.8.8.8
nameserver 8.8.4.4

Then, to make sure the changes stuck, I opened my network connections for my home internet, went to the IPv4 Settings, changed Method to Automatic DHC addresses only, and set DNS server to 8.8.8.8 (again per internet advice I found). Things are working fine now, for the moment, although they feel a bit sluggish.

I noticed that, when I logged in to my VPN via pulse secure just now, resolv.conf is back to its original form

search colostate.edu
nameserver 129.82.103.91
nameserver 129.82.103.79

like it was just overwritten. I'm concerned that my internet now will no longer work and I'll have to fix this every time.

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There is a known issue of interactions between using some VPN software solutions and resolvconf.

resolvconf turns /etc/resolv.conf into a symbolic link and is using another location to resolve DNS under /run/resolvconf/resolv.conf.

In your case, the VPN deletes and replaces /etc/resolv.conf, without taking on consideration the current setup. Such symbolic link has to be restored each time after you use the VPN, or as an alternative, delete the package resolvconf as a temporary measure.

I would file a bug with the VPN software maker too.

  • So I was just logged in to my VPN, and I checked resolv.conf to look and see if had been overwritten. Now it says 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 nameserver 127.0.1.1. How do I restore resolve.conf? For what its worth, it runs a lot faster now. – Nate May 4 '18 at 2:08
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    See man resolvconf. Basically your system has an utility script that collects and keeps the DNS settings from various sources (static settings, DHCP, active VPN connections) and selects the most appropriate settings whenever you activate/deactivate network connections or VPNs. It looks like your PulseSecure VPN skips this mechanism and instead rewrites /etc/resolv.conf directly. That's not ideal: it should be submitting its DNS settings to the resolvconf script instead, and only the resolvconf script should be modifying the actual /etc/resolv.conf file. – telcoM May 4 '18 at 4:55

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