DNS issues - unable to ping domain names
by jackwayneright from LinuxQuestions.org on (#6HH8K)
Hello! I'm attempting to debug what I think is a DNS issue with a server, and I'm unsure how to proceed.
Main information
The server can `ping 8.8.8.8`, but cannot `ping google.com` (`Name or service not known`). My `/etc/resolv.conf` contains:
Code:# 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
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.
nameserver 8.8.8.8
nameserver 127.0.0.53
options edns0This is the contents when it is regenerated using `resolvconf -u`.
Previously when I had manually added `nameserver 8.8.8.8` to the top of `/etc/resolv.conf`, I was able to `ping google.com`, but other services (see long version) still seemed to be failing in some way. However, since I've attempted some other fixes, such as `sudo apt install --reinstall resolvconf network-manager libnss-resolve` and others, even the presence of `nameserver 8.8.8.8` in `/etc/resolv.conf` does not seem to allow `ping google.com` to work. I'm also now unsure of where `nameserver 8.8.8.8` is being added from during a `resolvconf -u`, as none of `/etc/systemd/resolved.conf`, `/etc/resolvconf/resolv.conf.d/head`, or `/etc/resolvconf/resolv.conf.d/base` seem to contain this entry, and `/etc/network/interfaces.d/` is empty.
My `systemd-resolve --status` appears as:
Code:Global
DNS Servers: 8.8.8.8
8.8.4.4
DNSSEC NTA: 10.in-addr.arpa
16.172.in-addr.arpa
168.192.in-addr.arpa
17.172.in-addr.arpa
18.172.in-addr.arpa
19.172.in-addr.arpa
20.172.in-addr.arpa
21.172.in-addr.arpa
22.172.in-addr.arpa
23.172.in-addr.arpa
24.172.in-addr.arpa
25.172.in-addr.arpa
26.172.in-addr.arpa
27.172.in-addr.arpa
28.172.in-addr.arpa
29.172.in-addr.arpa
30.172.in-addr.arpa
31.172.in-addr.arpa
corp
d.f.ip6.arpa
home
internal
intranet
lan
local
private
test
Link 11 (veth399f989)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 9 (vethc76fcf1)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 7 (vethbb5aff2)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 5 (br-ad7981a8fd08)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 4 (docker0)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 3 (eno2)
Current Scopes: DNS
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
DNS Servers: 134.74.128.7
134.74.192.2
DNS Domain: ~.
Link 2 (eno1)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: noAdditional information
I originally set up this server for my PhD advisor when I was student 5 or so years ago. Primarily, they use this server to host a WordPress site and a MediaWiki site that I set up at the time. This has continued to work fine for the last 5 years.
The original sign of some issue was that, recently, for both the WordPress site and the MediaWiki site, any page updates began to fail. For example, the MediaWiki pages can still be viewed, but upon attempting to submit an edit to a page, the user receives a timeout. On the server, Nginx receives the POST, PHP seems to execute the appropriate script for the post, but then the page is left un-updated. I'm not finding any errors in any of the Nginx, PHP, or database logs. Given that there are the other DNS issues made obvious from the above pinging, I suspect that the server is sending requests to itself, but due to these DNS issues, these requests are never really sent or received.
The server is behind a university controlled entry point, then a lab router. I no longer have physical access to the machine, but I can periodically have someone go in to physically access the machine when needed. As part of my attempts to fix it, at one point I had run a package update followed by a reboot. For one reason or another, the reboot did not complete, and the machine only shutdown. Someone had to be sent in physically to turn the machine back on for me. So with my other fixes, I would hope to avoid trying solutions that require reboots, though, I understand this often may be required.
I am far from an expert in either unix related topics or networking topics, so I apologize in advance for any obvious mistakes or troubleshooting that I haven't checked.
Any suggestions would be greatly appreciated. Thank you for your time.
Main information
The server can `ping 8.8.8.8`, but cannot `ping google.com` (`Name or service not known`). My `/etc/resolv.conf` contains:
Code:# 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
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.
nameserver 8.8.8.8
nameserver 127.0.0.53
options edns0This is the contents when it is regenerated using `resolvconf -u`.
Previously when I had manually added `nameserver 8.8.8.8` to the top of `/etc/resolv.conf`, I was able to `ping google.com`, but other services (see long version) still seemed to be failing in some way. However, since I've attempted some other fixes, such as `sudo apt install --reinstall resolvconf network-manager libnss-resolve` and others, even the presence of `nameserver 8.8.8.8` in `/etc/resolv.conf` does not seem to allow `ping google.com` to work. I'm also now unsure of where `nameserver 8.8.8.8` is being added from during a `resolvconf -u`, as none of `/etc/systemd/resolved.conf`, `/etc/resolvconf/resolv.conf.d/head`, or `/etc/resolvconf/resolv.conf.d/base` seem to contain this entry, and `/etc/network/interfaces.d/` is empty.
My `systemd-resolve --status` appears as:
Code:Global
DNS Servers: 8.8.8.8
8.8.4.4
DNSSEC NTA: 10.in-addr.arpa
16.172.in-addr.arpa
168.192.in-addr.arpa
17.172.in-addr.arpa
18.172.in-addr.arpa
19.172.in-addr.arpa
20.172.in-addr.arpa
21.172.in-addr.arpa
22.172.in-addr.arpa
23.172.in-addr.arpa
24.172.in-addr.arpa
25.172.in-addr.arpa
26.172.in-addr.arpa
27.172.in-addr.arpa
28.172.in-addr.arpa
29.172.in-addr.arpa
30.172.in-addr.arpa
31.172.in-addr.arpa
corp
d.f.ip6.arpa
home
internal
intranet
lan
local
private
test
Link 11 (veth399f989)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 9 (vethc76fcf1)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 7 (vethbb5aff2)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 5 (br-ad7981a8fd08)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 4 (docker0)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 3 (eno2)
Current Scopes: DNS
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
DNS Servers: 134.74.128.7
134.74.192.2
DNS Domain: ~.
Link 2 (eno1)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: noAdditional information
I originally set up this server for my PhD advisor when I was student 5 or so years ago. Primarily, they use this server to host a WordPress site and a MediaWiki site that I set up at the time. This has continued to work fine for the last 5 years.
The original sign of some issue was that, recently, for both the WordPress site and the MediaWiki site, any page updates began to fail. For example, the MediaWiki pages can still be viewed, but upon attempting to submit an edit to a page, the user receives a timeout. On the server, Nginx receives the POST, PHP seems to execute the appropriate script for the post, but then the page is left un-updated. I'm not finding any errors in any of the Nginx, PHP, or database logs. Given that there are the other DNS issues made obvious from the above pinging, I suspect that the server is sending requests to itself, but due to these DNS issues, these requests are never really sent or received.
The server is behind a university controlled entry point, then a lab router. I no longer have physical access to the machine, but I can periodically have someone go in to physically access the machine when needed. As part of my attempts to fix it, at one point I had run a package update followed by a reboot. For one reason or another, the reboot did not complete, and the machine only shutdown. Someone had to be sent in physically to turn the machine back on for me. So with my other fixes, I would hope to avoid trying solutions that require reboots, though, I understand this often may be required.
I am far from an expert in either unix related topics or networking topics, so I apologize in advance for any obvious mistakes or troubleshooting that I haven't checked.
Any suggestions would be greatly appreciated. Thank you for your time.