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How can I check which DNS server am I using (in Linux)? I am using network manager and a wired connection to my university's LAN. (I am trying to find out why my domain doesn't get resolved)

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    The Linux kernel itself is not aware about DNS services. To answer it's better to know your userland. What distribution are you using? Ubuntu? Debian GNU/Linux? Centos? Commented May 18, 2021 at 7:49

15 Answers 15

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You should be able to get some reasonable information in:

$ cat /etc/resolv.conf
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    However, please be aware that (on modern Linuxen) the contents of /etc/nsswitch.conf dictate what name services are used (DNS, LDAP, etc) and in what order. Say fgrep hosts: /etc/nsswitch.conf. If it only references DNS, /etc/resolv.conf is the right place to look for your nameservers. But chances are you're also using mDNS (aka ZeroConf, aka Avahi, aka Bonjour, etc), etc. In that case, things depend on what you're using. Commented Jan 12, 2012 at 13:35
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    This file typically points at 127.0.1.1 on Ubuntu - it's the local DNS cache server, not the actual upstream. Commented Mar 8, 2016 at 10:24
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    And if you have several upstream server configured ? How to know which one is currently used ? Commented Nov 24, 2016 at 23:31
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    See the answers by @G32RW or @Lonniebiz for a more robust approach under various circumstances, e.g. when you get an answer like 127.0.0.53 Commented Nov 11, 2018 at 22:13
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    This solution is no more up to date. I find the systemd-resolve --status suggested by @G32RW most up-to-date solution for this problem. Commented Mar 27, 2019 at 15:59
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Here's how I do it:

( nmcli dev list || nmcli dev show ) 2>/dev/null | grep DNS

This worked previous to the way above:

nm-tool | grep DNS

On Debian, you need to have the network-manager package installed.

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    This one is usefull if you are using VPN and NetworkManager. Your /etc/resolv.conf will point to your machine, with dnsmasq resolving names as configured by NetworkManager. Commented May 30, 2013 at 11:32
  • nm-tool | grep DNS No command 'nm-tool' found, did you mean: Command 'dm-tool' from package 'lightdm' (main) nm-tool: command not found Commented Aug 31, 2016 at 7:22
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    This did not work for me on an Ubuntu VM. nmcli dev show did not have the DNS info. However, systemd-resolve --status did have the real DNS server. unix.stackexchange.com/a/434756 Commented Nov 14, 2018 at 2:22
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    To add, you can also supply an interface name, e.g., nmcli dev show eth1 to show information about a specific adapter. Useful if you're troubleshooting a specific adapter that's connected differently than others. Commented Jun 30, 2019 at 23:52
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    The question specifically indicates the use of Network Manager. If you're not using network manager, see other answers. Commented Nov 18, 2021 at 13:46
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On systems running systemd use:

systemd-resolve --status

Or:

resolvectl
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    systemd-resolve: unrecognized option '--status' Commented Apr 1, 2018 at 18:03
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    Says Failed to get global data: Unit dbus-org.freedesktop.resolve1.service not found. Commented Apr 12, 2018 at 11:19
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    This is the new default way to do it in Ubuntu 18.04 Bionic Beaver - get used to it, everybody! Commented Apr 24, 2018 at 20:32
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    What am I reading? I only see DNSSEC records. Commented May 2, 2020 at 16:22
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    resolvctl worked for me in Ubuntu 22.04 . nmcli and systemd-resolve solutions did not work. Commented Nov 25, 2022 at 17:28
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I think you can also query DNS and it will show you what server returned the result. Try this:

dig yourserver.somedomain.xyz

And the response should tell you what server(s) returned the result. The output you're interested in will look something like this:

;; Query time: 91 msec ;; SERVER: 172.xxx.xxx.xxx#53(172.xxx.xxx.xxx) ;; WHEN: Tue Apr 02 09:03:41 EDT 2019 ;; MSG SIZE rcvd: 207

You can also tell dig to query a specific DNS server by using dig @server_ip

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    On Debian this requires the dnsutils package. Commented Jan 14, 2012 at 20:54
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    If you use any DNS masking/caching service that is run on your local machine, it will hide the real DNS servers. Commented Sep 7, 2015 at 9:12
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    Ubuntu 18.04 just shows the local dns cache: SERVER: 127.0.0.53#53(127.0.0.53) Commented Nov 14, 2018 at 2:16
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    This only tells you which server was used for that query. It doesn't tell you all the DNS servers that your host might use. Commented Nov 28, 2021 at 1:14
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    Beware that this obviously fails if the DNS server is not available. That's not a common thing, but I've managed to get a bad result or timeout when looking for a DNS server running on IPv6 (using dig -6). Commented Oct 27, 2022 at 13:03
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Just do an, nslookup. Part of its results include the server that it's using.

In the example below, it shows that the DNS server used is at 8.8.8.8. 

$ nslookup google.com Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: Name: google.com Address: 172.217.22.174
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    On Debian this requires the dnsutils package. Commented Aug 13, 2017 at 7:00
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    On a recent Ubuntu, this again points to the local cache server 127.0.0.1 as already hinted at in this comment Commented Dec 1, 2017 at 1:50
  • In CentOS 7 it quits with error, but it is a vm so I did nslookup google.com in the Windows host and I found the nameserver. Add it in /etc/resolv.conf like: nameserver xx.xx.xx.xx and restart service network, and all is fine. Praise you. Commented May 3, 2018 at 15:22
  • Note that Nslookup is deprecated Commented Mar 13, 2020 at 1:22
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    Didn't work: Server: 127.0.0.53, Address: 127.0.0.53#53 Commented May 26, 2021 at 19:38
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With the new network-manager command nmcli, do this:

nmcli --fields ipv4.dns,ipv6.dns con show [connection_name]

On newer versions of network-manager (such as in Ubuntu 16.04), the field names are slightly different:

nmcli --fields ip4.dns,ip6.dns con show [connection_name]

If you don't know the connection name, use:

nmcli -t --fields NAME con show --active

For example, on old versions of nmcli :

$ nmcli --fields ip4.dns,ip6.dns con show 'Wired connection 1' IP4.DNS[1]: 172.21.0.13 IP4.DNS[2]: 172.21.0.4
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  • My results: order «con» «show» is not valid. Commented Jan 30, 2016 at 22:03
  • It works fine for me with network-manager 1.0.4 on Ubuntu 15.10. Maybe you have an older version? Commented Mar 17, 2016 at 5:40
  • The tabular format is pretty bad. I hope to get a column like format similar to Powershell. Commented Mar 14, 2017 at 6:42
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    Returns Error: invalid field 'ip4.dns'; allowed fields: NAME,UUID,TYPE,TIMESTAMP,TIMESTAMP-REAL,AUTOCONNECT,AUTOCONNECT-PRIORITY,READONLY,DBUS-PATH,ACTIVE,DEVICE,STATE,ACTIVE-PATH. Commented Dec 1, 2017 at 1:53
  • Ugh, as long as nmcli doesn't keep backwards compatibility with specific parameters and output format, I guess this is not a good way of testing for anything. Commented Oct 27, 2022 at 13:06
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Using resolvectl

$ resolvectl status | grep -1 'DNS Server' DNSSEC supported: no Current DNS Server: 1.1.1.1 DNS Servers: 1.1.1.1 1.0.0.1

grep option: -C NUM, -NUM, --context=NUM Print NUM lines of output context.

For compatibility, systemd-resolve is a symbolic link to resolvectl on many distros as for Ubuntu 18.10:

$ type -a systemd-resolve systemd-resolve is /usr/bin/systemd-resolve $ ll /usr/bin/systemd-resolve lrwxrwxrwx 1 root root 10 nov. 15 21:42 /usr/bin/systemd-resolve -> resolvectl $ type -a resolvectl resolvectl is /usr/bin/resolvectl $ file /usr/bin/resolvectl /usr/bin/resolvectl: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=09e488e849e3b988dd2ac93b024bbba18bb71814, stripped
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    works perfect on Ubuntu 18.10. Commented Mar 27, 2019 at 16:02
  • see also askubuntu.com/q/1149364/157358 about the name of the program Commented Jun 12, 2021 at 11:38
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    As with other answers, thiis will simply return the caching service on your local host. Commented Oct 27, 2022 at 13:09
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to get the first DNS SERVER (IP only) :

cat /etc/resolv.conf|grep -im 1 '^nameserver' |cut -d ' ' -f2
  • cat will output DNS config
  • grep filters only nameserver
  • -i grep ignore case
  • -m 1 grep stop after first match
  • cut take the ip part of the row (second column with ' ' as separator)

If you prefer sed:

 cat /etc/resolv.conf | sed -rn "s/^nameserver ([.0-9]*).*$/\1/p"
  • Sed command: after nameserver return everything what is a number or a dot.

To put DNS ip in an environment variable, you could use as follow:

export THEDNSSERVER=$(cat /etc/resolv.conf|grep -im 1 '^nameserver' |cut -d ' ' -f2)
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    To lighten the pipeline even more, capture groups with Perl regexp is very neat, and grep takes a file argument: grep -Pom 1 '^nameserver \K\S+' /etc/resolv.conf. Just wrote up Capture groups with grep perl regular expression Commented Jul 28, 2017 at 9:04
  • There's both IPv4 and IPv6 DNS servers. Also, secondary servers exist for a reason. Which one this command returns? Is it advised to take the first one, and just ignore the others? Commented Jan 16, 2020 at 2:53
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If you are using network manager probably you get all network parameters from your dhcp server at your university.

If you don't want use your shell to check your dns settings (as described by hesse and Alexios), you can see them from the panel "Network information".

You can reach this panel by pressing right mouse button on network manager icon and selecting "Connection Information" from the menu.

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I have Fedora 25 and also had similar slow response on command line to sudo commands.

nmcli dev show | grep DNS

showed that only one of my 3 adapters (two active) had DNS entries. By adding DNS entries to the one active card that didn't have an entry - presto! All is good and response time is immediate.

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  • perhaps alternatively Commented Jun 12, 2019 at 17:44
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In Ubuntu >= 15

nmcli device show <interfacename> | grep IP4.DNS

Replace <interfacename> with yours.

In Ubuntu <= 14

The command

 nmcli dev list iface <interfacename> | grep IP4

Replace <interfacename> with yours.

Examples

 nmcli device show eth0 | grep IP4.DNS

Or

 nmcli dev list iface eth0 | grep IP4

This will list all DNS servers(If you use more than one).

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On a recent Fedora 33, you can just use

# resolvectl dns Global: Link 2 (enp0s31f6): Link 3 (wlp4s0): 1.1.1.1 8.8.8.8 Link 4 (virbr0): Link 5 (virbr0-nic):

To check if systemd-resolved is active, do cat /etc/resolv.conf It will tell you who is controlling the file.

If you want more details, you can use resolvectl status resolvectl statistics, you can also flush caches ...

To troubleshoot, you can use journalctl -u systemd-resolved -f -o cat | grep Looking after setting the level to DEBUG: sudo resolvectl log-level debug

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  • Only returns local caching DNS, i.e. localhost. Commented Oct 27, 2022 at 13:11
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On systems where systemd-resolved is NOT installed :

$ host -v something.unknown | awk -F "[ #]" '/Received /{print$5}' | uniq 192.168.1.1

On systems where NetworkManager is running :

$ ( nmcli -f IP4.DNS,IP6.DNS dev list || nmcli -f IP4.DNS,IP6.DNS dev show ) 2>/dev/null | awk '/DNS/{print$NF}' 192.168.1.1
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Some dudes use tcpdump and are happy with the result:

tcpdump -i any port 53
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    You may want to add some explanation on how to interpret the result, which is not completely trivial. Also, you should probably mention that this requires triggering the corresponding traffic in the first place. In addition, using that tool usually requires root privileges. Commented Oct 18, 2024 at 12:56
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In CentOS, you can use: 

/usr/sbin/named -v
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