How to Flush DNS Cache of Linux and Windows Client
Posted on In LinuxWe may need to flush DNS cache of our client when the site’s DNS has been changed.
Table of Contents
Flush DNS cache of Linux with NetworkManager/dnsmasq
You may simply restart NetworkManager by
sudo systemctl restart NetworkManagerFlush DNS Cache on (Old) Linux with nscd
1) Use su – to get root privilege or sudo with the following command:
# /etc/rc.d/init.d/nscd restart
or
# service nscd restart
Flush DNS Cache on Windows:
1) Log in as a Administrator on Windows XP and previous version.
2) “Start->run” then run “cmd.exe”.
3) At the command prompt run
ipconfig /flushdns
For Windows Vista, Windows 7 and later version:
1) “Start->All Programs->Accessories”
2) Right click on the command prompt and choose run as administrator.
3) At the command prompt run
ipconfig /flushdns
Flush DNS cache of Chrome
Open the URI:
chrome://net-internals/#dnsin Chrome’s address bar.
Then click the “Clear host cache” button in the configuration page.
The DNS may be probably also cached by your DNS provider. You can use the dig command to query the DNS info from your DNS server:
dig @dns_server_address domain_nameFor example:
[zma@localhost ~]$ dig @ns1.dreamhost.com fclose.com
; <> DiG 9.9.4-P2-RedHat-9.9.4-12.P2.fc20 <> @ns1.dreamhost.com fclose.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52886
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 2800
;; QUESTION SECTION:
;fclose.com. IN A
;; ANSWER SECTION:
fclose.com. 14400 IN A 64.90.49.224
;; Query time: 921 msec
;; SERVER: 66.33.206.206#53(66.33.206.206)
;; WHEN: Mon Apr 21 14:01:50 HKT 2014
;; MSG SIZE rcvd: 55
[zma@localhost ~]$ dig @8.8.8.8 fclose.com
; <> DiG 9.9.4-P2-RedHat-9.9.4-12.P2.fc20 <> @8.8.8.8 fclose.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15587
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;fclose.com. IN A
;; ANSWER SECTION:
fclose.com. 14399 IN A 64.90.49.224
;; Query time: 1865 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Mon Apr 21 14:01:59 HKT 2014
;; MSG SIZE rcvd: 55
You may also need to flush certain programs’ own DNS cache.
For example, for Chrome, “browse”
chrome://net-internals/#dnsAnd click on the “Clear host cache” can clear Chrome’s DNS cache.
On Fedora 22, it seems there is no dns caching in the system level with NetworkManager:
No configuration about `dns=dnsmasq` in /etc/NetworkManager/NetworkManager.conf .
About NetworkManager configuration: https://blogs.gnome.org/dcbw/2015/02/16/networkmanager-for-administrators-part-1/