Comments on: Howto clear/Flush DNS Cache in Ubuntu

By: Juegos

Juegos — Mon, 19 Sep 2011 01:45:31 +0000

Great thank you as I can see, for me runs /etc/init.d/dns-clean
I have not installed too the nscd by default. i’ll install it roght now, and test.

Greetens and thanks!

By: Arash pazandi

Arash pazandi — Mon, 12 Sep 2011 12:17:23 +0000

hi guys
you must be type first
sudo apt-get install nscd
and after install successfully nscd Service .
for restart type it :
sudo /etc/init.d/nscd restart

just do it !

By: Billy LaRocque

Billy LaRocque — Fri, 02 Sep 2011 21:59:09 +0000

Dudes, I have been using *NIX systems since ’79 and there is no DNS cache in UNIX or LINUX (think someone mentioned it above). The only cache is in your browser, usually closing all your browser windows will reset it. Should there be an issue still, go into Preferences (on firefox) and clear the cache manually, close and then re-open firefox.
Good Luck for those of you still struggling with installing something you don’t need on *NIX.
Cheers,
Billy

By: tcpdump

tcpdump — Wed, 10 Aug 2011 15:35:40 +0000

Hi,

full ACK to Dan.

/etc/init.d/dns-clean start will do the trick for you. if you look into the script, it calls /etc/ppp/ip-down.d/0dns-down and the last line in that script is:

[ -x /etc/init.d/nscd ] &, which means if nscd installed it will be restarted too.

regards tcpdump

By: Dan

Dan — Thu, 16 Jun 2011 23:36:42 +0000

Why would you want to install something extra when Ubuntu already comes with it’s own DNS caching service (dns-clean)?

The dns-clean service runs at every boot, so a simple reboot of Ubuntu cleans out your DNS anyway.

If you don’t feel like rebooting:

sudo /etc/init.d/dns-clean start

By: kim

kim — Fri, 03 Jun 2011 12:30:59 +0000

i don’t need to install nscd. thanks

By: Systems

Systems — Fri, 10 Dec 2010 14:01:03 +0000

Is Wrong In ubuntu Is this command sudo apt-get install nscd and After sudo /etc/init.d/nscd restart

ubuntu10@ubuntu10-virtual-machine:/etc/init.d$ sudo apt-get install nscd
Reading package lists… Done
Building dependency tree
Reading state information… Done
The following NEW packages will be installed:
nscd
0 upgraded, 1 newly installed, 0 to remove and 188 not upgraded.
Need to get 207kB of archives.
After this operation, 381kB of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu/ maverick-updates/universe nscd i386 2.12.1-0ubuntu9 [207kB]
Fetched 207kB in 0s (400kB/s)
Selecting previously deselected package nscd.
(Reading database … 120088 files and directories currently installed.)
Unpacking nscd (from …/nscd_2.12.1-0ubuntu9_i386.deb) …
Processing triggers for man-db …
Processing triggers for ureadahead …
Setting up nscd (2.12.1-0ubuntu9) …
* Starting Name Service Cache Daemon nscd [ OK ]
ubuntu10@ubuntu10-virtual-machine:/etc/init.d$ sudo /etc/init.d/nscd restart
* Restarting Name Service Cache Daemon nscd [ OK ]
ubuntu10@ubuntu10-virtual-machine:/etc/init.d$

By: Delrey

Delrey — Sat, 23 Oct 2010 14:06:30 +0000

Since I am no expert (by far). I’m having similar issue I’m hoping someone can shed light to. I have Ubuntu 10.04 64bit installed on a Lenovo Z61T. Docked most of the time I have NO issues with networking or resolving DNS. I also have another Lenovo X200 dual boot with Windows 7 and Ubuntu 10.04LTS 64bit. My problem is with either laptop and only using Ubuntu DNS seems to fail resolving after a short of use. I can still ping thru and whe compared to Windows (unfortunately) I have no problems. Reading some other posts seems to indicate and issue with IP6. I was tempted to totally remove by following some hacks but I’m not yet convinced its a bug probably something I have overlooked or just naive to as a newbe. my instincts say try a tcp dump but thought I would post here to save more aggravation

By: cebu travel guide

cebu travel guide — Sun, 29 Aug 2010 08:49:43 +0000

finally did it.
i thought i don’t need to install nscd. thanks

ubuntu should have it by default

By: srweb

srweb — Tue, 24 Aug 2010 17:30:28 +0000

I’m having the same problem!!! TOO

By: takizo

takizo — Mon, 26 Jul 2010 14:21:54 +0000

@Brian, it has nothing to do with DNS when you do IP ping. It’s more like your host is having problem to reach.

By: Ryan

Ryan — Thu, 18 Feb 2010 17:59:46 +0000

@Brian: No, it doesn’t. It’s because ping uses C library functions like gethostbyname, and so follows the order directive (/etc/nsswitch.conf, /etc/hosts, locally running bind daemons, etc.). On the other hand, utilities like dig and nslookup were meant to query nameservers only and could care less about that crap, because they were meant to query nameservers only without taking any of the local superseding entries in to account. So, it is not surprising that you’re seeing different responses. To the trained eye, this is a benefit, not a hindrance, because it points out where the problem is, which in this case is your Ubuntu machine’s configuration. Installing nscd is pointless and irrelevant in this situation, and will only complicate your problems. There are more files that just resolv.conf that control the behavior you’re seeing from utilities like ping - resolv.conf, nsswitch.conf, /etc/hosts, /etc/hostname, so on and so forth. Google or read the manpages, or keep chasing ghosts. It’s up to you.

By: Brian

Brian — Tue, 01 Dec 2009 16:56:30 +0000

Sorry, that ping response should have read:
From 192.168.0.67 icmp_seq=1 Destination Host Unreachable

(While changing the addresses and names to protect the innocent, I missed a line).

By: Brian

Brian — Tue, 01 Dec 2009 16:53:48 +0000

I’ve got a similar problem…

The program ‘nscd’ is currently not installed.

“typho” is a computer on my network. “nslookup typho” returns:

Name: typho.example.com
Address: 192.168.0.64

This is correct (verified by walking over to typho and typing “ipconfig”). Yes, it is a WinXP machine.

However, “ping typho” returns with:
PING 192.168.0.65 (192.168.0.65) 56(84) bytes of data.
From 192.168.139.67 icmp_seq=1 Destination Host Unreachable

My IP address is 67, but typho is 64, *not* 65. A few *weeks* ago it *was* 65, but I changed it on my DNS server.

In fact, every application I’ve tried (except nslookup) is resolving typho to 65, including Nautilus (smb://typho/share), ftp, and others.

“ping 192.168.0.64″ looks good, so there is a connection:

PING 192.168.0.64 (192.168.0.64) 56(84) bytes of data.
64 bytes from 192.168.0.64: icmp_seq=1 ttl=128 time=0.976 ms

Rebooting does not solve this. There is clearly a dns cache somewhere, and it is not being updated with the correct information. Other Ubuntu machines on my network can “ping typho” correctly (they automatically resolve the correct address).

My /etc/resolv.conf is simply:
# Generated by NetworkManager
domain example.com
search example.com
nameserver 192.168.0.40

That is correct. My nameserver is located at 40.

Other Ubuntu machines on my network have the same resolv.conf.

What’s going on here? Where is the cache, and how do I flush it?

Thanks,

By: alex dekker

alex dekker — Wed, 25 Nov 2009 21:16:51 +0000

thomas, if the command isn’t found, that’s because NSCD isn’t installed. If NSCD isn’t installed, then there’s no cache to flush!

By: Jan

Jan — Tue, 03 Nov 2009 16:42:37 +0000

I just had a similar problem… dns updated, but nslookup or ping gave the old address.
Turns out that it was my own DNS server that was lacking updates! I switched my /etc/resolv.conf to use opendns.org’s servers and the updates came through immediately!
nothing to flush on a ubuntu or other linux system unless you specifically install software to cache dns queries, like nscd.
If you are brave enough to “restart” your network on a live server, good luck to you! “/etc/init.d/networking restart” will stop all networking for a split second on all connected network cards. If you’re running services that other people depend on, not such a good idea.

By: Flush DNS

Flush DNS — Fri, 18 Sep 2009 23:35:24 +0000

For those not as technical a good old fashioned reboot seems to work just fine for me too.

By: tehhi5

tehhi5 — Wed, 01 Jul 2009 18:32:34 +0000

How to flush the DNS Resolver Cache if temporary problems are preventing accessing a

particular website. Windows XP caches DNS entries (these change human-readable names such

as malektips.com and google.com into IP addresses that allow communication over the

Internet). This way instead of having to access a remote DNS server every time you

re-access the same web address, Windows can use the cached entry to speed communication.

By: thomas

thomas — Thu, 07 May 2009 23:14:12 +0000

For people companing about command not found problem, try “sudo bash /etc/…” (bash after sudo)

By: Gerry

Gerry — Fri, 16 Jan 2009 15:15:12 +0000

Totally agree with Hackel. Also “sudo aptitude install nscd” requires your DNS to be working, which is pointless if you’re needing to flush the cache because you’ve just switched over to a working dns. You have to have a working dns before you can flush the dns that isn’t working… hmmm that’s logical.

Under Ubuntu I was able to get the new dns entry working by reselecting my network connection.