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Author Topic: Flushing DNS cache  (Read 1535 times)

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Offline stefanreich

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Flushing DNS cache
« on: April 29, 2017, 01:14:19 pm »
Hi,

I think my local cache resists flushing:

Code: [Select]
stefan@stefan-quadcore ~ $ nslookup ai1.lol
Server: 127.0.1.1
Address: 127.0.1.1#53

Non-authoritative answer:
Name: ai1.lol
Address: 217.70.184.38

(WRONG! This is a DNS entry I had temporarily whilst moving to CloudFlare and then back.)

However:

Code: [Select]
stefan@stefan-quadcore ~ $ nslookup ai1.lol 8.8.8.8
Server: 8.8.8.8
Address: 8.8.8.8#53

Non-authoritative answer:
Name: ai1.lol
Address: 69.10.46.185

(RIGHT.)

Even rebooting didn't clear the entry. This is Peppermint 7.

How to flush?  8)
« Last Edit: April 29, 2017, 01:18:21 pm by stefanreich »

Online VinDSL

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Re: Flushing DNS cache
« Reply #1 on: April 29, 2017, 03:15:58 pm »
If I'm reading the situation correctly ...

You're trying to clear the cache on the Google public DNS server.

If that's what you're trying to do, it's impossible.

Why are you trying to do this ... trying to propagate changes for this website   :-\
« Last Edit: April 29, 2017, 03:19:12 pm by VinDSL, Reason: Addendum »

Online VinDSL

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Re: Flushing DNS cache
« Reply #2 on: April 29, 2017, 03:27:59 pm »
That's an interesting site !   8)


Offline stefanreich

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Re: Flushing DNS cache
« Reply #3 on: April 29, 2017, 06:24:43 pm »
lol uh... thanks? :-) We're remaking AI  :D

That's an interesting site !   8)

Offline stefanreich

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Re: Flushing DNS cache
« Reply #4 on: April 29, 2017, 06:26:15 pm »
If I'm reading the situation correctly ...

You're trying to clear the cache on the Google public DNS server.

If that's what you're trying to do, it's impossible.

Nooo... I am trying to clear my local machine's DNS cache which got filled with a wrong address during some DNS changes I made. Google's server has the right address.

By now my machine has refreshed the DNS entry by itself, so... all fine anyway. Still I would like to know how to flush Peppermint's DNS cache. Peppermint runs dnsmasq for DNS caching, no?

Cheers  :)
Stefan

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Re: Flushing DNS cache
« Reply #5 on: April 29, 2017, 07:24:26 pm »
Is it not still
Code: [Select]
sudo /etc/init.d/dns-clean
?

I've never had to flush the DNS cache in Linux.
« Last Edit: April 29, 2017, 07:26:51 pm by PCNetSpec »
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Online VinDSL

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Re: Flushing DNS cache
« Reply #6 on: April 29, 2017, 07:32:46 pm »
Or, this ...   8)

Code: [Select]
sudo /etc/init.d/networking force-reload

Online VinDSL

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Re: Flushing DNS cache
« Reply #7 on: April 29, 2017, 07:44:14 pm »
I've never had to flush the DNS cache in Linux.

Dittos ...

I was under the impression that Ubu desktops don't have local DNS caches, for security reasons.  I know they do on servers, cloud images, etcetera, but that's a different discussion.

I *think* the locally launched 'dnsmasq-base' is configured effectively as a local DNS server, but all it does is forward requests to 'real' DNS servers.

Interesting ! 

Online VinDSL

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Re: Flushing DNS cache
« Reply #8 on: April 29, 2017, 09:32:17 pm »
Aha !  Do we believe Stack Overflow ?!?!?   ;D

SOURCE:  DNS cache on Ubuntu 

Quote
Is it true that Ubuntu doesn't have DNS cache by default?

Quote
Ubuntu Desktop have dnsmasq-base package built-in in NetworkManager, but with the dns cache function disabled.


If we do believe them, then it just amounts to slow propagation (on 'real' DNS servers].

I always factor in a 24 hour wait, for DNS changes to take effect worldwide.
« Last Edit: April 29, 2017, 10:06:42 pm by VinDSL, Reason: Addendum »

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Re: Flushing DNS cache
« Reply #9 on: April 29, 2017, 09:45:24 pm »
And, then there's the Reddit crowd ...  ::)

SOURCE:  What happened to the talk about implementing per-user dns cache?

Quote
I was tinkering with Gevent the other day and kept wondering why the multi-threading performance was crapping out so badly. Did some digging and found out that Ubuntu always sending new DNS query on each job spawned when it should normally cache the DNS reply. Turned out that local DNS caching has been turned off by default in Network Manager's dnsmasq since 11.x release over concern with DNS cache poisoning according to this talk.



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Re: Flushing DNS cache
« Reply #10 on: April 29, 2017, 10:25:15 pm »
In case one feels compelled to enable local DNS caching, in the name of speed, caveat emptor ...



Offline stefanreich

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Re: Flushing DNS cache
« Reply #11 on: January 15, 2019, 04:29:28 pm »
I've seen something similar today... Peppermint insisting it doesn't know a certain host. Even after reboot. Had to add the host to /etc/hosts...