Clearing the DNS cache

[ron.alan]

So I wanted to clear my DNS cache and did a search for how to do it. So I found (from here) to run either sudo /etc/init.d/networking restart or sudo service networking restart. When I ran them (I ran both) I got a message that it was deprecated. The exact message on both was:

Running /etc/init.d/networking restart is deprecated because it may not re-enable some interfaces ... (warning).
Reconfiguring network interfaces...done.

So I have two questions: 1) Did one, or both, of these commands work or not? 2) Is there a better way to clear the DNS cache?

I'm on Devuan GNU/Linux 5.

 

[Aristarchus]

I used Devuan some time ago at very early stages of Devuan development so I don't remember which DNS resolver do you have.
You need to find this out.
Anyway here are some options for flushing DNS cache:
NCSD: sudo /etc/init.d/nscd restart
Dnsmasq: sudo /etc/init.d/dnsmasq restart
or
sudo killall -USR1 dnsmasq
then check file size (should be "0" - zero):
tail -f n1000 /var/log/syslog | grep "cache size"
BIND: You may have to try multiple commands:
sudo /etc/init.d/named restart
sudo rndc restart
sudo rndc exec

Hopefully one of these will help

 

[ron.alan]

So are you saying that what I did didn't clear the DNS cache? What does the line "Reconfiguring network interfaces...done." mean?
How do I find out what resolver I have?

EDIT
So I opened synaptic and searched for "DNS" and of what came from the search, I have bind9-host installed, if this means anything.

 

[craigevil]

sudo systemctl restart bind9

If you are using systemd-resolve
sudo resolvectl flush-caches

If you are using an older version of systemd (before v239), use this command instead:
sudo systemd-resolve --flush-caches

How to flush the DNS cache in Debian?

How can I flush the DNS cache in Debian 9.1 with KDE?

unix.stackexchange.com

 

[ron.alan]

I have bind9 installed, but when I run systemctl is-active named in the terminal it says it isn't running:

$ systemctl is-active named
ERROR:systemctl:Unit named.service could not be found.
unknown

I also get a negative response for systemd-resolved (obviously), Dnsmasq, and nscd.

 

[leftyleo]

i use :

sudo /etc/init.d/nscd restart

But it is rare that i have to use it. The last time i used it was because Amazon Prime Video player was having an issue and throwing a 7031 (?) error -- the the recommended fix was to clear/restart the DNS server.
-- Though I dont know why this was an issue, it did in fact clear the trouble.

 

[CaffeineAddict]

I have bind9-host installed, if this means anything.

That's all that matters, here are steps:

https://linuxconfig.org/how-to-view-and-clear-bind-dns-server-s-cache-on-linux

 

[ron.alan]

That's all that matters, here are steps:

It's installed, but like I wrote in my last post, it's not active. Running the command in your link proves it:

$ sudo rndc flush
[sudo] password for ron:
sudo: rndc: command not found

 

[Aristarchus]

two things:
1) this is ncd not mcd (unless typo here):
sudo rndc restart
sudo rndc exec

so this is r n d c

2) if you don't have DNS running there is nothing to flush.

 

[ron.alan]

this is ncd not mcd

I didn't mistype an "m" as I did a copy and paste. You can see that in the results I posted.

if you don't have DNS running there is nothing to flush.

I'm confused. Doesn't there have to be some DNS service running? I thought that was necessary to browse the internet.

 

[f33dm3bits]

I'm confused. Doesn't there have to be some DNS service running? I thought that was necessary to browse the internet.

No, the dns servers are part of your network configuration for your system. No need to have a caching service running, dns servers however do have a cache, so that they don't need to request something again when another client requests the same as a previous client, which is where TTL comes from in dns records.

 

[f33dm3bits]

No, the dns servers are part of your network configuration for your system.

There do exist caching services which you can run on your client from what I remember from a topic but you will have to install it yourself. And if you are using systemd-resolved could be that it has some caching thing integrated into it but from what I remember you are running a distribution that doesn't use systemd. For example.

dnsconfd : Local DNS cache configuration daemon

 

[GatorsFan]

Since you are using Devuan you do not need to flush the DNS Cache it does not cache DNS lookups - depending if you installed it with SysVInit or RunIt - since there is no systemd any systemd commands will not work such as systemctl
You router may cache them but all non-systemd Linux OSes do not DNS cache as far as I know

 

[leftyleo]

Since you are using Devuan you do not need to flush the DNS Cache it does not cache DNS lookups - depending if you installed it with SysVInit or RunIt - since there is no systemd any systemd commands will not work such as systemctl
You router may cache them but all non-systemd Linux OSes do not DNS cache as far as I know

Does this mean that you should also clear the DNS in the router?

 

[ron.alan]

Does this mean that you should also clear the DNS in the router?

I did see something about that. It said to simply unplug the router and then plug back it.

 

[GatorsFan]

Does this mean that you should also clear the DNS in the router?

To clear your router you only have to reboot it or as @ron.alan has stated

 

[leftyleo]

Thank you -- i didint think a simple reboot was all you have to do