Linux mint flush dns cache

Как очистить / сбросить кеш DNS в Linux

В некоторых случаях вам трудно добраться до некоторых сайтов из-за проблемы с DNS, возможно, ваш локальный DNS-кеш поврежден.

Для такой ситуации вам необходимо перезапустить службу кэширования DNS операционной системы.

Кэш-память DNS для системы доменных имен – это временная база данных, которая поддерживается операционной системой компьютера, которая содержит IP-адрес сайтов, которые вы недавно просматривали.

См. Ниже список основных серверов кэширования DNS, используемых в дистрибутиве Linux.

• nscd DNS cache
• dnsmasq dns cache
• BIND server dns cache

nscd DNS Cache: nscd – демон кэша службы имен, Nscd – это демон, который обеспечивает кэш для наиболее распространенных запросов службы имен.

Файл конфигурации по умолчанию, /etc/nscd.conf

dnsmasq DNS Cache: Dnsmasq – легкий, небольшой в размере, простой в настройке, DNS-сервер и DHCP-сервер.

Он предназначен для предоставления DNS и опционально DHCP для небольшой сети и подходит для маршрутизаторов с ограниченным доступом и брандмауэров.

Он может обслуживать имена локальных машин, которые не входят в глобальный DNS.

Он предназначен для использования в персональных компьютерах и небольших сетях, а не для больших сетей.

BIND Server DNS Cache: BIND означает «Berkeley Internet Name Domain».

Наиболее широко используемое программное обеспечение сервера имен, BIND – это программное обеспечение с открытым исходным кодом, которое реализует протоколы доменных имен (DNS) для Интернета.

BIND на сегодняшний день является наиболее широко используемым программным обеспечением DNS в Интернете, обеспечивая надежную и стабильную платформу.

1) Очистить кеш DNS на Ubuntu / Debian / LinuxMint

Используйте приведенную ниже команду для очистки кеша DNS в системах Ubuntu / Debian / Mint.

2) Сброс кеша dns сервера BIND

Используйте приведенную ниже команду для сброса кеша BIND сервера dns

3) Очистить кэш nscd DNS

Используйте команду ниже:

4) Очистить dnsmasq dns кэш

Используйте приведенную ниже команду для стирания кеша dnsmasq server dns

5) Очистка кеша dns в Windows

Используйте приведенную ниже команду для очистки кеша dns в Windows:

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How to Clear/Flush the DNS Cache on Linux

You may need to flush or clear the local DNS cache on your Linux system for various reasons.

This could be one of the below reasons.

• Sometimes you may have difficulty reaching certain websites.
• When troubleshooting network related issues.
• After DNS resolvers change.

When you run flush DNS cache, this will destroy the DNS entries in the cache and perform a subsequent query to resolve the domain based on the newly configured DNS settings.

What is DNS cache and what it Does?

The DNS cache is a temporary database maintained by the computer’s operating system.

It stores information about previous DNS lookups (like information on recently visited websites and other web domains).

This will quickly resolve DNS queries when you visit the cached website by getting details from the local DNS database instead of the actual DNS server.

If you want to know DNS information about a website, use one of the commands below.

What is nscd DNS Cache

nscd stands for name service cache daemon, nscd is a daemon that provides a cache for the most common name service requests. The default configuration file located at /etc/nscd.conf .

What is dnsmasq DNS Cache

Dnsmasq is a lightweight, small footprint, easy to configure, DNS forwarder and DHCP server. It is designed to provide DNS and optionally, DHCP, to a small network & suitable for resource constrained routers and firewalls. It can serve the names of local machines which are not in the global DNS. It is designed for personal computer use and small size networks, not for big networks.

What is BIND Server DNS Cache

BIND stands for “Berkeley Internet Name Domain”. The most widely used Name Server Software, BIND is open source software that implements the Domain Name System (DNS) protocols for the Internet. BIND is by far the most widely used DNS software on the Internet, providing a robust and stable platform.

How to Clear/Flush the DNS Cache on Linux

By default, DNS caching is not installed or enabled at the OS level, but if you have installed any of the caching services listed below, use the appropriate commands to flush them.

Below is a list of the major DNS cache services used in the Linux operating system.

• systemd Resolved Service
• nscd DNS Cache
• dnsmasq DNS Cache
• BIND server DNS Cache

1) How to Flush DNS Cache on Linux Using the systemd Resolve Service

Most modern Linux operating systems use systemd, so use the command below to flush the DNS cache.

Run the below command to check if the DNS cache service is active on your system.

You can check the DNS statistics using the below command.

If it’s active and the service is running, use the below command to flush it.

2) How to Clear BIND Server DNS Cache on Linux

The BIND DNS server is used on most servers where the Web Hosting Control Panel is installed. We have seen this on servers where cPanel and CentOS Web Panel are installed.

Run the below command to flush the BIND server DNS cache on Systemd-based Linux systems.

Run the following command to clear the BIND server DNS cache on SysVinit-based Linux systems.

Also, you can use the following commands for the BIND service.

To clear the BIND DNS cache, use the below command.

To clear DNS cache for a particular domain, use the below command.

To clear DNS cache for LAN, use the below command.

To clear DNS cache for WAN, use the below command.

3) How to Flush nscd server DNS Cache on Linux

Some Linux distributions use the nscd DNS server. If so, flush it using the below commands.

Run the below command to flush the nscd server DNS cache on Systemd-based Linux systems.

Run the following command to clear the nscd server DNS cache on SysVinit-based Linux systems.

4) How to Clear the dnsmasq Server DNS Cache on Linux

Some distribution may use the dnsmasq DNS server. If so, use the below commands to flush it.

Run the below command to flush the dnsmasq server DNS cache on Systemd-based Linux systems.

Run the following command to clear the dnsmasq server DNS cache on SysVinit-based Linux systems.

5) How to Clear the DNS Cache on Windows

Use the below command to Flush the dns cache on windows systems.

Conclusion

You have learned how to clear or flush DNS cache on Windows and Linux operating systems.

Источник

Linux Mint Forums

Welcome to the Linux Mint forums!

How do I flush the DNS cache?

How do I flush the DNS cache?

Post by markfilipak » Fri Jul 24, 2015 9:15 pm

How do I flush the DNS cache? I’m running Mint 17.1 + Xfce.

Re: How do I flush the DNS cache?

Post by karlchen » Sat Jul 25, 2015 10:17 am

Although you have rejected an answer to the same effect as not good enough before, the rejected answer seems to be correct.

The terminal command

the differences in the dnsmasq statistics might give a hint as to whether flushing the DNS cache has had any effect.

Re: How do I flush the DNS cache?

Post by xenopeek » Sat Jul 25, 2015 11:54 am

There is no DNS cache in dnsmasq on Linux Mint so the above isn’t really pertinent to the question. dnsmasq is running in non-caching mode so as to avoid cache poisoning attacks.

Command «ps -ef | grep dnsmasq» (to view running processes called dnsmasq) would return something like:

The option marked in red disables caching (see the manpage).

If you meant something else, kindly detail a bit more what you want to do (and perhaps why) or what problem you have that you are trying to solve. Likely your web browser keeps a DNS cache (for Firefox you can find plugins to clear that).

Re: How do I flush the DNS cache?

Post by markfilipak » Sat Jul 25, 2015 3:09 pm

I couldn’t be sure that person’s «answer» was correct. That person had made 10 posts and said he/she hadn’t flushed a DNS cache and had no experience. I had zero confidence.

I had performed a search before I posted and found many differring DNS caches and many seemingly conflicting ways to flush them. To a novice, too much advice is as bad (or worse) than too little advice. I just have to follow my nose because the last time I followed advice in which I had no confidence, I damaged my system (I think).

Re: How do I flush the DNS cache?

Post by karlchen » Sat Jul 25, 2015 4:37 pm

Turns out there is no way of clearing a cache which is on size 0.
I assume you have read xenopeek’s post above.
Might have noticed as well if I had checked the complete commandline here:

The crucial detail is the option » —cache-size=0«.

So the terminal commands that I gave you are irrelevant. Without any DNS cache there is no way of clearing it, and no need to do so, either.
Reading a bit more of the dnsmasq manpages would have told me that dnsmasq is run without caching.

Re: How do I flush the DNS cache?

Post by markfilipak » Sat Jul 25, 2015 6:39 pm

karlchen wrote: Hello, MarkFilipak.

Turns out there is no way of clearing a cache which is on size 0.
I assume you have read xenopeek’s post above.
Might have noticed as well if I had checked the complete commandline here:

The crucial detail is the option » —cache-size=0«.

So the terminal commands that I gave you are irrelevant. Without any DNS cache there is no way of clearing it, and no need to do so, either.
Reading a bit more of the dnsmasq manpages would have told me that dnsmasq is run without caching.

First things, first: I don’t know what «ps -ef» does. I do know that «|» is a pipe that «pipes» standard output back to standard input. I do know what «grep» is. I write lots of regexps for javascript processes. I don’t know what «dnsmasq» is.

Going to the output: I don’t know who «nobody» is. I don’t know what «1370» means. I don’t know what «826» means. I don’t know what «0» means. I don’t know what «11:29» means. I think I know what «?» means but I’m probably wrong. I don’t know what «00:00:00» means. I do know that in the «/usr/sbin/» directory there’s a program named «dnsmasq», and I know that grep is looking for the text string «dnsmasq» in standard input, but I don’t know why.

The rest of the line (beginning «—no-resolv») look like command-line switches, but I’m totally mystified by how they got into this output line and what they mean.

Re: How do I flush the DNS cache?

Post by karlchen » Sun Jul 26, 2015 4:30 am

The «ps» command — read «process list» — lists all processes which your system is currently executing. Depending on the commandline arguments which you pass to «ps» it will present the list in a different format. At the top of its list «ps» will write the column names of all thoses columns which it displays.
Knowing the column names will make the «ps» list appear much less mysterious than it looks to you without the column headers.

Yet in the given commandlines «ps axu | grep dnsmasq» and «ps -ef | grep dnsmasq» you will never see the column names.
Reason:
You send the screen output through a pipe ( |). At the other side of the pipe the command «grep» filters the output for lines holding the term «dnsmasq». I.e. «grep» will only display those lines which hold the search string «dnsmasq».
Result:
We get what we want: the complete commandline of the background process dsnmasq including all commandline arguments.

The terminal commands

which will display the help pages of the commands ps and grep and help understand what the commands do. It is all no mystery and no black magic.

Note:
It would have been possible to use a graphical programme, e.g. gnome-system-monitor, in order to extract the same piece of information, the complete dnsmasq commandline.

(Click screenshot to enlarge. Press to return here)

The popup in gnome-system-monitor actually displays the same commandline which can be found using the terminal command

Now for a few details:
«nobody» is the account under which Mint runs dnsmasq. nobody is a user with little privileges.
«1895» is the process number of dnsmasq.
«09:30» is the time dnsmasq was started up.
As said before «man ps» will help find out what ps does and what it displays.

Most important point about the dnsmasq commandline in the context of this thread:
It only served to prove that on Mint dnsmasq does not use any caching. As it does not use any caching, there is no way of emptying the cache. As simple as that.

Источник

Linux Mint Forums

Welcome to the Linux Mint forums!

Flush DNS

Flush DNS

Post by chazb » Fri Jun 30, 2017 2:58 am

Re: Flush DNS

Post by Hoser Rob » Fri Jun 30, 2017 2:07 pm

I did a quick search of «ubuntu flush dns» . I always prefix my mint searches of this sort with ‘linux’ or ‘ubuntu’ . and this is worth reading .

. and if you need to do it the command is in that thread somewhere.

Re: Flush DNS

Post by chazb » Fri Jun 30, 2017 3:26 pm

Re: Flush DNS

Post by Petermint » Tue Apr 03, 2018 9:17 pm

Just been through this. Here are two related posts I found for «linux mint flush dns cache».
viewtopic.php?t=190003
viewtopic.php?t=200955

LM 18.3 has cache-size=0, removing the need to flush the cache in a standard setup. You also have to check /etc/hosts for a permanent setting. Your router can have a cache that you can flush with a reboot or equivalent. In my case, it was the ISP caching DNS for more 24 hours or more.

Here is a tip. When you move from one IP address to another, you can stop the old server for a few seconds, perform an nslookup or equivalent, then switch the old server back on. The lookup will access the cache, find the IP address is invalid, and force a refresh of that entry in the cache. This worked for the entry stuck in my IPS’s cache.

Re: Flush DNS

Post by bob466 » Wed Apr 04, 2018 5:38 am

Re: Flush DNS

Post by Florian Schmidt » Sun Apr 26, 2020 12:44 am

This thread is a little old, but for me it keeps the first hit on google.

In current mint 19.3 (Tricia) you use:

Re: Flush DNS

Post by Pierre » Sun Apr 26, 2020 2:11 am

This thread is a little old, but for me it keeps the first hit on google.

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