{"id":5300,"date":"2021-09-16T14:56:57","date_gmt":"2021-09-16T14:56:57","guid":{"rendered":"https:\/\/fisthost.com\/blog\/?p=5300"},"modified":"2021-09-16T14:57:01","modified_gmt":"2021-09-16T14:57:01","slug":"flush-dns-server-cache-on-windows","status":"publish","type":"post","link":"https:\/\/fisthost.com\/blog\/flush-dns-server-cache-on-windows\/","title":{"rendered":"Flush DNS Server Cache on Windows"},"content":{"rendered":"\n

When you type a website into your address bar like “Fisthost.com” your computer doesn’t actually know where to go on its own. Instead, it looks that address up on a Domain Name System (DNS) server, which matches it with an\u00a0IP address\u00a0for your computer to visit.<\/p>\n\n\n\n

Anyone who moves about on the internet leaves a lot of traces \u2013 even inexperienced browser users probably know this by now. Website operators use technology such as cookies or JavaScript applications to record the behavior of visitors<\/strong>. The data obtained here is used to optimize the website and personalize the content without users actively disclosing personal details<\/strong>. Many users increasingly rely on ad and JavaScript blockers and proxies<\/strong> or delete history and cookies to put an end to data collection and protect their own privacy<\/strong>.<\/p>\n\n\n\n

However, very few users are aware that the\u00a0operating system also saves information<\/strong>\u00a0about surf behavior: for example, the automatically generated DNS cache contains temporary entries about all visited websites. The following sections explain exactly what this\u00a0cache<\/strong>\u00a0is all about and why there are several reasons to\u00a0delete the DNS cache regularly<\/strong>.<\/p>\n\n\n\n

What is the DNS cache?<\/h2>\n\n\n\n

DNS servers\u00a0are used to convert domain names such as\u00a0www.example.com\u00a0<\/em>into numerical addresses<\/strong>\u00a0that can be processed by computer systems. These \u201cname servers<\/strong>\u201d are contacted by default via the browser each time the corresponding projects are accessed, which slightly increases their loading time and can also lead to a DNS server\u00a0overload<\/strong>\u00a0in the case of a\u00a0high number of visitors<\/strong>. Error messages like \u201cDNS Server Not Responding\u201d are a common and despised consequence.<\/p>\n\n\n\n

For this reason, operating systems like Windows and macOS attach their own cache for\u00a0called and resolved addresses<\/strong>\u00a0\u2013 the DNS caches. These save all information that\u2019s relevant for name resolution, each with an entry known as\u00a0TTL (time to live)<\/strong>\u00a0where data remains valid for a given time. Within this time, corresponding queries are\u00a0answered directly from the cache\u00a0without requiring a detour to the DNS server.<\/p>\n\n\n\n

How to flush DNS<\/h2>\n\n\n\n

As a user of Windows 7, you can run a DNS flush via the command prompt<\/strong>. To use this, click on the Windows home button and type \u201ccmd\u201d into the search bar. Then start the command line tool by clicking or pressing enter.<\/p>\n\n\n\n

Enter the following command<\/strong>:<\/p>\n\n\n\n

ipconfig \/flushdns<\/code><\/pre>\n\n\n\n
When you press enter, Windows clears the DNS cache. You\u2019ll receive the following message confirming that the cache was successfully flushed.<\/p>\n\n\n\n
\"\"<\/figure><\/div>\n\n\n\n
Run a DNS flush on Linux: how it works<\/h2>\n\n\n\n
Linux systems don\u2019t have a DNS cache by default. The different distributions only offer a function to store DNS information locally <\/strong>with the use of appropriate applications like nscd (n<\/strong>ame s<\/strong>ervice c<\/strong>aching d<\/strong>aemon), pdnsd, dns-clean, or dnsmasq. If you use one of these services for caching, you have to control it from the terminal in order to clear the cache.<\/p>\n\n\n\n
For pdnsd<\/strong>, there\u2019s a concrete clear command<\/strong>:<\/p>\n\n\n\n
sudo pdnsd-ctl empty-cache<\/code><\/pre>\n\n\n\n
To clear the DNS cache from dnsmasq<\/strong>, dns-clean<\/strong>, or ncsd<\/strong>, though, you need to completely restart<\/strong> the respective service:<\/p>\n\n\n\n
sudo \/etc\/init.d\/dnsmasq restart\nsudo \/etc\/init.d\/nscd restart<\/code><\/pre>\n\n\n\n
sudo \/etc\/init.d\/dns-clean restart<\/code><\/pre>\n\n\n\n
<\/a><\/p>\n\n\n\n
\"\"<\/figure><\/div>\n\n\n\n
How to flush DNS on Mac<\/h2>\n\n\n\n
Like Windows, macOS has an integrated DNS cache that automatically collects DNS information and so should be cleared regularly. As opposed to the Microsoft systems, though, the command for resetting the cache<\/strong> varies from version to version. What you need to enter into the terminal<\/strong> to set the DNS register back to zero depends on the edition that you\u2019re working with:<\/p>\n\n\n\n
macOS 10.12.0 (Sierra):<\/strong><\/p>\n\n\n\n
sudo killall -HUP mDNSResponder<\/code><\/pre>\n\n\n\n
OS X 10.10.4 (Yosemite) and 10.11.0 (El Capitan):<\/strong><\/p>\n\n\n\n
sudo dscacheutil -flushcache;\nsudo killall -HUP mDNSResponder<\/code><\/pre>\n\n\n\n
OS X 10.10.1 to 10.10.3 (Yosemite):<\/strong><\/p>\n\n\n\n
sudo discoveryutil mdnsflushcache\nsudo discoveryutil udnsflushcaches<\/code><\/pre>\n\n\n\n
OS X 10.9.0 (Mavericks):<\/strong><\/p>\n\n\n\n
sudo dscacheutil -flushcache;\nsudo killall -HUP mDNSResponder<\/code><\/pre>\n\n\n\n
Google Chrome browser<\/h2>\n\n\n\n
The Google Chrome web browser maintains its own internal DNS cache. To clear it, follow these steps:<\/p>\n\n\n\n
  1. Start Google Chrome.<\/li>
  2. In the address bar, type chrome:\/\/net-internals\/#dns. Google Chrome displays a list of hosts in its internal DNS cache.<\/li>
  3. Click Clear host cache<\/strong>.<\/li>
  4. In the address bar, type chrome:\/\/net-internals\/#sockets.<\/li>
  5. Click Close idle sockets<\/strong>, and then click Flush socket pools<\/strong>.<\/li><\/ol>\n    
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