What does flushdns mean? Detailed explanation of the principle and function of flushdns

in the daily network access, you may have encountered a clear URL has been updated but can not be opened normally, or the same website in other devices can access their own devices but error, which is most likely related to DNS cache. And flushdns is the key to solve this kind of problem operation, this article from the definition, principle, operation method to the actual role, all-round explanation of flushdns related knowledge, help you easily deal with all kinds of DNS cache caused by network failure.

What does flushdns mean?

understand the role of flushdns, it is first necessary to clarify its basic definition and its association with DNS cache.

1, basic definition of flushdns

flushdns is a network command, the main function is to clear the local DNS cache data of the device. DNS cache is the corresponding record of the domain name and Internet Protocol Address temporarily stored by the device in order to improve the network access speed. When the flushdns command is executed, these temporarily stored records will be cleared, and the device needs to re-request the latest domain name resolution data to the DNS server.

2, flushdns and DNS cache association

DNS cache can reduce the time of repeated resolution and improve access efficiency, when the Internet Protocol Address of the website is updated, the old cache records will cause the device to fail to access the latest website server. At this time, flushdns has become the core operation of resetting the DNS cache.

2. What is the core working principle of flushdns?

understand how flushdns works can help you understand more clearly why it can solve DNS caching problems and its role in the network access process.

1, DNS cache storage logic

when you visit a domain name for the first time, the device will send a resolution request to the DNS server, and after obtaining the Internet Protocol Address corresponding to the domain name, this group of correspondence will be stored in the local cache. The cache has a certain valid period. Access to the same domain name within the valid period, the device will directly call the data in the cache, without requesting the DNS server again, which is also the premise logic that flushdns needs to intervene.

2, flushdns execution logic

when the flushdns command is executed, the system will directly access the storage directory of the local DNS cache and delete all the corresponding records of the domain name and IP, which is equivalent to resetting the local DNS resolution record database. At this time, when the device accesses the domain name again, it will restart the DNS resolution request and obtain the latest correspondence from the DNS server to solve the access exception caused by the old cache.

How do different systems implement flushdns?

flushdns operation steps are slightly different in different operating systems, the following is a detailed introduction to the execution method under Windows, Mac and Linux systems for you.

1, Windows system execution flushdns

first press the Win + R key combination to open the run window, enter cmd and press Enter to open the command prompt, enter ipconfig /flushdns in the command prompt window, after pressing the Enter key, the window will prompt "successfully refreshed DNS resolution cache", which means that the flushdns operation has been completed. It should be noted that some Windows systems need to open the command prompt as an administrator to execute this command.

2, Mac system execution flushdns

different versions of Mac system commands are slightly different. For Ventura and above, open the end point application in the startup console, enter sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder, press Enter and enter the administrator password to complete the flushdns operation. For older versions of the system, you can directly enter sudo killall -HUP mDNSResponder to perform cache cleanup.

3, Linux system implementation flushdns

Linux system according to the use of different services, flushdns command is also different, if you are using the nscd service, enter sudo /etc/init.d/nscd restart command to restart the service to clear the cache; if you are using the systemd-resolved service, enter sudo systemd-resolve --flush-caches command, after execution to complete the flushdns operation.

What are the practical functions of flushdns?

In addition to solving the basic DNS cache expiration problem, flushdns has many practical application scenarios that can help you solve a variety of network access failures.

1, solve the problem of abnormal website access

when the website server replacement results in Internet Protocol Address change, the local cache of old IP records will make the device access to the server failure, can not open the website, page loading error and other issues, then perform flushdns to clear the old cache, the device can get the latest Internet Protocol Address, restore normal website access.

2, improve the security of network access

some phishing websites will point the regular domain name to the malicious Internet Protocol Address by tampering with the DNS cache, so that users can visit the phishing website by mistake. Executing flushdns can clear the tampered cache records, let the device re-request the resolution data to the regular DNS server, avoid falling into the phishing trap, and improve the security of network access.

3, test website analysis effect

after the website domain name resolution configuration is completed, in order to test whether the resolution is effective, flushdns can be executed to clear the local old cache records, and then re-visit the website.

sum up, flushdns is the core command to clear the local DNS cache. From the basic definition, working principle to the operation method of different systems, to practical application scenarios, it is the key operation to solve the problems related to DNS cache. Mastering the use of flushdns can not only quickly solve the problem of abnormal website access, but also improve the security of network access and help test the effect of domain name resolution. It is an indispensable practical skill in daily network maintenance.