Where Is the DNS Cache Stored on Server?
The Domain Name System (DNS) is a vital component of the internet that translates domain names into their corresponding IP addresses. Every time you visit a website, your computer or device queries a DNS server to obtain the IP address associated with the domain name you entered. To speed up this process and improve network performance, DNS caching is employed.
DNS caching involves storing previously resolved domain name and IP address pairs in a local cache. This allows subsequent requests for the same domain name to be resolved quickly, reducing the latency involved in querying external DNS servers.
Types of DNS Caches
There are two main types of DNS caches:
- Client-Side Caches: These caches are located on individual computers or devices. When you access a website, your browser may store the resolved IP address in its cache for a specified period of time, known as the Time-to-Live (TTL). This cache improves performance by eliminating the need to query a DNS server for every request to the same domain.
- Server-Side Caches: These caches are maintained by DNS servers themselves.
When a DNS server receives a query for a domain name, it checks its cache before forwarding the request to other servers. If it finds a matching record, it returns the cached IP address instead of performing additional lookups. Server-side caches significantly reduce response times and optimize network traffic.
The Location of Server-Side DNS Cache
The specific location where server-side DNS caches are stored depends on the type of server being used:
1. Windows Servers
In Windows Server environments, server-side DNS cache is stored in the DNS Client service. By default, the cache is located in the system’s memory and not written to disk.
This ensures high-speed access to cached data. However, it also means that the cache is volatile and will be lost if the server restarts.
If you need to view or manage the DNS cache on a Windows Server, you can use the dnscmd command-line tool or navigate to %SystemRoot%\System32\DNS\Cache directory where a temporary copy of the cache file may be stored.
2. Linux Servers
In Linux-based systems, server-side DNS caching is typically performed by a DNS resolver such as dnsmasq or Bind. The location of the cache file may vary depending on your specific configuration.
In most cases, you can find the DNS cache file at /var/cache/bind/. However, if you are using a different DNS resolver, refer to its documentation for accurate information about the location of the cache file.
3. macOS Servers
On macOS servers, server-side DNS caching is handled by mDNSResponder. The cache file for mDNSResponder can be found at /var/db/dnsCache.dns.
Clearing Server-Side DNS Cache
If you encounter issues with resolving domain names or need to update records manually, clearing the server-side DNS cache can be helpful. Here’s how you can clear it on different platforms:
– Clearing DNS Cache on Windows Server:
- Open Command Prompt with administrative privileges.
- Enter the command ipconfig /flushdns and press Enter.
– Clearing DNS Cache on Linux Server:
- Open a terminal.
- Enter the command sudo systemctl restart dnsmasq (if using dnsmasq) or sudo systemctl restart bind9 (if using Bind) and press Enter.
– Clearing DNS Cache on macOS Server:
- Open Terminal.
- Enter the command dscacheutil -flushcache and press Enter.
DNS caching is a crucial mechanism for improving network performance by reducing the time required to resolve domain names. The location of server-side DNS cache varies depending on the operating system and DNS resolver in use. Understanding where these caches are stored allows administrators to manage, troubleshoot, and clear them when necessary.
Note: It’s important to note that clearing server-side DNS cache may temporarily impact DNS resolution as it forces the server to query external DNS servers for every request until the cache repopulates with new entries.