When two or more installed programs provide the same command name, the system needs a way to decide which one runs by default. The update-alternatives command on Ubuntu, Debian, and their derivatives manages this through symbolic links in /etc/alternatives. This guide covers how...

DNS cache is a temporary database your OS and browser build as you browse. Each time you visit a website, the domain-to-IP mapping is saved locally, cutting out the round trip to a remote DNS server on repeat visits. Stale entries are the most common reason to flush the DNS cache: a server moves to a new IP, but your OS or browser still routes to the old address. This guide covers how to clear the DNS cache on Windows, Linux, and macOS, and how to flush the separate cache stored inside Chrome and Firefox. Flush DNS Cache on Windows The command is the same on Windows 10, Windows 11, and earlier supported releases. Open Command Prompt with administrator privileges. Type cmd in the Windows search bar, right-click Command Prompt, and select Run as administrator. Run the flush command: A successful run prints: ipconfig /flushdns clears all entries from the Windows DNS Resolver Cache. The OS makes fresh DNS queries on the next domain lookup. Clear the DNS Cache on Linux Linux does not cache DNS entries at the OS level by default. DNS caching only happens when a dedicated service is installed and running. Before flushing, check which caching service is active on your system. systemd-resolved – the default resolver on Ubuntu, Fedora, and most modern desktop distributions. Check whether it is running: If the output is active, flush the cache with: The command produces no output on success. Older guides show sudo systemd-resolve --flush-caches – that command is deprecated on modern systems and replaced by resolvectl. DNSMasq – a lightweight caching nameserver common on embedded and router-style Linux systems. Restart the service to clear its cache: Nscd – the Name Service Cache Daemon, found on older Red Hat and CentOS systems: Clear DNS Cache on macOS and...

The free command in Linux gives you a quick summary of RAM and swap usage. It reads from /proc/meminfo and displays the data in a single table with one command. This guide covers how to use the free command in Linux and what each column in...

The rmmod command in Linux removes a loaded module from the running kernel. Because the kernel has a modular design, you can load and unload drivers and features on demand, without rebooting or recompiling anything. This guide covers how to use the rmmod command...

Using a strong, unique password for every account is one of the most effective security habits. A compromised password accounts for a large share of account breaches, and reusing passwords across services means one breach cascades into many. This guide...