Networking

scp — a utility for copying files over SSH using the SSH protocol. It works from the terminal, requires no extra server setup — just a running sshd and working authentication. In an era of rsync and bat, SCP survives as a simple tool for one-off …

Note All commands were verified on Debian/Ubuntu with the nftables package and on RHEL/CentOS 8+. On older systems you may need apt install nftables or yum install nftables. nftables replaced iptables, but documentation for a basic rule set is often …

Why You Need a Bastion and Where It Lives A bastion is the single entry point into a private network segment. Instead of exposing SSH on every server to the internet, you funnel traffic through one hardened host with a strict access policy. Typical …

Sometimes a server sits in a private network with no public IP. The only entry point is a bastion host with a public address. Typing ssh -J user@bastion user@private every time gets old fast. Here’s how to configure everything in ~/.ssh/config so you …

Warning Before changing nftables, make sure you have physical or console access to the server. A misconfigured input chain can block SSH and lock you out. nftables replaced iptables in the Linux kernel starting with version 3.13. If you’re still …

Sometimes you need to reach a Unix socket from a host where that socket doesn’t physically exist. SSH tunnels won’t help — they only work with TCP ports. socat solves this: it opens a TCP listener and forwards connections to a Unix socket, and the …

DNS resolvers return the wrong address, clients don’t see updates, or it’s unclear which server is handling requests. dig (Domain Information Groper) is the standard CLI tool for DNS diagnostics. Works on Linux, macOS, and Windows via WSL. …