rsync copies files, but only the parts that changed. On the second run of a large transfer it sends almost nothing, which makes it the right tool for anything you…

Sooner or later you will SSH into a server, type vim or find yourself dropped into it by git commit, and discover that nothing you try makes it stop. This…

Linux does not have drive letters. Every filesystem is grafted onto a single tree at a mount point — a directory that becomes the doorway to that storage. Once that…

Every distribution installs software from repositories, and every distribution family uses a different command to do it. The concepts are nearly identical; only the spelling changes. This page puts the…

Both fetch things over HTTP. The difference in practice: curl is for talking to things — APIs, headers, authentication, sending data. wget is for taking things — downloading files, resuming,…

Linux has two kinds of link and they are not variations on the same idea — they work at different levels of the filesystem. Understanding the difference takes one paragraph…

“The network is broken” is four or five different problems wearing the same coat. These commands tell them apart: is there an address, is anything listening, can packets reach the…

Where grep finds lines and sed edits them, awk understands that a line has columns. That one idea is why it survives: any time your data has fields — log…

Sooner or later a Linux machine tells you No space left on device and something stops working. This page is the sequence for finding out what filled up and getting…

cron runs commands on a schedule. It has done so since the 1970s, it is on every Linux system, and it fails in a small number of extremely predictable ways…