Category: Commands

Argument list too long, and filenames with spaces in them. xargs solves the first and creates the second unless you know the one flag that matters.

openssl has hundreds of subcommands and a manual page that assumes you already know cryptography. In practice there are six things people need, and each is one line.

Setting the clock is easy. The parts that bite are the two clocks in every machine, the difference between the system time zone and a user's, and what happens to…

Address already in use. Device or resource busy. Disk full but nothing is using the space. All three are the same question, and lsof answers it in one line.

The small commands that turn a log file into an answer. The count-and-rank pipeline, why uniq needs sorted input, when cut is the wrong tool, and the ones you forget…

Four tools for one job, and the choice matters. Which to use when, the flag that stops them deleting your original, using every CPU core, and how they hook into…

The full ip command: the object model, the two flags that make its output readable, ip route get, and the thing nobody tells you — none of your changes survive…

Filtering by unit, priority, boot and time; following logs live; the setting that decides whether yesterday's logs still exist; and how to stop the journal eating your disk.

Ctrl+R, history expansion, the readline editing keys worth learning, and the configuration that stops your history vanishing every time you close a terminal.

Creating accounts, adding someone to a group without wiping the groups they already had, password ageing with chage, and why locking an account beats deleting it.