#linux

A box is slow or swapping. Work through it step by step: measure, find the offender, kill it if needed, then check whether a service — not a one-off process — is the real cause via systemctl and journalctl.

Every way to install software on Ubuntu: a downloaded .deb (apt / dpkg / gdebi), official & vendor APT repos, PPA, Snap, Flatpak, AppImage, tarballs, source builds and language managers plus how to inspect, fix and remove packages.

Install Docker Engine and the Compose plugin on Ubuntu from Docker's official apt repository, then run docker without sudo.

Bootstrap a real multi-node cluster on Ubuntu VMs with kubeadm and containerd: prepare nodes, init the control plane, install a CNI, join workers.

Changes a file or directory's read/write/execute permissions — for the owner, group, and everyone else.

Changes which user and group own a file or directory — usually needs sudo unless it's already yours.

Makes HTTP (and other protocol) requests from the command line — for testing an API, downloading a file, or debugging a service.

df reports free space per filesystem; du reports how much space a directory tree is actually using.

Walks a directory tree looking for files matching name, type, size, or age — and can run a command on every match.

Searches text for lines matching a pattern — files, or anything piped in.

Sends a signal to a process — usually asking it to terminate, gracefully or not.

ps takes a snapshot of running processes; top (or htop) watches them live, sorted by resource usage.