Linux

Lists files with permissions, owner, human-readable size, and includes hidden files.

Finds files matching a name pattern, modified more than 7 days ago.

Copies a directory recursively.

Deletes a directory and everything in it, without confirmation. No undo, no trash — verify the path before running this.

Creates a gzip-compressed tarball of a directory.

Extracts a gzip-compressed tarball into the current directory.

Sets owner read/write/execute, group and others read/execute — the standard mode for an executable script others need to run but not modify.

Changes a file's owning user and group.

Applies a permission change recursively through a directory tree — combine with a mode, e.g. chmod -R 644 DIR_NAME.

Lists every process on the system with CPU/memory usage, owning user, and command line.

Filters the process list to a specific name.

Live, auto-refreshing view of processes sorted by CPU usage.

Sends SIGTERM to a process, requesting graceful shutdown.

Sends SIGKILL — terminates immediately with no chance for the process to clean up, close files, or flush buffers. Use only after a plain kill hasn't worked.

Runs a command immune to hangup signals and detached into the background, so it survives the terminal session closing.

Shows live per-process CPU and memory usage, plus system-wide load average.

Shows total, used, and free memory and swap in megabytes.

Shows how long the system has been up and the 1/5/15-minute load averages.

Prints the number of available CPU cores — useful context for interpreting a load average.

Shows disk space usage per mounted filesystem in human-readable units.

Shows the disk usage of each item in the current directory, summarized rather than listing every file inside.

Finds the 10 largest items under a directory — the fastest way to locate what's actually eating disk space.

Lists open files with a link count of zero — a deleted-but-still-open file, which keeps holding disk space until the process closes it.

Shows network interfaces and their assigned IP addresses.

Lists listening TCP/UDP sockets with the owning process — the modern replacement for netstat.

Fetches only the response headers, for a quick check that a service is up and what it's returning.

Sends 4 ICMP echo requests to test basic reachability.

Shows the network hops a packet takes to reach a host — useful for isolating where latency or a drop is happening.

Opens an interactive SSH session.

Connects using a specific private key instead of the default identity.

Copies a local file to a remote host over SSH.

Generates a new SSH keypair using the modern ed25519 algorithm.

Shows whether a service is running, its recent log lines, and its enabled/disabled state.

Starts a service immediately.

Stops and starts a service in one step — the usual way to apply a config change.

Configures a service to start automatically on boot, without starting it now.

Reloads systemd's unit files after editing one — required before a changed unit file takes effect.

Shows the systemd journal for a specific service.

Streams a service's journal live, like tail -f.

Filters the journal to a relative time window across all units.

Streams a plain log file live. Use /var/log/messages on RHEL-family distributions instead.

Refreshes the package index, then installs a package (Debian/Ubuntu).

Installs a package on RHEL/CentOS-family distributions.

Checks whether a package is installed and its version (Debian/Ubuntu).

Finds files by name across the filesystem, discarding permission-denied noise.

Searches recursively for a pattern, printing matching line numbers.

Counts matching lines instead of printing them.

Opens the current user's crontab for editing.

Lists the current user's scheduled cron jobs.