Some Useful Commands on Linux

nproc - find out the number of cores ulimit - find and change shell resources (-n number of open files) apt list --installed | grep ssh - search installed packages apt search == apt-cache search some_package - search for a package by name and description apt-cache pkgnames curl - search for a package by name apt show curl - search from a local updated list ps -ef - displays a full list of all processes running on the system in standard (full-format) format htop - display information (like top) systemctl show - displays the parameters and status of the systemd system manager itself systemctl show nginx - displays a full list of the internal properties and settings of the nginx service pidof name - display the PID of the command/program name iptables (-L) - a standard tool for viewing, creating, and configuring a firewall. netstat - Shows detailed information about the computer's network activity (list of all connections, open (listening) ports, program names and their PIDs, connection status, network statistics, routing table (similar to route -n), multicast group membership, queue status). 0.0.0.0:22 - means listening on port 22 route -n - Displays the kernel routing table lsof -p <PID> - Shows all open objects accessed by a specific process lsof -i :80 - Find the process listening on a specific port (e.g., 80) lsof -u user1 :w !sudo tee % - Write data if vim was opened without sudo hostname - Displays the hostname (the computer's network name; it can also be accessed using a loopback or its own IP address)..