Useful Commands

• Top provides a dynamic real-time view of a running system.
  • PID (Process ID): The unique identifier for each process.
  • USER: The user or owner of the process.
  • PR (Priority): The priority of the process.
  • NI (Nice Value): The “niceness” of the process.
  • VIRT (Virtual Memory): The total virtual memory used by the process.
  • RES (Resident Memory): The non-swapped physical memory used by the process.
  • SHR (Shared Memory): The shared memory used by the process.
  • S (%CPU): The percentage of CPU usage by the process.
  • MEM (%MEM): The percentage of RAM usage by the process.
  • TIME+: The total CPU time the process has used since it started.
  • COMMAND: The command or program associated with the process
• A useful combo for redirecting the non-commented lines in a file, to another file:
  • grep -Ev '^($|#)' <path-to-file> | wc -l > <path-to-new-file>
• Getent displays entries from databases supported by the Name Service Switch libraries, which are configured in /etc/nsswitch.conf.
  • getent hosts
  • getent group
  • getent passwd
  • getent shadow
  • getent services