Linux Concepts for Beginners

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Linux Concepts for Beginners

The linux kernel is the heart of the operating system. It controls excess to the computer and its files, allocates resources amongst the various activities taking place within the computer, maintains the file system and manages the computer memory.

A system administrator can adjust the system's operating characteristics by configuring the kernel. Configuring the kernel chiefly involes specifying whether certain features of the system could be included.

To view all the programs that are currently running (i.e., executing) on your linux machine, use the command ps -ef

"ps" stands for process and it is name of the command.
It supports 2 options: e and f
  1. e => Produce information about every process ( including those working in the backgrounds like daemons)
  2. f => Produce a full listing of information as follows:
    • UID => The user associated with the process
    • PID => The process number
    • PPID => The process number of the process's parent
    • C => The processor utilization, for scheduling processes
    • STIME => The staring time of a process. A process staartedmore than a aday ago is given in months and days
    • TTY => The controlling terminal for the process
    • TIME => The cumulative execution time for the process in minutes and seconds of central processor time
    • COMMAND => The command being executed by the process

Signals

A signal notifies a process of an abnormal external event such as disconnection of the terminal.
Every process that has completed its execution sends an exit status to the console to excess the exit statusof the previously run command use the following line of code.

$?

It returns either 0 or any other integer. If the output is zero it implies that the process is executed successfully without any error.
It it returns a value other than zero then the programme has returned and has been stopped by an error.

Process group

A process group is a set of processes that can be signalled together.

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