About systemd Units

• Units are the objects that systemd knows how to manage.
• These are basically a standardized representation of system resources that can be managed by systemd
• Each unit is configured by a unit file
• Here's are some of systemd units:
  • .service: A service unit describes how to manage a service or …

About systemd

• systemd is a software suite that provides an array of system components for linux
• The primary component is a "system and service manager" – an init system used to bootstrap user space and manage user processes.
• It also provides replacements for various daemons and utilities, including: …

About System Calls

• Some operations that are executed by a process involve just the CPU and the memory.
• Mathematical computations and logical decisiones are good examples of these.
• But sometimes, the process needs to do other things, that it cannot do alone.
  For example:
  • interract with the computer hardware (e.g …

Traditional creation of programs

• This is also called static linking
• The old way of creating programs was by writing multiple source files (text files with program code), then translating each one (called compile), thus creating object files.
  The, link these files to create an executable file, that can be run: …

What is a process

• A process is an instance of an executing program.
• A program is a file containing a range of information that describes how to construct a process at run time:
  • Machine-language instructions: These encode the algorithm of the program.
  • Data: The program file contains values used to initialize …

Linux Basics

• linux introduction

• linux links

• Running in VirtualBox

• trying out commands

• command types

• basic linux review questions

Linux Files

• file basics

• file permissions

• devices & mount

• hard & soft links

• linux files review questions

Processes …

About the linux directory tree

• Linux has a single directory tree, starting with the root directory
• Othe oerating systems use different methods to refer to the same information.
  Microsoft Windows for example, uses a single tree for each device. It uses letters to refer to thise devices.
  eg: a:\mydir\myfile.txt
  is a …

inodes

• The inode (index node) is a data structure in a Unix-style file system that describes a file-system object such as a file or a directory.
• Each inode stores the attributes and disk block locations of the object's data
• Since each file has a single inode, the inode number can be thought of the "physical …

About Permissions

Here's a long listing of a file I've created with the touch command:

1-rw-rw-r-- 1 osboxes osboxes    0 Jan  7 07:30 myfile

This is the explanation to the first field you see:

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  loading="lazy" …</picture></figure></p>

Use this post as a guide, to learn basic file commands.

List Files

• Use ls to just list file:

1ls

• Use long listing (ls -l) to do the same.
• List a specific file (let's say you have a file called "mydata"):

1ls mydata

• Long list that file:

1ls -l mydata

• List a directory that is not the current directory: …