Chapter 15: Working with the Command Line Interface (A+ Study Notes)

A+

Study Notebook

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You can find my complete study notes in Google Docs format below: https://docs.google.com/document/d/1zcKLWfsns1tqzmXtVRJbcd9NqfaEcjifgIo-oJIbEgc/edit?usp=sharing

References:
M. MEYERS, 2019.  CompTIA A+ All-in-One Exam Guide. 10th ed.

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Chapter 15: Working with the Command Line Interface

Command-Line Interpreter = Shell

Windows `Command` vs macOS/Linux `bash` (e.g. Unix based `Terminal`) 

macOS/Linux shell types:  

            Z shell (zsh)

            Korn shell (ksh)

            C shell (csh)

            Etc.

Windows alternative:

            PowerShell

“Run as administrator” (Windows) vs `su /sudo` (macOS/ Linux)

“/” forward slash on macOS/Linux

“\” backslash on Windows

• Command Line Interpreter (CLI)

• `hostname` (Windows/Mac/Linux)
• `dir` (windows) vs `ls` (mac)

• `dir /p` vs `ls | more` (pauses in between when searching large directories: hit spacebar/ enter to go to the next page)
• `ls -l`  (macOS / Linux - display long listing & permissions about all files)
• `cd`
• `cd ..` (to go back)   
• `cd ~` (Linux / Mac - automatically puts you back into home directory)
• `pwd` (Linux/Mac - show current directory) 

• `md` (Windows - create directory) or `mkdir` (Windows/Mac/ Linux - create new folder)
• `rmdir /` (delete folder)
• `rd /s` (Windows - delete folder) or `del` (delete file)
• `rm -r` (Mac/Linux - delete folder)
  
• `copy filename location` (Windows)
• `cp` | `mv` (Mac/Linux - copy | move )
• `xcopy` (Window - can work with multiple directories)
• `robocopy` (Windows - Robust File copy - fully replicates the structure of the destination system and deleting anything on that system that wasn’t part of copy)

• `/mir` - copy source and make the destination mirror it 
• Copy even if admin didn’t give you access to that file
  
  
• `chkdsk` (check disk)
• `chkdsk -f` (check disk on boot and attempt to fix file system-related errors)
• `chkdsk -r` (locate and repair bad sectors)
• `gpupdate` (Windows - force workstation to update to new policies)
• `gpresult` (Windows - quick overview of all security policies) 
• `sfc /scannow` (system file checker) - repair critical windows files 
• `dism` (windows) (helps fix Windows Corruption Errors) 
• `diskpart` (windows)
• `format` | `quickformat`

• `ifconfig` (View and change the settings for your network connections)

• eth0, eth1, en0, en1, and so on: wired Ethernet NICs

• wlan0, wlan1, and so on: wireless 802.11 NICs

• lo: loopback

·       `Ifconfig eth0 down`(to Disable a NIC on eth0)

·       `ifconfig wlan0 192.168.4.15` (temporarily change IP of wlan NIC to e.g.: 192.168.4.15)

·       `iwconfig` (get wifi NIC info) 

·       `sudo iwconfig wlan0 essid “AnotherSSID”` (change network SSID)

·       `ps` (process running)

·       `ps aux` 

A = processes for all users

U = shows process owner

X = process not attached to a terminal

• USER: Who is running this process

• PID: The process ID number assigned to the process

• %CPU: What percentage of CPU power this process is using

• %MEM: What percentage of memory this process is using

• VSZ: Total paged memory in kilobytes

• RSS: Total physical memory in kilobytes

• TTY: The terminal that is taking the process’s output

• STAT: S = waiting, R = running, l = multithreaded, + = foreground process

• START: When the process was started

• TIME: Length of time process has been running

• COMMAND: Name of the executable that created this process

·       `ps | less`

·       `ps | more`

·       `kill processnumber` (to kill a process)

·       `grep` (to filter stuff)

·       `apt-get/ APT`(Advanced Packaging Tool) vs `RPM` (Red Hat Package Manager)

·       `sudo apt-get update` (to update all package index)

·       `sudo apt-get install appname` (to install apps)

·       `sudo apt-get upgrade appname` (to update the app)

·       `sudo apt-get upgrade` (update all apps on the system)

·       `vi`

·       `vi newfile` (create new text file)

·       Command mode (default) vs insert mode (click `i` to get into it) 

·       `ZZ` (to save and quit)

·       `dd` (create exact bit-by-bit image of any form of block storage)

·       `dd if=path of=destinationpath` (to create a copy)

·       `dd if=/dev/urandom of=/dev/sdb` (Wiping a disk)

·       /dev/urandom - random number generator on Linux

·       `passwd` (change password)

·       `icacls fodlername /grant username` (Windows - to grant file/folder permissions to another user)

·       `chmod` (Linux/ macOS) - change permissions

·       `chown` (Linux /macOS) - change ownership

• Scripting

• Common scripting languages:

• .bat - batch file 
• PowerShell (.ps1) 
• Shell script (.sh)
• Python (.py)
• JavaScript (.js)
• VisualBasic Script (.vbs)
• Variables, Integers, Strings
• Conditional (if/else)
• Loops (for/while)

`cows = 0

while cows < 4;

            print (“moo”)

            cows = cows + 1`

Loop until 4 is reached. 

·       Comments 

·       Environmental Variables - system wide variables