Root File Structure

• bin – binary executables
• home – users home directory
• proc – processes
• dev – devices
• lib – 32 bit libraries (shared files aka dll)
• lib64 – 64 bit libraries (shared files aka dll)
• opt – optional software
• etc – configuration files

Hardware Abstraction Layer Protects the Kernel

Terminal aka Shell – Command Line Interface

When you launch a program, a virtual environment is spawned and rules are applied to protect the Kernel

Terminal Commands

• sh : the command name of the Bourne shell, the standard command language interpreter of Unix and many Unix-like operating systems, including Linux.
• bash : a Unix shell and command language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell.
• exit – close current instance.
• ls : lists all files in the directory that match the name. If name is left blank, it will list all of the files in the directory.
  • $ ls [options] [file|dir]
  • -l : Displays the long format listing.
• cd $ cd [directory]
  • Change to home directory (determined by $HOME environment variable):
    • $ cd
  • Also change to home directory:
    • $ cd ~
  • Change to root directory:
    • $ cd /
  • Change to parent directory:
    • $ cd ..
  • Change to subdirectory Documents:
    • $ cd Documents
  • Change to subdirectory Documents/Books:
    • $ cd Documents/Books
  • Change to directory with absolute path /home/user/Desktop:
    • $ cd /home/user/Desktop
  • Change to directory name with white space – My Images:
    • $ cd My\ Images
    • $ cd “My Images”
    • $ cd ‘My Images’
• cat : command is used to display the content of text files and to combine several files to one file. The cat command does not accept directories.
  • $ cat [options] file1 [file2…]
  • cat -b : add line numbers to non blank lines
  • cat -n : add line numbers to all lines
  • cat -s : squeeze blank lines to one line
  • cat -E : show $ at the end of line
  • cat -T : show ^I instead of tabs
• cp : copy files and directories – $ cp [options] source dest
  
  • -a : archive files
  • -f : force copy by removing the destination file if needed
  • -i : interactive – ask before overwrite
  • -l : link files instead of copy
  • -L : follow symbolic links
  • -n : no file overwrite
  • -R : recursive copy (including hidden files)
  • -u : update – copy when source is newer than dest
  • -v : verbose – print informative messages
• mv : move files and directories – $ mv [options] source dest
  • -f : force move by overwriting destination file without prompt
  • -i : interactive prompt before overwrite
  • -u : update – move when source is newer than destination
  • -v : verbose – print source and destination files
  • man mv : help manual
• rm : remove file
  • $ rm [OPTION]… [FILE]…
  • -r, -R, –recursive : Remove directories and their contents recursively.
  • -f, –force : Ignore nonexistant files, and never prompt before removing.

Permissions

• r : Read
• w : Write
• x :
  • File: Execute
  • Directory: List Directory

• File permissions: -rwxrwxrwx
  • – file
  • 1st 3 rwx : Owner
  • 2nd 3 rwx : Group
  • 3rd 3 rwx : Others
• Directory Permissions: lrwxrwxrwx or drwxrwxrwx
  • l – link
  • d – directory
  • 1st 3 rwx – Owner
  • 2nd 3 rwx – Group
  • 3rd 3 rwx – Others
• Default File permissions: -rw-rw-r–

File and Folder Management

• directory – folders
• permissions are assigned to files and folders to determine who has access to it
• A directory has a different permissions structure than a file
• A directory needs execute permissions to be able to see the contents of the directory
• . (dot) : current relative path
• .. (dot dot) : current relative path one level up