SAM ( midterm)

• Permission Groups

  • Owner
  • Group
  • All Users
• Permission Types

  • Read
  • Write
  • Execute
• Permission Commands

  • id
  • chmod
  • umask
  • su
  • sudo
  • chown
  • chgrp
  • passwd
• id


  Displays user identity
• chmod


  Allows you to modify the access rights of a file/directory
• umask


  Sets the default file permissions
• su


  Allows you to temporarily become the superuser
• sudo


  Allows you to execute a command as another user
• chown


  Allows you to change a file's ownership
• chgrp


  Allows you to change a file's group ownership
• passwd


  Allows you to change a user's password
• Common File Types

  • Regular file
  • Directory
  • Symbolic link
  • Character special file
  • Block special file
• File Mode


  Represents the permissions for a file or directory
• Octal Notation for chmod

  • 0 (---)
  • 1 (--x)
  • 2 (-w-)
  • 3 (-wx)
  • 4 (r--)
  • 5 (r-x)
  • 6 (rw-)
  • 7 (rwx)
• File Permission Values

  • 777 (rwxrwxrwx)
  • 755 (rwxr-xr-x)
  • 700 (rwx
• Directory Permission Values

  • 777 (rwxrwxrwx)
  • 755 (rwxr-xr-x)
  • 700 (rwx
• Symbolic Notation

  • u (the directory or file owner)
  • g (the group owner)
  • o (others)
  • a (short for all)
• Common Text-Based Editors Used in Linux

  1. emacs
  2. nano
  3. gedit
  4. vi
• emacs – can be customized and extended with different modes, enabling it to be used like IDE for programming language such as Java or C.
• nano – is a text editor designed for beginners.
• gedit – comes with the Gnome desktop. It only runs in the GUI environment
• vi – is a native editor found in all Linux and Unix systems. Most Linux distributions do not include real vi; rather, they include an enhanced replacement called vim (short for vi improved).
• Three (3) Modes of vi Editor

  1. command
  2. insert
  3. replace
• command - Keystrokes entered operate as command rather than characters entered into the document.
• insert - Any character entered is placed at the current cursor position
• replace - Any character entered replaces the character at the current cursor position.
• l or Right arrow - moves One character to the right
• h or Left arrow - moves One character to the left
• j or Down arrow - moves One line down
• k or Up arrow - moves One line up
• 0 - moves To the beginning of the current line
• ^ - moves To the first non-whitespace character on the current line
• $ - moves To the end of the current line
• w - moves To the beginning of the next word or punctuation character
• W - moves To the beginning of the next word, ignoring punctuation characters
• Ctrl+f or Page Down - moves One page down
• Ctrl+b or Page Up One - moves page up
• numberG - moves To line number
• G - moves To the last line of the file
• The A command moves the cursor to the end of the line before starting insert mode.