Users, Processes, Permissions - and what's between them

Table of contents

• Introduction
  • Users
  • /etc/passwd
  • /etc/shadow
  • /etc/shadow (Cont.)
  • Groups
  • /etc/group
• Users, Groups and Files
  • The File's Owner User
• File Access Permissions
  • File Access Permissions - Who may access?
  • File Access Permissions - permission to do what?
  • Directory Access Permissions - permission to do what?
• Access Permission scenarios
  • 'read' Permission To Everyone On A File
  • 'execute' Permission To Everyone On A File in ~/bin
  • 'read' Permission To A Selected Group Of Users, On A File
  • 'read' Permission To Everyone except a Group of Users
• Users and Processes
  • Listing The Running Processes
  • Listing The Running Processes - Wider Format
  • Listing The Running Processes - Variations
• Controlling Processes
• Processes And Files
  • Which Processes Hold A File Open? (fuser)
  • Which Processes Hold A File Open? (fuser, Cont.)
  • Which Files Are Open By A Given Process? (lsof)
  • Which Files Are Open By A Given Process? (lsof, Cont.)
• Default Permissions For New Files
  • The umask Command
  • The Octal Notation Of Access Permissions
  • The Octal Notation Of Access Permissions (Cont.)
  • The Octal Notation And umask
• Special Access Permission Flags
  • The "Set User-ID" Flag
  • The "Set Group-ID" Flag
  • The "Sticky" Flag
• Symbolic Links
  • A Symbolic Link Example
  • Symbolic Links Semantics
  • Permissions And Symbolic Links
• What We Did NOT Cover Today

Originally written by guy keren