• While Unix-based OSs tend to take liberties and focused on ease of access, Linux does not
• most processes are automated requiring virtually no system administrator intervention
• User Account User identifiers are at 1000 or higher (unless a legacy system then it was 500)
  • User Accounts are assigned a User Group with the same name as the user
  • they contain a defined home directory usually /home and defined login shell
• System Account User Identifiers occur at the time of the system installation
  • are either below 100 or between 500-1000
  • no dedicated home directory or not under /home
  • no valid login shell with rare exceptions
• Service Account User Identifiers occur when a service is installed
  • they will not run as superuser
  • directories outside of /home
  • no valid login shell
  • UID/GID is above 1000 but not a standard or regular user account (nothing already assigned)
  • some UIDs are below 100 such as Apache Web Server on Fedora and Red Hat is UID/GID 48
• shell type can be changed using chsh command
• last command indicates the last time users have logged into the system

(https://www.geeksforgeeks.org/linux-unix/last-command-in-linux-with-examples/)

**Make sure to look it over to understand what last will provide when looking at when a user last logged in

• id command provides user id, primary group, and any additional GIDs
• lastb command provides a list of all bad login attempts
• w command includes
  • current time and how long the system has been up
  • how many users are connected
  • load averages for 1, 5, and 15 minutes
• In previous sections, we have already discussed how sudo elevates privilege and su switches user, but if you would like more details, see page 354

As a review:

• /etc/passwd - stores basic user information including UID, GID, home directory, shell
• /etc/group - stores information about all user groups
• /etc/shadow - user passwords stored via hash
  • contains information on last change, min password age, max password age, warn inactive, and expiration date
  • password is a one way hash with salt
  • !! will disable an account and ! disables an account with prior hash function/salt