Created by Ashish Shah J M Patel College

Created by Ashish Shah, J. M. Patel College of Commerce Administering Users and Groups UNIT – 6 CHAP - 2 1

Created by Ashish Shah, J. M. Patel College of Commerce ADMINISTERING USER ACCOUNTS � Administering users and groups, or, more precisely, administering user and group accounts, is a fundamental Linux system administration activity. � Ordinarily, most people understand user accounts as accounts tied to a particular physical user. 2

Created by Ashish Shah, J. M. Patel College of Commerce ADMINISTERING USER ACCOUNTS � Other than this distinction between real and logical user accounts, there are few substantive differences between actual and logical users. In particular, both actual and logical have user identification numbers (UIDs), numeric values that the kernel and many applications use instead of the account name. � Ordinarily, each user account has a unique UID (on a given system), but this is not strictly required 3

Created by Ashish Shah, J. M. Patel College of Commerce WORKING WITH USER ACCOUNTS Table below lists the commands for adding, modifying, and deleting user accounts. You use the following commands most often: ■■ useradd — Create user login accounts ■■ userdel — Delete user login accounts ■■ usermod — Modify user login accounts ■■ passwd — Set or change account passwords ■■ chsh— Set or change a user’s default shell ■■ chage — Modify password expiration information The User Database Files To understand the following discussion, you need to know the format of the user database files, /etc/passwd and /etc/shadow. Each line in both files consists of colon-separated fields, one line per user. The format of the password file, /etc/passwd, is: username: password: 4

Created by Ashish Shah, J. M. Patel College of Commerce ADMINISTERING USERS AND GROUPS WITH USER MANAGER � User Manager is a graphical tool for administering user and group accounts. � To use it, you must be logged in as root or otherwise have root access. To start User Manager, click Main Menu ➪ System Settings ➪ Users and Groups. � You can start from a command line using the command system-config-users in a terminal window. 5

Created by Ashish Shah, J. M. Patel College of Commerce 6