User permission-related commands

Commands related to user permissions 1. Create groupadd test, modify groupmod-n test2 test, change the name to test2, delete groupdel test, view group groups root2, and perform user operations: -B: set the basic path as the user's login directory usermod-B/home root;-c comment on the user... -D: Set the user's logon directory usermod-d/home root;-D: Change The usermod-D-e to set the user's validity period usermod-e 2013-2-1;-f: After the user expires, make the password invalid usermod-f root;-g make the user belong to only a group of usermod-f www group2;-G make the user join a group of usermod-f www group1; -h help-k (skel_dir) to specify other skel directories (directories that store User Startup files)-k (key = value) -m automatically creates a login directory-l does not add users to the lastlog file-M does not automatically create a login directory-r creates a system account-o allows users to have the same UID-p for new users use the encrypted password; -s shell at login... -U specifies a UID for the new user;-Z deletes the user: userdel www; views the user: w/who to view its user name: whoami to view the individual user information: finger root, id root; view User Logon records: last and lastb (successful and unsuccessful)