Permissions: user management (add, delete, modify and check users), group management, permission management
User management: useradd, userdel, passwd, usermod, finger, id, chage
useradd [options] username: add user; userdel username: delete user options = -u UID , -g GID basic group, -G GID additional group, -s shell
passwd username(default=root) Enter=="Enter password
echo "password" | passwd --stdin username ==> Change the user's password to "password"
id username == "View the user's id
Rights management: 9 digits, 3 groups*3 digits
Group 1: file owner permissions
Group 2: Permissions for other group members in the group where the file owner belongs
Group 3: Other User Permissions
chmod o+(-)w filename: increase (decrease) w permissions for other users
chown group name: user name file name == "change the owner of the file to the corresponding user name under the group name
chmod g+w file: add w permission to group
chmod 666 (777) 1.txt adds w (all) permissions to all groups
chmod -R o+w directory name: add w permissions to all files in the directory