Add a user: useradd username (only root users)
Set a password for the user to add: passwd username
Follow the prompts to set a password
See all users: cat / etc / passwd
To delete a user: userdel -r spark -r says to add a user and the user's home directory are deleted, without the user will only be deleted from the configuration file but the user's home directory and data are still
Need to exit before deleting command: exit
Tom add a user, provided it belongs to the group users, and add annotations
Step by step to complete: useradd tom
usemod -g users tom
usemod -c "hr tom" tom
One step: useradd -g users -c "hr tom" tom
Tom set a user's password: passwd tom
Modify the user's login name is tom tomcat: usermod -l tomcat tom
The tomcat added to the group sys and root: usermod -G sys, root tomcat
View tomcat group information: groups tomcat
Add a group called america's: groupadd america
Jerry america will add to the group: usermod -g america jerry
The tomcat user is removed from the root and group sys Group: gpasswd -d tomcat root
gpasswd -d tomcat sys
The group name changed to america am: aroupmod -n am america
Sudo permissions configured for the user (sudo: ordinary users is being used in this section in order to obtain administrator privileges to run, when this command is executed completely automatically return to normal user privileges)
vi / etc / sudoers (need to be configured before use sudo): editor as root
In the following location of the file, you can add a line to hadoop
root ALL=(ALL) ALL
hadoop ALL=(ALL) ALL
Then, hadoop sudo user can use to perform system-level instructions: [hadoop @ shizhan ~] $ sudo useradd huangxiaoming