Linux User Management

1: System User files

/ETC/PASSWD is used to save the file of the system user's user settings. To view the contents of a system User file:

cat/etc/passwd

2: View user password file

The file used to save the user's password is/etc/shadow, because Shadow is also a shadow, so someone calls it a shadow file and looks at the contents of the shadow file:

Cat/etc/shadow

3: Add user command

useradd [option] Tannengcai (Create a user with an account named Tannengcai)

The common options (option) are:

G: Specify the user group for the new user Useradd-g Group user (group with the Users group for the new user added using the option specified)

S: Specifies the shell used by the new user; Useradd-s/bin/ksh User (the default shell for user added with options specified is/bin/ksh)

4: Set User password command

When adding a user must remember to set the user password, or others can not login (no settings, password is messy)

passwd User (set user's password command)

5: Delete User command

Userdel [option] Username

The common option [option] is only r, and the function of this option is to delete the user in conjunction with the user's home directory and mail files, such as:

Userdel-r Tannengcai

If you forget to add the option r when deleting the user, you can only delete the user information, the user's home directory and mail files will also be retained, if you want to delete again, please use:

rm-rf/home/tannengcai/

6: User Management commands

usermod [option] Username

Common options [option] are:

L: Lock users, that is, prevent users from logging into the system

U: Unlock

E: Specify user Expiration Time

F: Refers to the buffer time after the user expires, that is, the number of days to log in after expiration

D: Specify a new home directory for the user

M: To specify a new home directory for users, move all files in the original home directory

S: Modify the user's default shell

Usage examples:

USER-L username;

User-u username;

USER-E username;

USER-F username;

user-d/file/user/home/user username;

user-d/file/user/home/user username-m username;

Linux User Management