Команда useradd

Options:

-d home directory
-s starting program (shell)
-p password
-g (primary group assigned to the users)
-G (Other groups the user belongs to)
-m (Create the user's home directory

Example: To add a new user with

a primary group of users
a second group mgmt
starting shell /bin/bash
password of xxxx
home directory of roger
create home directory
a login name of roger

  useradd -gusers -Gmgmt -s/bin/shell -pxxxx -d/home/roger -m roger

top of page usermod - Modifying existing user

Options:

-d home directory
-s starting program (shell)
-p password
-g (primary group assigned to the users)
-G (Other groups the user belongs to)

Example: To add the group 'others' to the user roger

  usermod -Gothers roger

top of page userdel - Deleting a user

Options:

-r (remove home directory)

Example: To remove the user 'roger' and his home directory

  userdel -r roger

top of page

passwd - User's Password

Options:

user's name (Only required if you are root and want to change another user's password)

Example: To change the password for the account you are currently logged in as…

  passwd
  Enter existing password
  Enter new password
  Enter new password again (to validate)

Example: To change the password for the user 'roger' (only you are logged in as root)…

  passwd roger
  Enter existing password (can be either roger's password or root's password)
  Enter new password
  Enter new password again (to validate)

top of page Where user and group information stored

User names and primary groups are stored in /etc/passwd. This file can be directly edited using the 'vi' editor, although this is not recommended. Format of the file is…

User (name normally all lower case)
Password (encrypted - only contains the letter 'x')
User ID (a unique number of each user)
Primary Group ID
Comment (Normally the person's full name)
Home directory (normally /home/<user name>
Default shell (normally /bin/bash)

Each field is separated by a colon.

Passwords for each user are stored in /etc/shadow. This file should only be changed using the passwd command.

Group information is stored in /etc/group. This file can be directly edited using the 'vi' editor. Format of the file is…

Group name
Group password (hardly ever used)
Group ID
User names (separated by commas)

Each field is separated by a colon.

Default files

When a new user is created, the default files and directories that are created are stored in /etc/skel.

This directory can be modified to fit your needs. Modifications only effect new users and does not change anything for existing users.

top of page su - Switch User

To switch to another user, use the su command. This is most commonly used to switch to the root account.

  Example: To switch to root account...
  su
  Enter root's passwd

  Example: To switch to the user 'roger'...
  su roger
  Enter roger's or root's passwd

  To return to original user, enter exit

ssh

 useradd test

 passwd test

 usermod -Groot test

 visudo

   ## Allow root to run any commands anywhere
root    ALL=(ALL)       ALL

   ## Allow root to run any commands anywhere
root    ALL=(ALL)       ALL
test    ALL=(ALL)       ALL

Esc

:wq

 service sshd restart

 ssh test@127.0.0.1 -p 22

Система

linux, useradd