UserManagement.md

User Management

All user manangment commands need to be executed with sudo, so the user who is creating/modifying users should be part of sudoers file.

Adding users

useradd is the command that let's you add users. However, this is a very basic command with limited options.

adduser is an enhanced command and generally used.

sudo add user <user_name>

Example

sudo add user wjohnson

when you create a user in Ubuntu with adduser command it will prompt you to enter password for the user. However in some distributinos like Centos, you may have to update password manually using the below commands

sudo passwd <user_name>

Example

sudo passwd wjohnson

Everytime a user account is created a group with the same name is also created by default. For example, if a user called testuser is created and a group with the name testuser is also created.

To create a user in a different group other than the one with his user name, use --ingroup option.

sudo adduser <newusername> --ingroup <groupname>

For instance if you would like to create a user with the username tester but not create a group with the same name and want him to be part of the group qa then use the below command:

sudo adduser tester --ingroup qa

To delete a user use the below commands

sudo userdel <user-name>

All the user details are stored in the file /etc/passwd. It is not recommended to edit these files, use usermod instead

User Groups

Groups are a way to organize users. Everyuser is part of a default group.

To create a group use the below command

sudo groupadd <group_name>

Example:

sudo groupadd tesers

To delete a user, use the below command

sudo groupdel <group_name>

Example:

sudo groupdel tesers

To see the groups to which a user belongs to use the groups command

The below command gives the list of groups to which the current user is part of

groups

To see the list of groups for another user, use the below command

groups <username>

For example if you're logged in as john but would like to see the groups of alice, use the below command:

groups alice

Information about all the groups is stored in the file /etc/group

Switching Users

su -- Switch user ; to login as a different user

su - <username>

For example if you're logged in as john but would like to switch to tu user alice, use the below command: [this assumes you know the password for the user alice]

su - alice

If you're a superuser, you need not know the password for the user you can sudo su

sudo su - alice

To logout from the session:

exit

Modfiy user attributes:

The command usermod is used to change the attributes of a user

For instance, to add a user to an existing group we use usermod

sudo usermod -aG <groupname> <username>

Exmple: Lets add a user tester4 to the group qa

sudo usermod -aG qa tester4