group

Add an existing user to secondary/supplementary user group using the -a option

usermod -a -G groupname useraccount;

The usermod command is a Linux utility used to modify the user account information stored in the /etc/passwd and /etc/group files. The -a option is used to append the specified user account to the specified group. The -G option is used to specify the group name that the user account will be added to. The groupname argument is the name of the group that the user account will be added to, and the useraccount argument is the name of the user account that will be added to the group.

In this command, the user account specified by “useraccount” will be added to the group specified by “groupname”. The -a option ensures that the user account will be added to the specified group without removing it from any other groups it may belong to. The -G option specifies that the user account will be added to the specified group as a secondary group.

Once the user account has been added to the specified group, it will have the permissions and access rights associated with that group. For example, if the group has permissions to read and write to certain files or directories, then the user account will also have these permissions once it has been added to the group.

It’s important to note that changes made with the “usermod” command are not applied immediately. The changes will take effect after the next time the user logs in or after a system reboot. Additionally, it’s important to use this command with caution as adding a user to the wrong group could grant unintended access rights to sensitive information.

In conclusion, the usermod -a -G groupname useraccount command is a useful tool for managing user accounts and group memberships in Linux systems. By adding a user account to a specific group, administrators can grant the user access to specific resources and permissions, making it easier to manage and control access to resources on a system.