How to add a user to a secondary group?

To add a user to a secondary group in Linux, you can use the usermod command with the -aG option. Here’s how to do it:

Open the Terminal.
Use the usermod Command:
The syntax for adding a user to a secondary group is as follows:
```
sudo usermod -aG groupname username
```
- Replace groupname with the name of the secondary group you want to add the user to.
- Replace username with the name of the user you want to add.
Example:
If you want to add a user named joker to a secondary group called developers, you would run:
```
sudo usermod -aG developers joker
```
Verify the Change:
After adding the user to the secondary group, you can verify the change by using the groups command:
```
groups joker
```
This will show all the groups that the user joker belongs to, including the newly added secondary group.

Note: The -a option is important because it appends the user to the specified group without removing them from any other groups they are already a member of.