It is generally not recommended to create usernames or groups in all uppercase letters in a Unix or Linux system, as some systems and applications may not handle uppercase letters correctly. In general, it is best to stick to lowercase letters and numbers when creating usernames and groups to avoid potential issues.
However, if you need to create a username or group in all uppercase letters, you can use the useradd and groupadd commands with the -U option to create a new user or group in all uppercase letters.
For example, to create a new user with the username USER1 in all uppercase letters, you can use the following command:
sudo useradd -U USER1
To create a new group with the group name GROUP1 in all uppercase letters, you can use the following command:
sudo groupadd -U GROUP1
Keep in mind that some systems and applications may not handle uppercase letters correctly, and you may encounter issues when using usernames or groups with all uppercase letters. It is generally recommended to use lowercase letters and numbers when creating usernames and groups to avoid potential issues.