What does the usermod command do?

The usermod command in Linux is used to modify user accounts. It allows you to change various attributes of a user account without deleting and recreating it. Some common uses of the usermod command include:

• Adding a user to supplementary groups with the -aG option.
• Changing a user's login shell with the -s option.
• Setting up a home directory for a user with the -d -m option.
• Renaming a user with the -l option.
• Setting account expiration dates with the -e option.

Here’s an example of adding a user to a group:

sudo usermod -aG groupname username

This command appends the specified user to the given group.