How to Add a User in Ubuntu

How do I add a user in Ubuntu?

Without a home directory

sudo useradd myuser

With home directory

sudo useradd -m myuser

Then set the password

sudo passwd myuser

Then set the shell

sudo usermod -s /bin/bash myuser

How do I add a user to multiple groups in Ubuntu?

The utility is usermod and is used like:

usermod -a -G group1,group2 username

Where username is the user you want to modify and group1 and group2 are the new groups you want that user to join. Running the command without the -a argument will remove that user from all groups except group1 and group2.

To check a users group memberships use the groups command:

groups username

I can't add a new user in Ubuntu Linux

visudo doesn't add users. Try useradd, adduser, or (if you know what you are doing) vipw.

However, if all you are trying to do is log in, just reset Sr. X's password as root:

# passwd userX
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Ubuntu adding a user not setting a home directory

It is right there in the man page for useradd(8):

   -m, --create-home
       Create the user's home directory if it does not exist. The files and directories contained
       in the skeleton directory (which can be defined with the -k option) will be copied to the
       home directory.

       By default, if this option is not specified and CREATE_HOME is not enabled, no home
       directories are created.

Add a Ubuntu User from Web Interface

Probably the best option is to create a setuid program that adds the user and then use exec or similar to call it.

Ubuntu 18.04 - Add new user and initialize it

You can try using xdg-user-dirs-update tool which generates all required user directories in the $HOME path.

Don't forget to do su newuser first.

How to add users to Docker container?

The trick is to use useradd instead of its interactive wrapper adduser.
I usually create users with:

RUN useradd -ms /bin/bash newuser

which creates a home directory for the user and ensures that bash is the default shell.

You can then add:

USER newuser
WORKDIR /home/newuser

to your dockerfile. Every command afterwards as well as interactive sessions will be executed as user newuser:

docker run -t -i image
newuser@131b7ad86360:~$

You might have to give newuser the permissions to execute the programs you intend to run before invoking the user command.

Using non-privileged users inside containers is a good idea for security reasons. It also has a few drawbacks. Most importantly, people deriving images from your image will have to switch back to root before they can execute commands with superuser privileges.

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