nixpkgs/nixos/doc/manual/configuration/user-mgmt.xml

<chapter xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         version="5.0"
         xml:id="sec-user-management">

<title>User Management</title>

<para>NixOS supports both declarative and imperative styles of user
management.  In the declarative style, users are specified in
<filename>configuration.nix</filename>.  For instance, the following
states that a user account named <literal>alice</literal> shall exist:

<programlisting>
users.extraUsers.alice =
  { isNormalUser = true;
    home = "/home/alice";
    description = "Alice Foobar";
    extraGroups = [ "wheel" "networkmanager" ];
    openssh.authorizedKeys.keys = [ "ssh-dss AAAAB3Nza... alice@foobar" ];
  };
</programlisting>

Note that <literal>alice</literal> is a member of the
<literal>wheel</literal> and <literal>networkmanager</literal> groups,
which allows her to use <command>sudo</command> to execute commands as
<literal>root</literal> and to configure the network, respectively.
Also note the SSH public key that allows remote logins with the
corresponding private key. Users created in this way do not have a
password by default, so they cannot log in via mechanisms that require
a password. However, you can use the <command>passwd</command> program
to set a password, which is retained across invocations of
<command>nixos-rebuild</command>.</para>

<para>If you set users.mutableUsers to false, then the contents of /etc/passwd
and /etc/group will be congruent to your NixOS configuration. For instance,
if you remove a user from users.extraUsers and run nixos-rebuild, the user
account will cease to exist. Also, imperative commands for managing users
and groups, such as useradd, are no longer available.</para>

<para>A user ID (uid) is assigned automatically.  You can also specify
a uid manually by adding

<programlisting>
    uid = 1000;
</programlisting>

to the user specification.</para>

<para>Groups can be specified similarly.  The following states that a
group named <literal>students</literal> shall exist:

<programlisting>
users.extraGroups.students.gid = 1000;
</programlisting>

As with users, the group ID (gid) is optional and will be assigned
automatically if it’s missing.</para>

<para>In the imperative style, users and groups are managed by
commands such as <command>useradd</command>,
<command>groupmod</command> and so on.  For instance, to create a user
account named <literal>alice</literal>:

<screen>
# useradd -m alice</screen>

To make all nix tools available to this new user use `su - USER` which 
opens a login shell (==shell that loads the profile) for given user. 
This will create the ~/.nix-defexpr symlink. So run:

<screen>
# su - alice -c "true"</screen>


The flag <option>-m</option> causes the creation of a home directory
for the new user, which is generally what you want.  The user does not
have an initial password and therefore cannot log in.  A password can
be set using the <command>passwd</command> utility:

<screen>
# passwd alice
Enter new UNIX password: ***
Retype new UNIX password: ***
</screen>

A user can be deleted using <command>userdel</command>:

<screen>
# userdel -r alice</screen>

The flag <option>-r</option> deletes the user’s home directory.
Accounts can be modified using <command>usermod</command>.  Unix
groups can be managed using <command>groupadd</command>,
<command>groupmod</command> and <command>groupdel</command>.</para>

</chapter>