<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>
<xref linkend="opt-users.users"/>.alice = {
  <link linkend="opt-users.users._name__.isNormalUser">isNormalUser</link> = true;
  <link linkend="opt-users.users._name__.home">home</link> = "/home/alice";
  <link linkend="opt-users.users._name__.description">description</link> = "Alice Foobar";
  <link linkend="opt-users.users._name__.extraGroups">extraGroups</link> = [ "wheel" "networkmanager" ];
  <link linkend="opt-users.users._name__.openssh.authorizedKeys.keys">openssh.authorizedKeys.keys</link> = [ "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 <xref linkend="opt-users.mutableUsers"/> to false, then the
  contents of <literal>/etc/passwd</literal> and <literal>/etc/group</literal>
  will be congruent to your NixOS configuration. For instance, if you remove a
  user from <xref linkend="opt-users.users"/> 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. Passwords may still be
  assigned by setting the user's
  <link linkend="opt-users.users._name__.hashedPassword">hashedPassword</link>
  option. A hashed password can be generated using <command>mkpasswd -m
  sha-512</command> after installing the <literal>mkpasswd</literal> package.
 </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>
<xref linkend="opt-users.groups"/>.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>
