lix/doc/manual/nix-copy-closure.xml

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          xmlns:xlink="http://www.w3.org/1999/xlink"
          xmlns:xi="http://www.w3.org/2001/XInclude"
          xml:id="sec-nix-copy-closure">

<refmeta>
  <refentrytitle>nix-copy-closure</refentrytitle>
  <manvolnum>1</manvolnum>
  <refmiscinfo class="source">Nix</refmiscinfo>
  <refmiscinfo class="version"><xi:include href="version.txt" parse="text"/></refmiscinfo>
</refmeta>

<refnamediv>
  <refname>nix-copy-closure</refname>
  <refpurpose>copy a closure to or from a remote machine via SSH</refpurpose>
</refnamediv>

<refsynopsisdiv>
  <cmdsynopsis>
    <command>nix-copy-closure</command>
    <group>
      <arg choice='plain'><option>--to</option></arg>
      <arg choice='plain'><option>--from</option></arg>
    </group>
    <arg><option>--sign</option></arg>
    <arg><option>--gzip</option></arg>
    <arg choice='plain'>
      <arg><replaceable>user@</replaceable></arg><replaceable>machine</replaceable>
    </arg>
    <arg choice='plain'><replaceable>paths</replaceable></arg>
  </cmdsynopsis>
</refsynopsisdiv>


<refsection><title>Description</title>

<para><command>nix-copy-closure</command> gives you an easy and
efficient way to exchange software between machines.  Given one or
more Nix store paths <replaceable>paths</replaceable> on the local
machine, <command>nix-copy-closure</command> computes the closure of
those paths (i.e. all their dependencies in the Nix store), and copies
all paths in the closure to the remote machine via the
<command>ssh</command> (Secure Shell) command.  With the
<option>--from</option>, the direction is reversed:
the closure of <replaceable>paths</replaceable> on a remote machine is
copied to the Nix store on the local machine.</para>

<para>This command is efficient because it only sends the store paths
that are missing on the target machine.</para>

<para>Since <command>nix-copy-closure</command> calls
<command>ssh</command>, you may be asked to type in the appropriate
password or passphrase.  In fact, you may be asked
<emphasis>twice</emphasis> because <command>nix-copy-closure</command>
currently connects twice to the remote machine, first to get the set
of paths missing on the target machine, and second to send the dump of
those paths.  If this bothers you, use
<command>ssh-agent</command>.</para>


<refsection><title>Options</title>

<variablelist>
  
  <varlistentry><term><option>--to</option></term>

    <listitem><para>Copy the closure of
    <replaceable>paths</replaceable> from the local Nix store to the
    Nix store on <replaceable>machine</replaceable>.  This is the
    default.</para></listitem>

  </varlistentry>

  <varlistentry><term><option>--from</option></term>

    <listitem><para>Copy the closure of
    <replaceable>paths</replaceable> from the Nix store on
    <replaceable>machine</replaceable> to the local Nix
    store.</para></listitem>

  </varlistentry>

  <varlistentry><term><option>--sign</option></term>

    <listitem><para>Let the sending machine cryptographically sign the
    dump of each path with the key in
    <filename>/nix/etc/nix/signing-key.sec</filename>.  If the user on
    the target machine does not have direct access to the Nix store
    (i.e., if the target machine has a multi-user Nix installation),
    then the target machine will check the dump against
    <filename>/nix/etc/nix/signing-key.pub</filename> before unpacking
    it in its Nix store.  This allows secure sharing of store paths
    between untrusted users on two machines, provided that there is a
    trust relation between the Nix installations on both machines
    (namely, they have matching public/secret keys).</para></listitem>

  </varlistentry>

  <varlistentry><term><option>--gzip</option></term>

    <listitem><para>Compress the dump of each path with
    <command>gzip</command> before sending it.</para></listitem>

  </varlistentry>

</variablelist>

</refsection>


<refsection><title>Environment variables</title>

<variablelist>

  <varlistentry><term><envar>NIX_SSHOPTS</envar></term>

    <listitem><para>Additional options to be passed to
    <command>ssh</command> on the command line.</para></listitem>

  </varlistentry>
  
</variablelist>

</refsection>


<refsection><title>Examples</title>

<para>Copy Firefox with all its dependencies to a remote machine:

<screen>
$ nix-copy-closure --to alice@itchy.labs $(type -tP firefox)</screen>

</para>

<para>Copy Subversion from a remote machine and then install it into a
user environment:

<screen>
$ nix-copy-closure --from alice@itchy.labs \
    /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
$ nix-env -i /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
</screen>

</para>

</refsection>


</refsection>

</refentry>