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diff --git a/doc/manual/package-management.xml b/doc/manual/package-management.xml index be0d5f21bf1c..c22273ebe31d 100644 --- a/doc/manual/package-management.xml +++ b/doc/manual/package-management.xml @@ -528,4 +528,82 @@ linkend='sec-nix-install-package' /> for details.</para> </section> +<section xml:id="sec-sharing-packages"><title>Sharing packages between machines</title> + +<para>Sometimes you want to copy a package from one machine to +another. Or, you want to install some packages and you know that +another machine already has some or all of those packages or their +dependencies. In that case there are mechanisms to quickly copy +packages between machines.</para> + +<para>The command <command +linkend="sec-nix-copy-closure">nix-copy-closure</command> copies a Nix +store path along with all its dependencies to or from another machine +via the SSH protocol. It doesn’t copy store paths that are already +present on the target machine. For example, the following command +copies Firefox with all its dependencies: + +<screen> +$ nix-copy-closure --to alice@itchy.example.org $(type -p firefox)</screen> + +See <xref linkend='sec-nix-copy-closure' /> for details.</para> + +<para>With <command linkend='refsec-nix-store-export'>nix-store +--export</command> and <command +linkend='refsec-nix-store-import'>nix-store --import</command> you can +write the closure of a store path (that is, the path and all its +dependencies) to a file, and then unpack that file into another Nix +store. For example, + +<screen> +$ nix-store --export $(type -p firefox) > firefox.closure</screen> + +writes the closure of Firefox to a file. You can then copy this file +to another machine and install the closure: + +<screen> +$ nix-store --import < firefox.closure</screen> + +Any store paths in the closure that are already present in the target +store are ignored. It is also possible to pipe the export into +another command, e.g. to copy and install a closure directly to/on +another machine: + +<screen> +$ nix-store --export $(type -p firefox) | bzip2 | \ + ssh alice@itchy.example.org "bunzip2 | nix-store --import"</screen> + +But note that <command>nix-copy-closure</command> is generally more +efficient in this example because it only copies paths that are not +already present in the target Nix store.</para> + +<para>Finally, if you can mount the Nix store of a remote machine in +your local filesystem, Nix can copy paths from the remote Nix store to +the local Nix store <emphasis>on demand</emphasis>. For instance, +suppose that you mount a remote machine containing a Nix store via +<command +xlink:href="http://fuse.sourceforge.net/sshfs.html">sshfs</command>: + +<screen> +$ sshfs alice@itchy.example.org:/ /mnt</screen> + +You should then set the <envar>NIX_OTHER_STORES</envar> environment +variable to tell Nix about this remote Nix store: + +<screen> +$ export NIX_OTHER_STORES=/mnt/nix</screen> + +Then if you do any Nix operation, e.g. + +<screen> +$ nix-env -i firefox</screen> + +and Nix has to build a path that it sees is already present in +<filename>/mnt/nix</filename>, then it will just copy from there +instead of building it from source.</para> + + +</section> + + </chapter> |