talks: Add slides for GPCE 2017.

.gitignore

@@ -127,3 +127,11 @@
 /doc/gpce-2017/gpce.out
 /doc/gpce-2017/gpce.pdf
 /doc/gpce-2017/gpce.tex
+/talks/gpce-2017/talk.aux
+/talks/gpce-2017/talk.log
+/talks/gpce-2017/talk.nav
+/talks/gpce-2017/talk.out
+/talks/gpce-2017/talk.pdf
+/talks/gpce-2017/talk.snm
+/talks/gpce-2017/talk.toc
+/talks/gpce-2017/talk.vrb

talks/gpce-2017/images/GuixSD-horizontal-print.pdf

@@ -0,0 +1 @@
+../../ghm-2016/update/images/GuixSD-horizontal-print.pdf

talks/gpce-2017/images/GuixSD.pdf

@@ -0,0 +1 @@
+../../ghm-2016/update/images/GuixSD.pdf

talks/gpce-2017/rules.ini

@@ -0,0 +1,9 @@
+;; Rules for Rubber.
+
+[dot-pdf]
+target = (.*)\.pdf
+source = \1.dot
+rule = shell
+cost = 0
+command = dot -Tpdf -Gratio=.78 -o $target $source
+message = rendering $source into $target

talks/gpce-2017/talk.tex

@@ -0,0 +1,646 @@
+% The comment below tells Rubber to compile the .dot files.
+%
+% rubber: module graphics
+% rubber: rules rules.ini
+
+\documentclass[aspectratio=169]{beamer}
+
+\usetheme{default}
+
+\usefonttheme{structurebold}
+\usepackage{helvet}
+\usecolortheme{seagull}         % white on black
+
+\usepackage[utf8]{inputenc}
+\PassOptionsToPackage{hyphens}{url}\usepackage{hyperref,xspace,multicol}
+\usepackage[absolute,overlay]{textpos}
+\usepackage{tikz}
+\usetikzlibrary{arrows,shapes,trees,shadows,positioning}
+\usepackage{fancyvrb}           % for \Verb
+
+% For '⇝'.
+\DeclareUnicodeCharacter{21DD}{$\rightsquigarrow$}
+
+% Remember the position of every picture.
+\tikzstyle{every picture}+=[remember picture]
+
+\tikzset{onslide/.code args={<#1>#2}{%
+  \only<#1>{\pgfkeysalso{#2}} % \pgfkeysalso doesn't change the path
+}}
+
+% Colors.
+\definecolor{guixred1}{RGB}{226,0,38}  % red P
+\definecolor{guixorange1}{RGB}{243,154,38}  % guixorange P
+\definecolor{guixyellow}{RGB}{254,205,27}  % guixyellow P
+\definecolor{guixred2}{RGB}{230,68,57}  % red S
+\definecolor{guixred3}{RGB}{115,34,27}  % dark red
+\definecolor{guixorange2}{RGB}{236,117,40}  % guixorange S
+\definecolor{guixtaupe}{RGB}{134,113,127} % guixtaupe S
+\definecolor{guixgrey}{RGB}{91,94,111} % guixgrey S
+\definecolor{guixdarkgrey}{RGB}{46,47,55} % guixdarkgrey S
+\definecolor{guixblue1}{RGB}{38,109,131} % guixblue S
+\definecolor{guixblue2}{RGB}{10,50,80} % guixblue S
+\definecolor{guixgreen1}{RGB}{133,146,66} % guixgreen S
+\definecolor{guixgreen2}{RGB}{157,193,7} % guixgreen S
+
+\setbeamerfont{title}{size=\huge}
+\setbeamerfont{frametitle}{size=\huge}
+\setbeamerfont{normal text}{size=\Large}
+
+% White-on-black color theme.
+\setbeamercolor{structure}{fg=guixorange1,bg=black}
+\setbeamercolor{title}{fg=white,bg=black}
+\setbeamercolor{date}{fg=guixorange1,bg=black}
+\setbeamercolor{frametitle}{fg=white,bg=black}
+\setbeamercolor{titlelike}{fg=white,bg=black}
+\setbeamercolor{normal text}{fg=white,bg=black}
+\setbeamercolor{alerted text}{fg=guixyellow,bg=black}
+\setbeamercolor{section in toc}{fg=white,bg=black}
+\setbeamercolor{section in toc shaded}{fg=white,bg=black}
+\setbeamercolor{subsection in toc}{fg=guixorange1,bg=black}
+\setbeamercolor{subsection in toc shaded}{fg=white,bg=black}
+\setbeamercolor{subsubsection in toc}{fg=guixorange1,bg=black}
+\setbeamercolor{subsubsection in toc shaded}{fg=white,bg=black}
+\setbeamercolor{frametitle in toc}{fg=white,bg=black}
+\setbeamercolor{local structure}{fg=guixorange1,bg=black}
+
+\newcommand{\highlight}[1]{\alert{\textbf{#1}}}
+
+\title{Code Staging in GNU Guix}
+
+\author{Ludovic Courtès}
+\date{\small{GPCE\\23 October 2017, Vancouver, Canada}}
+
+\setbeamertemplate{navigation symbols}{} % remove the navigation bar
+
+\AtBeginSection[]{
+  \begin{frame}
+    \frametitle{}
+    \tableofcontents[currentsection]
+  \end{frame} 
+}
+
+
+\newcommand{\screenshot}[1]{
+  \begin{frame}[plain]
+    \begin{tikzpicture}[remember picture, overlay]
+      \node [at=(current page.center), inner sep=0pt]
+        {\includegraphics[width=\paperwidth]{#1}};
+    \end{tikzpicture}
+  \end{frame}
+}
+
+
+%% \usepackage{pgfpages}
+%% \setbeameroption{second mode text on second screen}
+%% \setbeameroption{previous slide on second screen}
+
+\begin{document}
+
+\begin{frame}[plain, fragile]
+  \vspace{10mm}
+  \titlepage
+
+  \vfill{}
+  \hfill{\includegraphics[width=0.2\paperwidth]{images/inria-logo-inverse-en-2017}}
+\end{frame}
+
+%% \begin{frame}[typeset second]
+%%   This text is shown on the left and on the right.
+%%   \only<second>{This text is only shown on the right.}
+%%   \only<second:0>{This text is only shown on the left.}
+%% \end{frame}
+
+\setbeamercolor{normal text}{bg=guixblue2}
+\begin{frame}
+  \Huge{\textbf{Functional software deployment.}}
+\end{frame}
+\setbeamercolor{normal text}{fg=white,bg=black}
+
+\setbeamercolor{normal text}{fg=white,bg=black}
+\begin{frame}[fragile]
+
+  \begin{semiverbatim}
+    \Large{
+\$ guix package -i emacs ocaml idris ghc
+\textrm{...}
+
+\$ guix package -r emacs -i vim
+\textrm{...}
+\pause
+\$ guix package --roll-back
+\textrm{...}
+}
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]
+  \begin{semiverbatim}
+    \small{
+(\alert{operating-system}
+  (host-name "gastown")
+  (timezone "Canada/Pacific")
+  (locale "fr_CA.utf8")
+  (bootloader (grub-configuration (device "/dev/sda")))
+  (file-systems (cons (\alert{file-system}
+                        (device "my-root")
+                        (title 'label)
+                        (mount-point "/")
+                        (type "ext4"))
+                      %base-file-systems))
+  (users (cons (\alert{user-account}
+                 (name "alice")
+                 (group "users")
+                 (home-directory "/home/alice"))
+               %base-user-accounts))
+  (services (cons (\alert{service} openssh-service-type)
+                  %base-services)))
+    }
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]
+
+  \begin{semiverbatim}
+    \Large{
+\$ guix system vm config.scm
+\textrm{...}
+
+\$ guix system reconfigure config.scm
+\textrm{...}
+
+\$ guix system roll-back
+\textrm{...}
+}
+  \end{semiverbatim}
+\end{frame}
+
+\setbeamercolor{normal text}{bg=guixdarkgrey,fg=guixred3}
+\begin{frame}[fragile]
+  \vspace{2cm}
+  \Large{
+    \textbf{Functional} software deployment paradigm:
+
+    \begin{enumerate}
+    \item build process = \highlight{pure function}
+    \item built software = \highlight{persistent graph}
+    \end{enumerate}
+  }
+
+  \vfill{}
+  \small{
+    \textit{Imposing a Memory Management Discipline on
+      Software Deployment}, Dolstra et al., 2004 (Nix package manager)
+  }
+\end{frame}
+\setbeamercolor{normal text}{fg=white,bg=black}
+
+\begin{frame}[fragile]
+  \begin{semiverbatim}
+    \small{
+(define hello
+  (\alert{package}
+    (name "hello")
+    (version "2.10")
+    (source (\alert{origin}
+              (method url-fetch)
+              (uri (string-append "https://ftp.gnu.org/\textrm{...}/hello-"
+                                  version ".tar.gz"))
+              (sha256 (base32 "0wqd\textrm{...}dz6"))))
+    (build-system gnu-build-system)
+    (synopsis "An example GNU package")
+    (description "Produce a friendly greeting.")
+    (home-page "https://gnu.org/software/hello/")
+    (license gpl3+)))
+}
+  \end{semiverbatim}
+
+  \vfill{}
+  \small{
+    \textit{Functional Package Management with Guix}, Courtès, 2013
+  }
+\end{frame}
+
+\begin{frame}[fragile]
+
+  \begin{semiverbatim}
+    \Large{
+\$ guix build hello
+\uncover<2->{/gnu/store/\tikz[baseline]{\node[anchor=base](nixhash){\alert<2>{sp4wxa09zxfcs4vchm6as014msa5yi22}};}-hello-2.10}
+}
+  \end{semiverbatim}
+
+  \begin{textblock}{7}(4, 10)
+    \only<2>{\tikz{\node(labelnixhash)[fill=white, text=black,
+          rounded corners=2mm, inner sep=4mm]
+        {\textbf{\Large{hash of \emph{all} the dependencies}};}}}
+  \end{textblock}
+
+  % Arrows
+  \only<2>{
+    \begin{tikzpicture}[overlay]
+      \path[->](labelnixhash.north) edge [bend left, in=180, out=-45] (nixhash.south);
+    \end{tikzpicture}
+  }
+\end{frame}
+
+\setbeamercolor{normal text}{fg=black,bg=white}
+\begin{frame}[fragile]{}
+  \begin{tikzpicture}[tools/.style = {
+                        text width=65mm, minimum height=3cm,
+                        text badly ragged,
+                        rounded corners=2mm,
+                        fill=black, text=white
+                      },
+                      tool/.style = {
+                        fill=black, text=white, text width=6cm,
+                        text centered
+                      },
+                      daemon/.style = {
+                        rectangle, text width=50mm, text centered,
+                        rounded corners=2mm, minimum height=15mm,
+                        top color=guixorange1,
+                        bottom color=guixyellow,
+                        text=black
+                      },
+                      builders/.style = {
+                        draw=guixorange1, very thick, dashed,
+                        fill=white, text=black, text width=5cm,
+                        rounded corners=2mm,
+                      },
+                      builder/.style = {
+                        draw=guixred2, thick, rectangle,
+                        fill=guixgrey, rotate=90
+                      }]
+    \matrix[row sep=7mm, column sep=18mm] {
+      \node(builders)[builders, text height=5cm]{}
+          node[fill=white, text=black] at (0, 2) {\large{\textbf{build processes}}}
+          node[fill=white, text=black] at (0, 1.5) {chroot, separate UIDs}
+          node[builder, onslide=<1-2>{white}] at (-1,-0.5) {\alert<3->{Guile}, make, etc.}
+          node[builder, onslide=<1-2>{white}] at ( 0,-0.5) {\alert<3->{Guile}, make, etc.}
+          node[builder, onslide=<1-2>{white}] at ( 1,-0.5) {\alert<3->{Guile}, make, etc.}; &
+      \node[tools]{}
+          node[fill=black, text=white] at (0, 1) {\large{\textbf{Guile Scheme}}}
+          node(client)[tool] at (0, 0)
+          {\texttt{(define hello (\alert{package} \textrm{...}))}};
+      \\
+
+      \node(daemon)[daemon]{\large{\textbf{build daemon}}}; &
+      &
+      \\
+    };
+  \end{tikzpicture}
+
+  \begin{tikzpicture}[overlay]
+    \path[very thick, draw=guixorange1]<2->
+      (client.south) edge [out=-90, in=0, ->, text=black] node[below, sloped]{RPCs} (daemon.east);
+    \path[->, very thick, draw=guixorange1]<3->
+      (daemon) edge (builders);
+  \end{tikzpicture}
+\end{frame}
+\setbeamercolor{normal text}{fg=white,bg=black}
+
+% TODO: Scheme all the way down + image.
+
+\setbeamercolor{normal text}{bg=guixblue2}
+\begin{frame}
+  \Huge{\textbf{Code staging.}}
+\end{frame}
+\setbeamercolor{normal text}{fg=white,bg=black}
+
+\begin{frame}[fragile]{Staging: take \#1}
+  \vspace{-0.2cm}
+  \begin{semiverbatim}
+(define \alert{build-exp}
+  ;; \textsl{Build-side code.}
+  '(symlink \only<1>{\textsl{"/gnu/store/123\textrm{...}-coreutils-8.25"}}\only<2->{(assoc-ref \alert{%build-inputs} "coreutils")}
+            \only<1>{\textsl{"/gnu/store/abc\textrm{...}-result"}}\only<2->{\alert{%output}}))
+\uncover<2->{
+;; \textsl{... with unhygienic global variable:}
+;; (define %build-inputs
+;;   '(\only<2>{("coreutils" . "/gnu/store/\textrm{...}-coreutils-8.25")}\only<3>{}))
+
+\uncover<2>{(define \alert{inputs}
+  ;; \textsl{What goes into the chroot.}
+  `(("coreutils" ,coreutils)))}
+
+(build-expression->derivation store "symlink-to-coreutils"
+                              \alert{build-exp}
+                              \uncover<2>{#:inputs \alert{inputs}})}
+\pause
+  \end{semiverbatim}
+\end{frame}
+
+\setbeamercolor{normal text}{bg=guixdarkgrey}
+\begin{frame}
+  \Large{
+    \begin{itemize}
+    \item Nix: generates Bash code through string interpolation
+    \item \textit{Writing Hygienic Macros in Scheme with Syntax-Case},
+      (Dybvig, 1992)
+    \item \textit{A Multi-Tier Semantics for Hop} (Serrano \& Queinnec,
+      2010)
+    \end{itemize}
+  }
+\end{frame}
+\setbeamercolor{normal text}{fg=white,bg=black}
+
+\begin{frame}[fragile]{Take \#2: G-expressions}
+  \begin{semiverbatim}
+(define \alert{build-exp}
+  ;; \textsl{First-class object that carries info}
+  ;; \textsl{about its dependencies.}
+  (\alert{gexp} (symlink (\alert{ungexp} coreutils)
+                 (\alert{ungexp output}))))
+
+;; \textsl{Leads to a build script like:}
+;; (symlink "/gnu/store/123\textrm{...}-coreutils-8.25"
+;;          (getenv "out"))
+
+(gexp->derivation "symlink-to-coreutils" \alert{build-exp})
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Take \#2: G-expressions}
+  \begin{semiverbatim}
+(define \alert{build-exp}
+  ;; \textsl{First-class object that carries info}
+  ;; \textsl{about its dependencies.}
+  \alert{#~}(symlink \alert{#$}coreutils \alert{#$output}))
+
+;; \textsl{Leads to a build script like:}
+;; (symlink "/gnu/store/\only<1>{123}\only<2>{h8a}\textrm{...}-coreutils-8.25"
+;;          (getenv "out"))
+
+(gexp->derivation "symlink-to-coreutils" \alert{build-exp}\only<1>{)}
+                  \only<2>{\alert{#:system} "i686-linux")}
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Modules}
+  \begin{semiverbatim}
+(define \alert{build-exp}
+\uncover<2>{  ;; \textsl{Compile (guix build utils) and add it}
+  ;; \textsl{to the chroot.}
+  (\alert{with-imported-modules} '((guix build utils))}
+    \alert{#~}(begin
+        (\alert{use-modules} (guix build utils))
+        (mkdir-p (string-append \alert{#$output} "/bin"))\only<2>{)}
+
+(gexp->derivation "empty-bin-dir" build-exp)
+\only<1>{;; \textsl{ERROR: (guix build utils) not found!}}
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Initial RAM Disk}
+  \begin{semiverbatim}
+(expression->initrd
+ (\alert{with-imported-modules} (source-module-closure
+                         '((gnu build linux-boot)
+                           (guix build utils)))
+   \alert{#~}(begin
+       (\alert{use-modules} (gnu build linux-boot)
+                    (guix build utils))
+
+       (boot-system #:mounts '#$file-systems
+                    #:linux-modules '#$linux-modules
+                    #:linux-module-directory '#$kodir)))
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Towards More Use Cases...}
+  \begin{semiverbatim}
+(\alert{eval-remotely} \alert{#~}(system* \alert{#$}(file-append ffmpeg "/bin/ffmpeg") \textrm{...})
+               (open-ssh-session "example.org"))
+
+(\alert{eval-in-vm} \alert{#~}(uname) vm)
+
+\textrm{...}
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Scope Preservation}
+  \vspace{-5mm}
+  \begin{semiverbatim}
+    \Large{
+(let ((gen-body (lambda (x)
+                  \alert{#~}(let ((x 40))
+                      (+ x \alert{#$}x)))))
+  \alert{#~}(let ((x 2))
+      \alert{#$}(gen-body \alert{#~}x))
+\pause
+⇝ (let ((\alert{x-1bd8-0} 2))
+    (let ((x-4f05-0 40))
+      (+ x-4f05-0 \alert{x-1bd8-0})))
+}
+  \end{semiverbatim}
+  \vspace{-10mm}
+  \small{
+    Dybvig 1992, Kiselyov 2008, Rhiger 2012
+  }
+\end{frame}
+
+\setbeamercolor{normal text}{bg=guixred3}
+\setbeamercolor{frametitle}{bg=guixred3}
+\begin{frame}[fragile]{Limitations}
+  \Large{
+    \begin{itemize}
+    \item hygiene vs. \highlight{macro-introduced bindings}?
+    \item \highlight{modules} in scope?
+    \item \highlight{serialization} of non-primitive data types?
+    \item cross-stage \highlight{debugging info} à la Hop?
+    \end{itemize}
+  }
+\end{frame}
+\setbeamercolor{frametitle}{bg=black}
+\setbeamercolor{normal text}{bg=black}
+
+\setbeamercolor{normal text}{bg=guixblue2}
+\begin{frame}
+  \Huge{\textbf{Summary.}}
+\end{frame}
+\setbeamercolor{normal text}{fg=white,bg=black}
+
+\setbeamercolor{normal text}{bg=guixgrey}
+\begin{frame}[fragile]
+  \LARGE{
+    \begin{itemize}
+    \item G-exps \highlight{tie staging to software deployment}
+    \item \highlight{used at scale in Guix}
+    \item entirely \highlight{implemented as a macro}
+    \end{itemize}
+  }
+\end{frame}
+\setbeamercolor{normal text}{fg=white,bg=black}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[plain]
+
+\vfill{
+  \vspace{2.5cm}
+  \center{\includegraphics[width=0.5\textwidth]{images/GuixSD-horizontal}}\\[1.0cm]
+  \texttt{ludo@gnu.org}\hfill{\alert{\url{https://gnu.org/software/guix/}}}
+}
+
+\end{frame}
+
+\setbeamercolor{normal text}{bg=guixred3}
+\begin{frame}
+  \Huge{\textbf{Ghost track!}}
+\end{frame}
+\setbeamercolor{normal text}{fg=white,bg=black}
+
+\begin{frame}[fragile]{Cross-Compilation}
+  \begin{semiverbatim}
+(gexp->derivation "vi"
+   \alert{#~}(begin
+       (mkdir \alert{#$output})
+       (system* (string-append \alert{#+}coreutils "/bin/ln")
+                "-s"
+                (string-append \alert{#$}emacs "/bin/emacs")
+                (string-append \alert{#$}output "/bin/vi")))
+\only<2>{   \alert{#:target} "mips64el-linux-gnu"})
+
+;; \textsl{Yields:}
+;; (begin
+;;   (mkdir (getenv "out"))
+;;   (system* (string-append "/gnu/store/123\textrm{...}" "/bin/ln")
+;;            "-s"
+;;            (string-append "/gnu/store/\only<1>{345}\only<2>{\alert{9ab}}\textrm{...}" \textrm{...})
+;;            (string-append "/gnu/store/\only<1>{567}\only<2>{\alert{fc2}}\textrm{...}" \textrm{...})))
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Defining ``Compilers''}
+  \begin{semiverbatim}
+    \small{
+(\alert{define-gexp-compiler} (package-compiler (package \alert{<package>})
+                                        system target)
+  ;; \textsl{Return a derivation to build PACKAGE.}
+  (if target
+      (package->cross-derivation package target system)
+      (package->derivation package system)))
+    }
+\pause
+(define-record-type \alert{<plain-file>}
+  (plain-file name content)
+  \textrm{...})
+
+(\alert{define-gexp-compiler} (plain-file-compiler (file \alert{<plain-file>})
+                                           system target)
+  ;; \textsl{"Compile" FILE by adding it to the store.}
+  (match file
+    (($ \alert{<plain-file>} name content)
+     (text-file name content))))
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Compilers \& ``Expanders''}
+  \begin{semiverbatim}
+\alert{#~}(string-append \alert{#$}coreutils "/bin/ls")
+
+;; \textsl{Yields:}
+;; (string-append "/gnu/store/\textrm{...}" "/bin/ls")
+\pause
+(file-append coreutils "/bin/ls")
+
+;; \textsl{Yields:}
+;; "/gnu/store/\textrm{...}/bin/ls"
+  \end{semiverbatim}
+\end{frame}
+
+\begin{frame}[fragile]
+  \begin{overlayarea}{\textwidth}{8cm}
+  \begin{tikzpicture}[kernel/.style = {
+                        text width=10cm, minimum height=1.4cm,
+                        text centered,
+                        rounded corners=2mm,
+                        fill=white, text=black
+                      },
+                      userland/.style = {
+                        draw=guixorange1, very thick,
+                        fill=white, text=black, text width=6cm,
+                        rounded corners=2mm, minimum height=1.4cm,
+                        text centered
+                      }]
+    \matrix[row sep=6mm, column sep=1cm] {
+      \node(kernel)[kernel]{\textbf{\Large{Linux-libre}}};
+      \\
+
+      \node<2->(initrd)[userland]{\textbf{\Large{initial RAM disk}}};
+      \\
+
+      \node<4->(shepherd)[userland]{\textbf{\Large{PID 1: GNU Shepherd}}
+        \\ services...};
+      \\
+
+      \node<6->(user)[userland, dashed]{\textbf{\Large{applications}}};
+      \\
+    };
+
+    \path[->, very thick, draw=guixred1]<2->
+      (kernel) edge (initrd);
+    \path[->, very thick, draw=guixred1]<4->
+      (initrd) edge (shepherd);
+    \path[->, very thick, draw=guixred1]<6->
+      (shepherd) edge (user);
+    
+  \end{tikzpicture}
+  \end{overlayarea}
+
+  \begin{tikzpicture}[overlay,
+                      guile/.style = {
+                         fill=guixyellow, text=black, rotate=30,
+                         rounded corners=4mm, text width=3cm,
+                         opacity=.75, text opacity=1, text centered,
+                         minimum height=1.3cm
+                      }]
+    \node<3->(labelinitrd) [guile] at (initrd.east) {%
+      \Large{Guile}
+    };
+    \node<5->(labelinitrd) [guile] at (shepherd.east) {%
+      \Large{Guile}
+    };
+  \end{tikzpicture}
+\end{frame}
+
+\begin{frame}{}
+
+  \begin{textblock}{12}(2, 8)
+    \tiny{
+      Copyright \copyright{} 2010, 2012--2017 Ludovic Courtès \texttt{ludo@gnu.org}.\\[3.0mm]
+      GNU GuixSD logo, CC-BY-SA 4.0, \url{https://gnu.org/s/guix/graphics}
+
+      Copyright of other images included in this document is held by
+      their respective owners.
+      \\[3.0mm]
+      This work is licensed under the \alert{Creative Commons
+        Attribution-Share Alike 3.0} License.  To view a copy of this
+      license, visit
+      \url{http://creativecommons.org/licenses/by-sa/3.0/} or send a
+      letter to Creative Commons, 171 Second Street, Suite 300, San
+      Francisco, California, 94105, USA.
+      \\[2.0mm]
+      At your option, you may instead copy, distribute and/or modify
+      this document under the terms of the \alert{GNU Free Documentation
+        License, Version 1.3 or any later version} published by the Free
+      Software Foundation; with no Invariant Sections, no Front-Cover
+      Texts, and no Back-Cover Texts.  A copy of the license is
+      available at \url{http://www.gnu.org/licenses/gfdl.html}.
+      \\[2.0mm]
+      % Give a link to the 'Transparent Copy', as per Section 3 of the GFDL.
+      The source of this document is available from
+      \url{http://git.sv.gnu.org/cgit/guix/maintenance.git}.
+    }
+  \end{textblock}
+\end{frame}
+
+\end{document}
+
+% Local Variables:
+% coding: utf-8
+% comment-start: "%"
+% comment-end: ""
+% ispell-local-dictionary: "american"
+% compile-command: "rubber --pdf talk.tex"
+% End: