Add system start-up files for "guix publish".

* .gitignore: add etc/guix-publish.conf and /etc/guix-publish.service.
* etc/guix-publish.conf.in: New file.
* etc/guix-publish.service.in: New file.
* nix/local.mk (etc/guix-%.service, etc/guix-%.conf): Generalized former
  build-rules for by using patterns.
  (nodist_systemdservice_DATA): Add etc/guix-publish.service, update
  comment.
  (nodist_upstartjob_DATA): Add etc/guix-publish.conf, update comment.
* doc/guix.texi (Invoking guix publish): Add description for enabling
  "guix publish" on host distros using the new files.

.gitignore

@@ -50,6 +50,8 @@
 /emacs/guix-helper.scm
 /etc/guix-daemon.conf
 /etc/guix-daemon.service
+/etc/guix-publish.conf
+/etc/guix-publish.service
 /guix-daemon
 /guix-register
 /guix/config.scm

doc/guix.texi

@@ -6055,6 +6055,30 @@ add a call to @code{guix-publish-service} in the @code{services} field
 of the @code{operating-system} declaration (@pxref{guix-publish-service,
 @code{guix-publish-service}}).
 
+If you are instead running Guix on a ``foreign distro'', follow these
+instructions:”
+
+@itemize
+@item
+If your host distro uses the systemd init system:
+
+@example
+# ln -s ~root/.guix-profile/lib/systemd/system/guix-publish.service \
+        /etc/systemd/system/
+# systemctl start guix-publish && systemctl enable guix-publish
+@end example
+
+@item
+If your host distro uses the Upstart init system:
+
+@example
+# ln -s ~root/.guix-profile/lib/upstart/system/guix-publish.conf /etc/init/
+# start guix-publish
+@end example
+
+@item
+Otherwise, proceed similarly with your distro's init system.
+@end itemize
 
 @node Invoking guix challenge
 @section Invoking @command{guix challenge}

etc/guix-publish.conf.in

@@ -0,0 +1,12 @@
+# This is a "job" for the Upstart init system to launch 'guix-daemon'.
+# Drop it in /etc/init to have 'guix-daemon' automatically started.
+
+description "Publish the GNU Guix store"
+
+start on runlevel [2345]
+
+stop on runlevel [016]
+
+task
+
+exec @bindir@/guix publish --user=nobody --port=8181

etc/guix-publish.service.in

@@ -0,0 +1,19 @@
+# This is a "service unit file" for the systemd init system to launch
+# 'guix publish'.  Drop it in /etc/systemd/system or similar to have
+# 'guix publish' automatically started.
+
+[Unit]
+Description=Publish the GNU Guix store
+
+[Service]
+ExecStart=@bindir@/guix publish --user=nobody --port=8181
+Environment=GUIX_LOCPATH=/root/.guix-profile/lib/locale
+RemainAfterExit=yes
+StandardOutput=syslog
+StandardError=syslog
+
+# See <https://lists.gnu.org/archive/html/guix-devel/2016-04/msg00608.html>.
+TasksMax=1024
+
+[Install]
+WantedBy=multi-user.target

nix/local.mk

@@ -183,26 +183,26 @@ endif BUILD_DAEMON_OFFLOAD
 nodist_libexec_SCRIPTS =			\
   %D%/scripts/guix-authenticate
 
-# The '.service' file for systemd.
+# The '.service' files for systemd.
 systemdservicedir = $(libdir)/systemd/system
-nodist_systemdservice_DATA = etc/guix-daemon.service
+nodist_systemdservice_DATA = etc/guix-daemon.service etc/guix-publish.service
 
-etc/guix-daemon.service: etc/guix-daemon.service.in	\
+etc/guix-%.service: etc/guix-%.service.in	\
 			 $(top_builddir)/config.status
 	$(AM_V_GEN)$(MKDIR_P) "`dirname $@`";				\
 	$(SED) -e 's|@''bindir''@|$(bindir)|' <				\
-	       "$(srcdir)/etc/guix-daemon.service.in" > "$@.tmp";	\
+	       "$(srcdir)/$<" > "$@.tmp";	\
 	mv "$@.tmp" "$@"
 
-# The '.conf' job for Upstart.
+# The '.conf' jobs for Upstart.
 upstartjobdir = $(libdir)/upstart/system
-nodist_upstartjob_DATA = etc/guix-daemon.conf
+nodist_upstartjob_DATA = etc/guix-daemon.conf etc/guix-publish.conf
 
-etc/guix-daemon.conf: etc/guix-daemon.conf.in	\
+etc/guix-%.conf: etc/guix-%.conf.in	\
 			 $(top_builddir)/config.status
 	$(AM_V_GEN)$(MKDIR_P) "`dirname $@`";				\
 	$(SED) -e 's|@''bindir''@|$(bindir)|' <				\
-	       "$(srcdir)/etc/guix-daemon.conf.in" > "$@.tmp";		\
+	       "$(srcdir)/$<" > "$@.tmp";		\
 	mv "$@.tmp" "$@"
 
 EXTRA_DIST +=					\