services: Add Singularity.

* gnu/packages/linux.scm (singularity)[source](snippet): Change file
name of setuid helpers in libexec/cli/*.exec.
[arguments]: Remove "--disable-suid".
* gnu/services/docker.scm (%singularity-activation): New variable.
(singularity-setuid-programs): New procedure.
(singularity-service-type): New variable.
* gnu/tests/singularity.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (Miscellaneous Services): Document it.

doc/guix.texi

@@ -24090,7 +24090,7 @@ The following is an example @code{dicod-service} configuration.
 @cindex Docker
 @subsubheading Docker Service
 
-The @code{(gnu services docker)} module provides the following service.
+The @code{(gnu services docker)} module provides the following services.
 
 @defvr {Scheme Variable} docker-service-type
 
@@ -24163,6 +24163,17 @@ The audit package to use.
 @end table
 @end deftp
 
+@defvr {Scheme Variable} singularity-service-type
+This is the type of the service that allows you to run
+@url{https://www.sylabs.io/singularity/, Singularity}, a Docker-style tool to
+create and run application bundles (aka. ``containers'').  The value for this
+service is the Singularity package to use.
+
+The service does not install a daemon; instead, it installs helper programs as
+setuid-root (@pxref{Setuid Programs}) such that unprivileged users can invoke
+@command{singularity run} and similar commands.
+@end defvr
+
 @node Setuid Programs
 @section Setuid Programs
 

gnu/local.mk

@@ -587,6 +587,7 @@ GNU_SYSTEM_MODULES =				\
   %D%/tests/networking.scm			\
   %D%/tests/rsync.scm				\
   %D%/tests/security-token.scm			\
+  %D%/tests/singularity.scm			\
   %D%/tests/ssh.scm				\
   %D%/tests/version-control.scm			\
   %D%/tests/virtualization.scm			\

gnu/packages/linux.scm

@@ -2899,12 +2899,16 @@ thanks to the use of namespaces.")
                   (substitute* "bin/singularity.in"
                     (("^PATH=.*" all)
                      (string-append "#" all "\n")))
+
+                  (substitute* (find-files "libexec/cli" "\\.exec$")
+                    (("\\$SINGULARITY_libexecdir/singularity/bin/([a-z]+)-suid"
+                      _ program)
+                     (string-append "/run/setuid-programs/singularity-"
+                                    program "-helper")))
                   #t))))
     (build-system gnu-build-system)
     (arguments
-     `(#:configure-flags
+     `(#:configure-flags '("--localstatedir=/var")
-       (list "--disable-suid"
-             "--localstatedir=/var")
        #:phases
        (modify-phases %standard-phases
          (add-after 'unpack 'patch-reference-to-squashfs-tools

gnu/services/docker.scm

@@ -24,12 +24,14 @@
   #:use-module (gnu services shepherd)
   #:use-module (gnu system shadow)
   #:use-module (gnu packages docker)
+  #:use-module (gnu packages linux)               ;singularity
   #:use-module (guix records)
   #:use-module (guix gexp)
   #:use-module (guix packages)
 
   #:export (docker-configuration
-            docker-service-type))
+            docker-service-type
+            singularity-service-type))
 
 ;;; We're not using serialize-configuration, but we must define this because
 ;;; the define-configuration macro validates it exists.
@@ -120,3 +122,60 @@ bundles in Docker containers.")
                   (service-extension account-service-type
                                      (const %docker-accounts))))
                 (default-value (docker-configuration))))
+
+
+;;;
+;;; Singularity.
+;;;
+
+(define %singularity-activation
+  (with-imported-modules '((guix build utils))
+    #~(begin
+        (use-modules (guix build utils))
+
+        (define %mount-directory
+          "/var/singularity/mnt/")
+
+        ;; Create the directories that Singularity 2.6 expects to find.  Make
+        ;; them #o755 like the 'install-data-hook' rule in 'Makefile.am' of
+        ;; Singularity 2.6.1.
+        (for-each (lambda (directory)
+                    (let ((directory (string-append %mount-directory
+                                                    directory)))
+                      (mkdir-p directory)
+                      (chmod directory #o755)))
+                  '("container" "final" "overlay" "session"))
+        (chmod %mount-directory #o755))))
+
+(define (singularity-setuid-programs singularity)
+  "Return the setuid-root programs that SINGULARITY needs."
+  (define helpers
+    ;; The helpers, under a meaningful name.
+    (computed-file "singularity-setuid-helpers"
+                   #~(begin
+                       (mkdir #$output)
+                       (for-each (lambda (program)
+                                   (symlink (string-append #$singularity
+                                                           "/libexec/singularity"
+                                                           "/bin/"
+                                                           program "-suid")
+                                            (string-append #$output
+                                                           "/singularity-"
+                                                           program
+                                                           "-helper")))
+                                 '("action" "mount" "start")))))
+
+  (list (file-append helpers "/singularity-action-helper")
+        (file-append helpers "/singularity-mount-helper")
+        (file-append helpers "/singularity-start-helper")))
+
+(define singularity-service-type
+  (service-type (name 'singularity)
+                (description
+                 "Install the Singularity application bundle tool.")
+                (extensions
+                 (list (service-extension setuid-program-service-type
+                                          singularity-setuid-programs)
+                       (service-extension activation-service-type
+                                          (const %singularity-activation))))
+                (default-value singularity)))

gnu/tests/singularity.scm

@@ -0,0 +1,128 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2019 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu tests singularity)
+  #:use-module (gnu tests)
+  #:use-module (gnu system)
+  #:use-module (gnu system vm)
+  #:use-module (gnu system shadow)
+  #:use-module (gnu services)
+  #:use-module (gnu services docker)
+  #:use-module (gnu packages bash)
+  #:use-module (gnu packages guile)
+  #:use-module (gnu packages linux)               ;singularity
+  #:use-module (guix gexp)
+  #:use-module (guix store)
+  #:use-module (guix grafts)
+  #:use-module (guix monads)
+  #:use-module (guix packages)
+  #:use-module (guix profiles)
+  #:use-module (guix scripts pack)
+  #:export (%test-singularity))
+
+(define %singularity-os
+  (simple-operating-system
+   (service singularity-service-type)
+   (simple-service 'guest-account
+                   account-service-type
+                   (list (user-account (name "guest") (uid 1000) (group "guest"))
+                         (user-group (name "guest") (id 1000))))))
+
+(define (run-singularity-test image)
+  "Load IMAGE, a Squashfs image, as a Singularity image and run it inside
+%SINGULARITY-OS."
+  (define os
+    (marionette-operating-system %singularity-os))
+
+  (define singularity-exec
+    #~(begin
+        (use-modules (ice-9 popen) (rnrs io ports))
+
+        (let* ((pipe (open-pipe* OPEN_READ
+                                 #$(file-append singularity
+                                                "/bin/singularity")
+                                 "exec" #$image "/bin/guile"
+                                 "-c" "(display \"hello, world\")"))
+               (str  (get-string-all pipe))
+               (status (close-pipe pipe)))
+          (and (zero? status)
+               (string=? str "hello, world")))))
+
+  (define test
+    (with-imported-modules '((gnu build marionette))
+      #~(begin
+          (use-modules (srfi srfi-11) (srfi srfi-64)
+                       (gnu build marionette))
+
+          (define marionette
+            (make-marionette (list #$(virtual-machine os))))
+
+          (mkdir #$output)
+          (chdir #$output)
+
+          (test-begin "singularity")
+
+          (test-assert "singularity exec /bin/guile (as root)"
+            (marionette-eval '#$singularity-exec
+                             marionette))
+
+          (test-equal "singularity exec /bin/guile (unprivileged)"
+            0
+            (marionette-eval
+             `(begin
+                (use-modules (ice-9 match))
+
+                (match (primitive-fork)
+                  (0
+                   (dynamic-wind
+                     (const #f)
+                     (lambda ()
+                       (setgid 1000)
+                       (setuid 1000)
+                       (execl #$(program-file "singularity-exec-test"
+                                              #~(exit #$singularity-exec))
+                              "test"))
+                     (lambda ()
+                       (primitive-exit 127))))
+                  (pid
+                   (cdr (waitpid pid)))))
+             marionette))
+
+          (test-end)
+          (exit (= (test-runner-fail-count (test-runner-current)) 0)))))
+
+  (gexp->derivation "singularity-test" test))
+
+(define (build-tarball&run-singularity-test)
+  (mlet* %store-monad
+      ((_        (set-grafting #f))
+       (guile    (set-guile-for-build (default-guile)))
+       ;; 'singularity exec' insists on having /bin/sh in the image.
+       (profile  (profile-derivation (packages->manifest
+                                      (list bash-minimal guile-2.2))
+                                     #:hooks '()
+                                     #:locales? #f))
+       (tarball  (squashfs-image "singularity-pack" profile
+                                 #:symlinks '(("/bin" -> "bin")))))
+    (run-singularity-test tarball)))
+
+(define %test-singularity
+  (system-test
+   (name "singularity")
+   (description "Test Singularity container of Guix.")
+   (value (build-tarball&run-singularity-test))))