[bug#56677] [PATCH 0/2] environment: Add --emulate-fhs option.

[Ludovic Courtès]

Hi John,

John Kehayias <john.kehayias@protonmail.com> skribis:

> From de7ae9b203a65e1ec1b1429ca4076f3f91b1ae33 Mon Sep 17 00:00:00 2001
> From: John Kehayias <john.kehayias@protonmail.com>
> Date: Wed, 20 Jul 2022 23:46:45 -0400
> Subject: [PATCH] environment: Add '--emulate-fhs'.
>
> * guix/scripts/environment.scm (show-environment-options-help, %options): Add
> '--emulate-fhs'.
> (setup-fhs): New procedure.  Setup for the Filesystem Hierarchy Standard (FHS)
> container.  Defines and uses FHS-SYMLINKS and LINK-CONTENTS to create FHS
> expected directories and creates /etc/ld.so.conf.
> (launch-environment): Add 'emulate-fhs?' key and implement it to set $PATH and
> generate /etc/ld.so.cache before calling COMMAND.
> (launch-environment/container): Add 'emulate-fhs?' and 'setup-hook' keys and
> implement them.  Define and use FHS-MAPPINGS, to set up additional bind mounts
> in the container to follow FHS expectations.
> (guix-environment*): Add glibc-for-fhs to the container packages when
> 'emulate-fhs?' key is in OPTS.
> * doc/guix.texi (Invoking guix shell): Document '--emulate-fhs'.
> (Invoking guix environment): Document '--emulate-fhs'.
> * tests/guix-environment-container.sh: Add tests for '--emulate-fhs'.

This new version of the patch looks great to me!

I applied it and took the liberty to make the changes below; let me know
if anything’s amiss.

Pushed together with a news entry:

  2c11e857af news: Add entry for 'guix shell --emulate-fhs'.
  c7ba5f38b8 environment: Add '--emulate-fhs'.
  3d1d29e440 gnu: Add glibc-for-fhs.

Thanks a lot for your work and for your patience!

Ludo’.

diff --git a/doc/guix.texi b/doc/guix.texi
index 43dfdd64f2..8803353f24 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -6196,21 +6196,26 @@ directory:
 guix shell --container --expose=$HOME=/exchange guile -- guile
 @end example
 
+@cindex file system hierarchy standard (FHS)
+@cindex FHS (file system hierarchy standard)
 @item --emulate-fhs
-@item -F
-For containers, emulate a Filesystem Hierarchy Standard (FHS)
-configuration within the container, see
-@uref{https://refspecs.linuxfoundation.org/fhs.shtml, the official
-specification}.  As Guix deviates from the FHS specification, this
+@itemx -F
+When used with @option{--container}, emulate a
+@uref{https://refspecs.linuxfoundation.org/fhs.shtml, Filesystem
+Hierarchy Standard (FHS)} configuration within the container, providing
+@file{/bin}, @file{/lib}, and other directories and files specified by
+the FHS.
+
+As Guix deviates from the FHS specification, this
 option sets up the container to more closely mimic that of other
 GNU/Linux distributions.  This is useful for reproducing other
 development environments, testing, and using programs which expect the
 FHS specification to be followed.  With this option, the container will
-include a version of @code{glibc} which will read
-@code{/etc/ld.so.cache} within the container for the shared library
-cache (contrary to @code{glibc} in regular Guix usage) and set up the
-expected FHS directories: @code{/bin}, @code{/etc}, @code{/lib}, and
-@code{/usr} from the container's profile.
+include a version of glibc that will read
+@file{/etc/ld.so.cache} within the container for the shared library
+cache (contrary to glibc in regular Guix usage) and set up the
+expected FHS directories: @file{/bin}, @file{/etc}, @file{/lib}, and
+@file{/usr} from the container's profile.
 
 @item --rebuild-cache
 @cindex caching, of profiles
diff --git a/gnu/packages/base.scm b/gnu/packages/base.scm
index b566057b41..2a9f2f34fc 100644
--- a/gnu/packages/base.scm
+++ b/gnu/packages/base.scm
@@ -933,15 +933,15 @@ (define (linker-script? file)
 ;; in FHS containers.
 (define-public glibc-for-fhs
   (hidden-package
-   (package
-     (inherit glibc)
+   (package/inherit glibc
      (name "glibc-for-fhs")
      (source (origin (inherit (package-source glibc))
                      ;; Remove Guix's patch to read ld.so.cache from /gnu/store
                      ;; directories, re-enabling the default /etc/ld.so.cache
                      ;; behavior.
-                     (patches (delete (car (search-patches 
"glibc-dl-cache.patch"))
-                                      (origin-patches (package-source 
glibc)))))))))
+                     (patches
+                      (delete (search-patch "glibc-dl-cache.patch")
+                              (origin-patches (package-source glibc)))))))))
 
 ;; Below are old libc versions, which we use mostly to build locale data in
 ;; the old format (which the new libc cannot cope with.)
diff --git a/guix/scripts/environment.scm b/guix/scripts/environment.scm
index f5b417457d..cf99760859 100644
--- a/guix/scripts/environment.scm
+++ b/guix/scripts/environment.scm
@@ -475,10 +475,10 @@ (define* (launch-environment command profile manifest
      (catch 'system-error
        (lambda ()
          (when emulate-fhs?
-           ;; When running in a container with EMULATE-FHS?, supplement $PATH
+           ;; When running in a container with EMULATE-FHS?, override $PATH
            ;; (optional, but to better match FHS expectations), and generate
            ;; /etc/ld.so.cache.
-           (setenv "PATH" "/bin:/usr/bin:/sbin:/usr/sbin:$PATH")
+           (setenv "PATH" "/bin:/usr/bin:/sbin:/usr/sbin")
            (invoke "ldconfig" "-X"))
          (apply execlp program program args))
        (lambda _
@@ -687,12 +687,15 @@ (define* (launch-environment/container #:key command bash 
user user-mappings
 list of file system mappings, contains the user-specified host file systems to
 mount inside the container.  If USER is not #f, each target of USER-MAPPINGS
 will be re-written relative to '/home/USER', and USER will be used for the
-passwd entry.  When EMULATE-FHS?, set up the container to follow the
-Filesystem Hierarchy Standard and provide a glibc that reads the cache from
-/etc/ld.so.cache.  SETUP-HOOK is an additional setup procedure to be called, 
as a
-list with the function name and arguments, currently only used with the
-EMULATE-FHS? option.  LINK-PROFILE? creates a symbolic link from
-~/.guix-profile to the environment profile.
+passwd entry.
+
+When EMULATE-FHS?, set up the container to follow the Filesystem Hierarchy
+Standard and provide a glibc that reads the cache from /etc/ld.so.cache.
+SETUP-HOOK is an additional setup procedure to be called, currently only used
+with the EMULATE-FHS? option.
+
+LINK-PROFILE? creates a symbolic link from ~/.guix-profile to the
+environment profile.
 
 Preserve environment variables whose name matches the one of the regexps in
 WHILE-LIST."
@@ -801,11 +804,9 @@ (define fhs-mappings
             (mkdir-p home-dir)
             (setenv "HOME" home-dir)
 
-            ;; Call an additional setup procedure, if provided.  Currently
-            ;; this is only used with the EMULATE-FHS? option, but could be
-            ;; expanded to a general list of functions to be called.
-            (if setup-hook
-                (apply (car setup-hook) (cdr setup-hook)))
+            ;; Call an additional setup procedure, if provided.
+            (when setup-hook
+              (setup-hook profile))
 
             ;; If requested, link $GUIX_ENVIRONMENT to $HOME/.guix-profile;
             ;; this allows programs expecting that path to continue working as
@@ -1113,9 +1114,9 @@ (define manifest
                                                     #:network? network?
                                                     #:map-cwd? (not no-cwd?)
                                                     #:emulate-fhs? emulate-fhs?
-                                                    #:setup-hook (if 
emulate-fhs?
-                                                                     (list 
setup-fhs profile)
-                                                                     #f))))
+                                                    #:setup-hook
+                                                    (and emulate-fhs?
+                                                         setup-fhs))))
 
                    (else
                     (return
diff --git a/tests/guix-environment-container.sh 
b/tests/guix-environment-container.sh
index 31e409420f..898c57f41b 100644
--- a/tests/guix-environment-container.sh
+++ b/tests/guix-environment-container.sh
@@ -230,4 +230,4 @@ guix environment -C --emulate-fhs --ad-hoc --bootstrap 
guile-bootstrap \
 
 # Test that the ld cache was generated and can be successfully read.
 guix environment -C --emulate-fhs --ad-hoc --bootstrap guile-bootstrap \
-     -- guile -c '(exit (execlp "ldconfig" "-p"))'
+     -- guile -c '(execlp "ldconfig" "ldconfig" "-p")'