guix environment: error: cannot create container: unprivileged user cannot create user namespaces

[yasu <yasu@yasuaki.com>]

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Hi Guix Development,

I rely on the -C option below to compile ./pre-inst-env  .

guix environment -C guix


(I learned the technique through 
https://gitlab.com/pjotrp/guix-notes/blob/master/INSTALL.org - 
./pre-inst-env just won't compile correctly unless I follow the
instructions on the page)

However, this feature has become unavailable after the
commit  8bc5ca5160db...

~/co/guix (master)$ guix environment -C guix
guix environment: error: cannot create container: unprivileged user
cannot create user namespaces
guix environment: error: please set
/proc/sys/kernel/unprivileged_userns_clone to "1"



The commit details are below:
commit 8bc5ca5160db3d82bd5b6b2b7ed80c96f42bd33e
Author: Paul Garlick <pgarlick@tourbillion-technology.com>
Date:   Thu Dec 3 16:00:18 2020 +0000

    linux-container: Correct test for unprivileged user namespace
support.

    Fixes <https://bugs.gnu.org/31977>;;.
    Reported by Paul Garlick <pgarlick@tourbillion-technology.com>.

    * gnu/build/linux-container.scm (unprivileged-user-namespace-
supported?):
    Return #f when the 'userns-file' does not exist.

diff --git a/gnu/build/linux-container.scm b/gnu/build/linux-
container.scm
index 4a8bed5a9a..3870b50907 100644
--- a/gnu/build/linux-container.scm
+++ b/gnu/build/linux-container.scm
@@ -44,7 +44,7 @@
   (let ((userns-file "/proc/sys/kernel/unprivileged_userns_clone"))
     (if (file-exists? userns-file)
         (eqv? #\1 (call-with-input-file userns-file read-char))
-        #t)))
+        #f)))

 (define (setgroups-supported?)
   "Return #t if the setgroups proc file, introduced in Linux-libre
3.19,



I hope this is a bug that can be fixed.   Otherwise, it looks like I
won't  be able to compile pre-inst-env?

Cheers,
Yasu

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