Hi Leo,

 > I'd guess that Ubuntu, like Debian, by default disables the unprivileged
> creation of containers.
>
> What is the value of '/proc/sys/kernel/unprivileged_userns_clone'?

$ cat /proc/sys/kernel/unprivileged_userns_clone
1

> If you followed the instructions in the manual while installing Guix
> [0], then your daemon's socket should be in /var/guix. When building
> Guix from the Git checkout, did you set the value of localstatedir like
> this when configuring?
>
> $ ./configure --localstatedir=/var

No. I just followed the instructions under "contributing" blindly.

> If not, it defaults to '/usr/local'. If that's what happened, can you
> reconfigure as shown above, and try Ludo's command again?

I did:

$ ./configure --localstatedir=/var
$ make check

The environment test case still fails. Then again

[dev]$ ./pre-inst-env strace -f -s 234 -o log guix environment 
--container --ad-hoc --bootstrap guile-bootstrap -- guile -c '(exit 42)'
substitute: warning: failed to install locale: Invalid argument
substitute: updating list of substitutes from 
'https://mirror.hydra.gnu.org'... substitute: updating list of 
substitutes from 'https://mirror.hydra.gnu.org'... substitute: updating 
list of substitutes from 'https://mirror.hydra.gnu.org'... substitute: 
updating list of substitutes from 'https://mirror.hydra.gnu.org'... 100.0%
substitute: updating list of substitutes from 'https://hydra.gnu.org'... 
100.0%
The following derivations will be built:
    /gnu/store/n1mv18v7dvjx3zz6xwryqw6mvfjj68ls-profile.drv
    /gnu/store/90b3v64bp7rjpsd841bxflh7a2h544f9-module-import.drv
    /gnu/store/sc9w2yza3af4p0vjgkkwf7jmdh1m05n6-module-import-compiled.drv
The following file will be downloaded:
    /gnu/store/aiz8db2gni401wc9fgidmcggxyb1czis-guile-bootstrap-2.0
warning: failed to install locale: Invalid argument

Found valid signature for 
/gnu/store/aiz8db2gni401wc9fgidmcggxyb1czis-guile-bootstrap-2.0
 From 
https://mirror.hydra.gnu.org/nar/aiz8db2gni401wc9fgidmcggxyb1czis-guile-bootstrap-2.0
Downloading aiz8db...-guile-bootstrap-2.0 (12.1MiB installed)...
 
https://mirror.hydra.gnu.org/nar/aiz8db2gni401wc9fgidmcggxyb1czis-guile-bootstrap-2.0 
1.1MiB/s 00:03 | 3.4MiB transferred


No error message this time. The log is attached.

Konrad.