Re: successful installation, but problems updating

[myglc2 <myglc2@gmail.com>]

On 11/10/2017 at 15:30 Chris Marusich writes:

> Hi Leo,
>
> Leo Famulari <leo@famulari.name> writes:
>
>> Substition is considered to fail when Guix is expecting a substitute but
>> the server returns 404, 504, or some other unexpected problem occurs. It
>> is not considered to fail if the server initially reports that no
>> substitute is available.

Hi Leo, this is a wonderful clarification of behavior that has confused
me for 1.5 years!
>
> Thank you for the clarification.  This is what I did not understand.  I
> read the manual and got the impression that when --fallback has not been
> given, if a given substitute cannot be found (regardless of whether or
> not a substitute server claimed to provide one), then Guix will not
> build it.  I see now that my understanding was mistaken.

I had this mistaken impression too.
>
> I've attached a patch which tries to clarify this in the manual.  What
> do you think of it?

Hey Chris,

How about saying what Leo said right up front in the substitutes
section. This allows the --fallback addition to be more brief.

Rough draft below.

WDYT? - George

1 file changed, 9 insertions(+), 2 deletions(-)
doc/guix.texi | 11 +++++++++--

modified   doc/guix.texi
@@ -2120,6 +2120,13 @@ server.  We call these pre-built items @dfn{substitutes}---they are
 substitutes for local build results.  In many cases, downloading a
 substitute is much faster than building things locally.
 
+When substitutes are enabled (the default) and a substitute is not
+available the build will take place locally. If a substitute is
+available but substitution fails, e.g., the substitute server returns
+404, 504, times out, or some other unexpected problem occurs, guix stops
+and reports an error unless --fallback or --keep-going options are
+specified.
+
 Substitutes can be anything resulting from a derivation build
 (@pxref{Derivations}).  Of course, in the common case, they are
 pre-built package binaries, but source tarballs, for instance, which
@@ -5192,8 +5199,8 @@ derivations has failed.
 Do not build the derivations.
 
 @item --fallback
-When substituting a pre-built binary fails, fall back to building
-packages locally.
+Attempt to build locally instead of issuing an error when substitutes
+are enabled and the substitution of a pre-built binary fails.
 
 @item --substitute-urls=@var{urls}
 @anchor{client-substitute-urls}