Re: successful installation, but problems updating

[Chris Marusich <cmmarusich@gmail.com>]

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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.

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've attached a patch which tries to clarify this in the manual.  What
do you think of it?

-- 
Chris

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From ce8c53bffa2f79f680f9b27bcb494a4fadb4038c Mon Sep 17 00:00:00 2001
From: Chris Marusich <cmmarusich@gmail.com>
Date: Fri, 10 Nov 2017 15:19:16 -0800
Subject: [PATCH] doc: Clarify the --fallback option.

* doc/guix.texi (Common Build Options): Describe --fallback in more detail.
  In particular, call out the fact that local builds can still happen even
  when --fallback is omitted.
---
 doc/guix.texi | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index b7f4f88f9..40705c4b8 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -5159,7 +5159,13 @@ Do not build the derivations.
 
 @item --fallback
 When substituting a pre-built binary fails, fall back to building
-packages locally.
+locally.  This affects behavior only when substitutes are enabled and
+Guix is building a derivation for which a substitute is known.  When
+@code{--fallback} is omitted, the build will fail if substitution fails.
+However, when @code{--fallback} is given, Guix will try to build the
+derivation locally if substitution fails.  When substitutes are not
+enabled or Guix is building a derivation for which a substitute is not
+known, a local build will always be performed.
 
 @item --substitute-urls=@var{urls}
 @anchor{client-substitute-urls}
-- 
2.14.2


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