05/05: reppar: Add note on OS kernel.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository maintenance.

commit 9141e7b0c54999a33fa2426a518e564370e9112f
Author: Ludovic Courtès <address@hidden>
Date:   Tue Jul 21 12:01:03 2015 +0200

    reppar: Add note on OS kernel.
---
 doc/reppar-2015/reproducible-hpc.skb |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/doc/reppar-2015/reproducible-hpc.skb 
b/doc/reppar-2015/reproducible-hpc.skb
index 6325be6..3bb587d 100644
--- a/doc/reppar-2015/reproducible-hpc.skb
+++ b/doc/reppar-2015/reproducible-hpc.skb
@@ -629,7 +629,16 @@ access to the Internet.  However, the daemon needs to be 
able to download
 source code tarballs or pre-built binaries from external servers.  Thus,
 the daemon must run on a node with Internet access, which could be
 contrary to the policy on some clusters.])
-
+      (p (emph [OS kernel.]) [ By choosing not to use a full-blown VM
+and thus relying on the host OS kernel, our system assumes that the
+kernel interface is stable and that the kernel has little or no impact
+on program behavior.  While this may sound like a broad assumption, our
+experience has shown that it holds for almost all the software packages
+provided by Guix.  Indeed, while applications may be sensitive to
+changes in the C library, only low-level kernel-specific user-land
+software is really sensitive to changes in the kernel.  The build daemon
+itself relies on features that have been available in the kernel for
+several years.])
       (p (emph [Non-determinism.])[ Despite the use of
 isolated containers to run build processes, there are still a few sources
 of non-determinism that build systems of packages might use and