From 0167b61ef45c3cf8223d67893956144c65d811bf Mon Sep 17 00:00:00 2001
From: Brian McKenna <brian@brianmckenna.org>
Date: Fri, 15 Apr 2016 21:46:42 +1000
Subject: [PATCH] dockerTools: only add "/nix" if it exists

The /nix path in 4d200538 of the layer tar didn't exist for some
packages, such as cacert. This is because cacert just creates an /etc
directory and doesn't depend on any other /nix paths. If we tried
putting this directory in the tar and using overlayfs with it, we'd get
"Invalid argument" when trying to remove the directory.

We now check whether the closure is non-empty before telling tar to
store the /nix directory.

Fixes #14710.
---
 pkgs/build-support/docker/default.nix | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/pkgs/build-support/docker/default.nix b/pkgs/build-support/docker/default.nix
index f874354b15ed..5ead82dee8b5 100644
--- a/pkgs/build-support/docker/default.nix
+++ b/pkgs/build-support/docker/default.nix
@@ -286,17 +286,20 @@ EOF
         cp ${layer}/* temp/
         chmod ug+w temp/*
 
-        # FIXME: might not be /nix/store
-        echo '/nix' >> layerFiles
-        echo '/nix/store' >> layerFiles
         for dep in $(cat $layerClosure); do
-          find $dep >> layerFiles
+          find $dep -path "${layer}" -prune -o -print >> layerFiles
         done
 
+        if [ -s layerFiles ]; then
+          # FIXME: might not be /nix/store
+          echo '/nix' >> layerFiles
+          echo '/nix/store' >> layerFiles
+        fi
+
         echo Adding layer
         tar -tf temp/layer.tar >> baseFiles
         sed 's/^\.//' -i baseFiles
-        comm <(sort -n baseFiles|uniq) <(sort -n layerFiles|uniq|grep -v ${layer}) -1 -3 > newFiles
+        comm <(sort -u baseFiles) <(sort -u layerFiles) -1 -3 > newFiles
         tar -rpf temp/layer.tar --mtime=0 --no-recursion --files-from newFiles 2>/dev/null || true
 
         echo Adding meta