From 2e6a16f2bdd32d9efc444285c559d1eac18212cc Mon Sep 17 00:00:00 2001
From: Graham Christensen <graham@grahamc.com>
Date: Mon, 12 Aug 2019 19:56:57 -0400
Subject: [PATCH 1/3] dockerTools: document extraCommands

---
 doc/functions/dockertools.xml | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/doc/functions/dockertools.xml b/doc/functions/dockertools.xml
index 3e9281557d511f..3e5b76756e2f64 100644
--- a/doc/functions/dockertools.xml
+++ b/doc/functions/dockertools.xml
@@ -316,6 +316,19 @@ hello        latest   de2bf4786de6   About a minute ago   25.2MB
      </para>
     </listitem>
    </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>extraCommands</varname> <emphasis>optional</emphasis>
+    </term>
+    <listitem>
+     <para>
+       Commands to run while building the final layer, without access
+       to most of the layer contents. Changes to this layer are "on top"
+       of all the other layers, so can create additional directories
+       and files.
+     </para>
+    </listitem>
+   </varlistentry>
   </variablelist>
 
   <section xml:id="dockerTools-buildLayeredImage-arg-contents">

From 8adaae2df21852806782e659947bd7e3ff86eee5 Mon Sep 17 00:00:00 2001
From: Graham Christensen <graham@grahamc.com>
Date: Mon, 12 Aug 2019 19:59:40 -0400
Subject: [PATCH 2/3] dockertools.buildLayeredImage: default layer count up to
 100

---
 doc/functions/dockertools.xml         | 5 ++++-
 pkgs/build-support/docker/default.nix | 7 ++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/doc/functions/dockertools.xml b/doc/functions/dockertools.xml
index 3e5b76756e2f64..e2ea2f7b976b63 100644
--- a/doc/functions/dockertools.xml
+++ b/doc/functions/dockertools.xml
@@ -312,7 +312,10 @@ hello        latest   de2bf4786de6   About a minute ago   25.2MB
       Maximum number of layers to create.
      </para>
      <para>
-      <emphasis>Default:</emphasis> <literal>24</literal>
+      <emphasis>Default:</emphasis> <literal>100</literal>
+     </para>
+     <para>
+      <emphasis>Maximum:</emphasis> <literal>125</literal>
      </para>
     </listitem>
    </varlistentry>
diff --git a/pkgs/build-support/docker/default.nix b/pkgs/build-support/docker/default.nix
index ae3d93ff3db392..83e21c8945dc51 100644
--- a/pkgs/build-support/docker/default.nix
+++ b/pkgs/build-support/docker/default.nix
@@ -291,9 +291,10 @@ rec {
     # Files to add to the layer.
     closure,
     configJson,
-    # Docker has a 42-layer maximum, we pick 24 to ensure there is plenty
-    # of room for extension
-    maxLayers ? 24
+    # Docker has a 125-layer maximum, we pick 100 to ensure there is
+    # plenty of room for extension.
+    # https://github.com/moby/moby/blob/b3e9f7b13b0f0c414fa6253e1f17a86b2cff68b5/layer/layer_store.go#L23-L26
+    maxLayers ? 100
   }:
     let
       storePathToLayer = substituteAll

From abf82a18fb22d4d2805f7d3985d484fbe133fb68 Mon Sep 17 00:00:00 2001
From: Graham Christensen <graham@grahamc.com>
Date: Thu, 15 Aug 2019 09:47:05 -0400
Subject: [PATCH 3/3] doc/functions/dockertools.xml: clarify that "Commands" 
 means shell commands

Co-Authored-By: Jon <jonringer@users.noreply.github.com>
---
 doc/functions/dockertools.xml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/functions/dockertools.xml b/doc/functions/dockertools.xml
index e2ea2f7b976b63..a284182bb047c1 100644
--- a/doc/functions/dockertools.xml
+++ b/doc/functions/dockertools.xml
@@ -325,7 +325,7 @@ hello        latest   de2bf4786de6   About a minute ago   25.2MB
     </term>
     <listitem>
      <para>
-       Commands to run while building the final layer, without access
+       Shell commands to run while building the final layer, without access
        to most of the layer contents. Changes to this layer are "on top"
        of all the other layers, so can create additional directories
        and files.