diff --git a/automation/build/archlinux/current.dockerfile b/automation/build/archlinux/current.dockerfile
index d8fbebaf79..d46fc9d9ca 100644
--- a/automation/build/archlinux/current.dockerfile
+++ b/automation/build/archlinux/current.dockerfile
@@ -20,6 +20,7 @@ RUN pacman -S --refresh --sysupgrade --noconfirm --noprogressbar --needed \
         iasl \
         inetutils \
         iproute \
+        # lib32-glibc for Xen < 4.15
         lib32-glibc \
         libaio \
         libcacard \
diff --git a/automation/build/centos/7.2.dockerfile b/automation/build/centos/7.2.dockerfile
index c2f46b694c..af672a0be1 100644
--- a/automation/build/centos/7.2.dockerfile
+++ b/automation/build/centos/7.2.dockerfile
@@ -34,6 +34,7 @@ RUN rpm --rebuilddb && \
         yajl-devel \
         pixman-devel \
         glibc-devel \
+        # glibc-devel.i686 for Xen < 4.15
         glibc-devel.i686 \
         make \
         binutils \
diff --git a/automation/build/centos/7.dockerfile b/automation/build/centos/7.dockerfile
index e37d9d743a..5f83c97d0c 100644
--- a/automation/build/centos/7.dockerfile
+++ b/automation/build/centos/7.dockerfile
@@ -32,6 +32,7 @@ RUN yum -y install \
         yajl-devel \
         pixman-devel \
         glibc-devel \
+        # glibc-devel.i686 for Xen < 4.15
         glibc-devel.i686 \
         make \
         binutils \
diff --git a/automation/build/debian/jessie.dockerfile b/automation/build/debian/jessie.dockerfile
index 1232b9e204..808d6272e4 100644
--- a/automation/build/debian/jessie.dockerfile
+++ b/automation/build/debian/jessie.dockerfile
@@ -31,6 +31,7 @@ RUN apt-get update && \
         bin86 \
         bcc \
         liblzma-dev \
+        # libc6-dev-i386 for Xen < 4.15
         libc6-dev-i386 \
         libnl-3-dev \
         ocaml-nox \
diff --git a/automation/build/debian/stretch.dockerfile b/automation/build/debian/stretch.dockerfile
index 32742f7f39..e3bace1f87 100644
--- a/automation/build/debian/stretch.dockerfile
+++ b/automation/build/debian/stretch.dockerfile
@@ -32,6 +32,7 @@ RUN apt-get update && \
         bin86 \
         bcc \
         liblzma-dev \
+        # libc6-dev-i386 for Xen < 4.15
         libc6-dev-i386 \
         libnl-3-dev \
         ocaml-nox \
diff --git a/automation/build/debian/unstable.dockerfile b/automation/build/debian/unstable.dockerfile
index aeb4f3448b..9a10ee08d6 100644
--- a/automation/build/debian/unstable.dockerfile
+++ b/automation/build/debian/unstable.dockerfile
@@ -32,6 +32,7 @@ RUN apt-get update && \
         bin86 \
         bcc \
         liblzma-dev \
+        # libc6-dev-i386 for Xen < 4.15
         libc6-dev-i386 \
         libnl-3-dev \
         ocaml-nox \
diff --git a/automation/build/fedora/29.dockerfile b/automation/build/fedora/29.dockerfile
index 6a4e5b0413..5482952523 100644
--- a/automation/build/fedora/29.dockerfile
+++ b/automation/build/fedora/29.dockerfile
@@ -25,6 +25,7 @@ RUN dnf -y install \
         yajl-devel \
         pixman-devel \
         glibc-devel \
+        # glibc-devel.i686 for Xen < 4.15
         glibc-devel.i686 \
         make \
         binutils \
diff --git a/automation/build/suse/opensuse-leap.dockerfile b/automation/build/suse/opensuse-leap.dockerfile
index c60c13c943..685dd5d7fd 100644
--- a/automation/build/suse/opensuse-leap.dockerfile
+++ b/automation/build/suse/opensuse-leap.dockerfile
@@ -26,6 +26,7 @@ RUN zypper install -y --no-recommends \
         git \
         glib2-devel \
         glibc-devel \
+        # glibc-devel-32bit for Xen < 4.15
         glibc-devel-32bit \
         gzip \
         hostname \
diff --git a/automation/build/suse/opensuse-tumbleweed.dockerfile b/automation/build/suse/opensuse-tumbleweed.dockerfile
index 084cce0921..061173e751 100644
--- a/automation/build/suse/opensuse-tumbleweed.dockerfile
+++ b/automation/build/suse/opensuse-tumbleweed.dockerfile
@@ -26,6 +26,7 @@ RUN zypper install -y --no-recommends \
         git \
         glib2-devel \
         glibc-devel \
+        # glibc-devel-32bit for Xen < 4.15
         glibc-devel-32bit \
         gzip \
         hostname \
diff --git a/automation/build/ubuntu/bionic.dockerfile b/automation/build/ubuntu/bionic.dockerfile
index 712b2e4722..408063698c 100644
--- a/automation/build/ubuntu/bionic.dockerfile
+++ b/automation/build/ubuntu/bionic.dockerfile
@@ -32,6 +32,7 @@ RUN apt-get update && \
         bin86 \
         bcc \
         liblzma-dev \
+        # libc6-dev-i386 for Xen < 4.15
         libc6-dev-i386 \
         libnl-3-dev \
         ocaml-nox \
diff --git a/automation/build/ubuntu/focal.dockerfile b/automation/build/ubuntu/focal.dockerfile
index c1c1f8d58f..90b4001a6a 100644
--- a/automation/build/ubuntu/focal.dockerfile
+++ b/automation/build/ubuntu/focal.dockerfile
@@ -31,6 +31,7 @@ RUN apt-get update && \
         bin86 \
         bcc \
         liblzma-dev \
+        # libc6-dev-i386 for Xen < 4.15
         libc6-dev-i386 \
         libnl-3-dev \
         ocaml-nox \
diff --git a/automation/build/ubuntu/trusty.dockerfile b/automation/build/ubuntu/trusty.dockerfile
index 397a28061d..fd377d948f 100644
--- a/automation/build/ubuntu/trusty.dockerfile
+++ b/automation/build/ubuntu/trusty.dockerfile
@@ -32,6 +32,7 @@ RUN apt-get update && \
         bin86 \
         bcc \
         liblzma-dev \
+        # libc6-dev-i386 for Xen < 4.15
         libc6-dev-i386 \
         libnl-3-dev \
         ocaml-nox \
diff --git a/automation/build/ubuntu/xenial.dockerfile b/automation/build/ubuntu/xenial.dockerfile
index ce0e84fa2f..57a71eb8c6 100644
--- a/automation/build/ubuntu/xenial.dockerfile
+++ b/automation/build/ubuntu/xenial.dockerfile
@@ -32,6 +32,7 @@ RUN apt-get update && \
         bin86 \
         bcc \
         liblzma-dev \
+        # libc6-dev-i386 for Xen < 4.15
         libc6-dev-i386 \
         libnl-3-dev \
         ocaml-nox \