Build AppImage and linux binary using Ubuntu 18.04 (fixes #1068)

This is needed to get an old enough version of glibc to run the Linux
binary as an AWS Lambda layer and to support some versions of CentOS.

1 files changed, 9 insertions, 3 deletions

diff --git a/appimage/Dockerfile b/appimage/Dockerfile
index c1914144..24c9c672 100644
--- a/appimage/Dockerfile
+++ b/appimage/Dockerfile
@@ -1,13 +1,19 @@
-FROM ubuntu:20.04
+FROM ubuntu:18.04
 ENV DEBIAN_FRONTEND=noninteractive
 RUN apt-get update
 RUN apt-get -y install screen git sudo \
-    build-essential pkg-config cmake \
+    build-essential pkg-config \
     zlib1g-dev libjpeg-dev libgnutls28-dev \
     python3-pip texlive-latex-extra latexmk \
     inkscape imagemagick busybox-static wget fuse && \
     apt-get clean && rm -rf /var/lib/apt/lists/*
-RUN pip3 install sphinx sphinx_rtd_theme
+# Get cmake from pypi. We need to keep Ubuntu 18.04 for a while longer
+# since the glibc in Ubuntu 20.04 is too new (as of late 2023) for
+# Amazon Linux 2 in Lambda and for some supported CentOS versions.
+# When we are ready to update to 20.04 or newer, remove the version
+# constraint on sphinx, and install the OS package for cmake.
+RUN pip3 install --upgrade pip
+RUN pip3 install sphinx==4 sphinx_rtd_theme cmake
 COPY entrypoint /entrypoint
 RUN chmod +x /entrypoint
 ENTRYPOINT [ "/entrypoint" ]