luatex – Using Pandoc/LaTeX on Docker with LuaLaTeX PDF Engine and TeX Gyre Fonts

luaotfloadluatexpandoc

Motivation

Original question from pandoc discuss.

To build an Docker image allowing pandoc --pdf-engine=lualatex test.md -o test.pdf with the source file test.md as follow:

---
mainfont: TeX Gyre Termes
---

Lorem ipsum ttt

Background info about pandoc's Docker image

The official Docker image pandoc/latex:latest installed TeXLive under /opt whose write access is reserved for root user. By default, a container is run with root.

$ docker run --rm --entrypoint="" pandoc/latex:latest sh -c 'whoami'
root

To run pandoc using Docker, converting README.md to README.pdf:

$ docker run --rm --volume "$(pwd):/data" --user $(id -u):$(id -g) \
pandoc/latex README.md -o README.pdf

source: pandoc installing #Docker

! $(pwd) takes everything in current directory to /data in the Docker container built from image pandoc/latex:latest, then the container runs pandoc README.md -o README.pdf with the user and group privileges in the base system, and ends, The output README.pdf remains after the container has ended. The --rm is included so that it's not recorded in the list of containers docker ps.

Background info about Docker's USER

To avoid running as root in a Docker container, one can specify the USER name in Dockerfile.

Question

I tried compiling test.md with my Dockerfile, which used the identity USER pptruser of a normal user, and I got an unhelpful message showing a "fatal error". To know more about the problem, I first converted test.md to test.tex locally with

$ pandoc -s test.md -o test.tex

before I compiled it with LuaLaTeX in the Docker container built with my Dockerfile.

$ docker run --rm --volume "$(pwd):/home/pptruser" --user $(id -u):$(id -g) \
customDockerImage:1.0 --pdf-engine=lualatex test.md -o test.pdf

This is LuaHBTeX, Version 1.12.0 (TeX Live 2020) 
 restricted system commands enabled.
(./201113-TAM-compte-rendu.tex
LaTeX2e <2020-10-01> patch level 2



luaotfload | load : FATAL ERROR
luaotfload | load :   × Failed to load "fontloader" module "basics-gen".
luaotfload | load :   × Error message:
luaotfload | load :     × "...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-init.lua:306: system : no writeable cache path, quiting".

stack traceback:
    ...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-main.lua:174: in local 'load_fontloader_module'
    ...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-init.lua:308: in upvalue 'init_main'
    ...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-init.lua:560: in function 'luaotfload-init.lua'
    ...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-main.lua:298: in field 'main'
    [\directlua]:1: in main chunk

...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-init.lua:306: system : no wr
iteable cache path, quiting
stack traceback:
    [C]: in function 'error'
    ...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-init.lua:306: in function '
os.exit'
    ...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-main.lua:177: in local 'loa
d_fontloader_module'
    ...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-init.lua:308: in upvalue 'i
nit_main'
    ...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-init.lua:560: in function '
luaotfload-init.lua'
    ...dir/texmf-dist/tex/luatex/luaotfload/luaotfload-main.lua:298: in field 'mai
n'
    [\directlua]:1: in main chunk.
<everyjob> ...ring \\def\string \\encodingdefault{OT1}')end }
                                                  \let \f@encoding \encoding...

l.1 
  % Options for packages loaded elsewhere

The no writeable cache path from luaotfload caused the error. I observed that if I remove the USER pptruser related settings and run everything as root, then the error is gone.

I wonder if there's a way to build a Dockerfile so that the compilation of test.md containing the font TeX Gyre Termes with LuaLaTeX PDf engine works.

Best Answer

The solution is incredible simple: identify the "writable cache path", and give it the write permission to everyone. In the Docker image, pandoc/latex:latest, it's /opt/texlive/texdir/texmf-var.

I resolved this issue at commit VincentTam/pandoc-mermaid-docker@d86343f0 on GitLab by appending

chmod o+w /opt/texlive/texdir/texmf-var

to the RUN command that created the user pptruser (somewhere before changing to a normal user from root).

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