What could be causing TeXLive packages to update without explicit user intervention?

Question

Up until now I was under the impression that TeXLive's packages only updated when you invoked tlmgr update ....

But today I noticed, for the first time, that some other process is definitely updating TeXLive packages. But I have not been able to identify which. So I'm looking for advice on how to determine what is causing these updates, and possibly help on how to stop these auto-updates from happening. More details below if you'd like to read on ;-)

TLDR: TeXLive packages auto-update on irregular intervals by some mysterious process. One of these updates left me with a broken install, and now I'd like to be able to disable any auto-updates of TeXLive.

I have installed TeXLive 2020 on Ubuntu 18.04.5. I also have an old 2019 installation still in place, but all paths are since long correctly set for TL2020. I installed and maintain TeXLive (in fact, the whole system) using Ansible (I haven't made those playbooks public yet because reasons, but if you think it helps trouble-shooting this issue, I'd be happy to share the relevant parts with you).

How do I know for sure that TeXLive's packages have been updated?
Well, after a recompilation of the exact same LaTeX document (on the same git commit, clean repo) suddenly failed the second time around with an error about filehook-2019.sty not found, which made no sense, I looked for any files in the TeXLive tree that had been updated recently (i.e., today) and found a bunch, most notably (showing a selection):

$ find /usr/local/texlive -newermt "2020-12-16"
/usr/local/texlive/2020/texmf-var/web2c/tlmgr.log
/usr/local/texlive/2020/texmf-dist/doc/latex/filehook
/usr/local/texlive/2020/texmf-dist/tex/latex/filehook
/usr/local/texlive/2020/texmf-dist/source/latex/filehook
/usr/local/texlive/2020/tlpkg/tlpobj/filehook.tlpobj
/usr/local/texlive/2020/tlpkg/backups/filehook.r56291.tar.lz4
/usr/local/texlive/2020/tlpkg/backups/...

The clincher was the contents of the tlmgr.log file (again, only showing select parts):

[Sun Nov 29 04:34:29 2020] update: bookcover (46410 -> 56947)
[Tue Dec 15 21:27:05 2020] update: beamer (55908 -> 57140)
[Tue Dec 15 23:11:08 2020] update: decision-table (56164 -> 57094)
[Tue Dec 15 23:11:08 2020] update: denisbdoc (55474 -> 56664)
[Wed Dec 16 02:41:56 2020] update: fgruler (42966 -> 56854)
[Wed Dec 16 02:41:57 2020] update: filehook (56291 -> 56479)

The timings of these updates suggests that they are unrelated to my activities (which involves running latexmk, lualatex, knitr::knit()). Also, it's not an update of all available TeXLive packages, just a small subset, which I could confirm by running tlmgr update --self --all myself a short while later, which updated around 100 packages and after which my LaTeX document compiled just fine again.

I have read the relevant parts of the TeXLive and tlmgr documentation, but found no mention of auto-updates.

On my machine, I have checked the user and system cron-jobs, and found nothing that pertains to tlmgr. I also checked the systemd jobs, ditto.

If by chance it's not tlmgr that's causing these updates, then what could it be? I also have R installed on this machine (I regularly knit Rnw/Rmd documents) which includes the tinytex R package, which I know contains a wrapper for tlmgr. But unless these are being activated on some schedule, or are invoked when knitr::knit() is called, I don't see how they are the culprits (also, I run knitr::knit() almost daily, and TeXLive package auto-updates appear to happen on much longer intervals as the log file shows).

Answer 1

When compiling .Rnw or .Rmd documents to PDF, the R function tinytex::latexmk() is called, which tries to install missing LaTeX packages by default. This behavior can be disabled via the option:

options(tinytex.install_packages = FALSE)

Before trying to install missing LaTeX packages, it will try to run tlmgr update --self --all. This is most likely to be the cause of the problem you observed.