problems with local user format files

[Karl Berry]

    Well it happens, and quite regularly. 

Ulrike, if you look at
/usr/local/texlive/dev/texmf-var/web2c/tlmgr-commands.log (that is,
wherever your TEXMFSYSVAR is; .../dev is my test tree), it should be
reporting exactly what command was run and exactly where the .fmt was
installed.

[Thu Oct 15 00:19:34 2020] running fmtutil-sys --no-error-if-no-engine=luajithbtex,luajittex,mfluajit --byfmt eplain
[Thu Oct 15 00:19:36 2020] success, output:
fmtutil: fmtutil is using the following fmtutil.cnf files (in precedence order):
.. lots of output ...
fmtutil [INFO]: log file copied to: /usr/local/texlive/dev/texmf-var/web2c/pdftex/eplain.log
fmtutil [INFO]: /usr/local/texlive/dev/texmf-var/web2c/pdftex/eplain.fmt installed.
..

If the user TEXMFVAR shows up there, perhaps a clue can be garnered. If
it doesn't show up, then fmtutil-user must be getting invoked by
something other than tlmgr. BTW, in my test installation, which I never
touch except to run tlmgr update --all nightly, I have never had a .fmt
created in TEXMFVAR. Puzzling.


Norbert: what I've always missed in tlmgr-commands.log (and its
predecessors :) is a line that straightforwardly says "rebuilding
foo.fmt due to update of package bar", or whatever the reason is for the
fmt update. I mean, tlmgr must know why it's calling
fmtutil. Unfortunately I've never looked into adding it myself and now I
am tied up with TUGboat et al. for the foreseeable future. Wdyt?

Thanks,
Karl