Unclear how to change temp dir for shiny-server

[burgerga]

Currently shiny-server creates tempdirs in /tmp and it is unclear how to change this:

• It is not a config option (AFAIK based on the documentation)

• The only time /tmp is in the documentation is at the bottom of https://docs.rstudio.com/shiny-server/#running-shiny-server-with-root-privileges, there it says

  Finally, if the directory /tmp/shiny-server/ exists, it (and all files within it) should be owned by the user you specify.

  However, this directory (even if I create it) is not used by shiny-server

• So my next thought was setting an environment variable, so I used the instructions at https://docs.rstudio.com/shiny-server/#environment-variable-settings to set TMPDIR=/tmp/shiny-server, but shiny-server ignores this
• After some googling, creating an .Renviron in my shiny app with TMPDIR successfully changed the temp dir for that app only
• So finally, by creating /home/shiny/.Renviron I was able to fix the temp dir for all apps on shiny-server

Can this be made more clear in the documentation? (and maybe the tmpdir should be a configuration option? (I am using it on our server to give shiny app authors read access to this tmpdir by setting the setgid bit on that directory))

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PS Regarding https://docs.rstudio.com/shiny-server/#environment-variable-settings, the recommended way of changing these systemd files is with

systemctl edit shiny-server.service

this will leave the (shiny-server package maintained) /etc/systemd/system/shiny-server.service untouched, but creates override conf files in /etc/systemd/system/shiny-server.service.d/ (see https://serverfault.com/a/840999).