[cups-devel] [MOD] STR #4755: In auto-shutdown mode ("-l") with activated web interface keep scheduler only running when interactive CGI scripts are used

[Till Kamppeter]

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[STR New]

In the auto-shutdown mode ("-l") CUPS only shuts down on idle if the web
interface is de-activated ("WebInterface=no" in cupsd.conf). De-activating
the web interface does not only de-activates CUPS' built-in printer setup
tool and help system but also general download of files from CUPS. The file
download is needed by more applications then one thinks of, especially by
cupsctl or by apps which download PPD files of print queues via
http://<server>:631/printers/<printer>.ppd. cupsctl is even worse, as it
does not realize that it gets an error message HTML page from CUPS when
downloading cupsd.conf and after that writes cupsd.conf back, destroying
it.

So my quick-and-dirty approach for my mobile environment is to allow CUPS
to auto-shutdown when WebInterface=Yes is set. In my case it will be no
problem as I do not install the CGI scripts (/usr/lib/cups/cgi-bin/) on my
mobile device.

Generally I suggest to change the meaning of the WebInterface variable in
cupsd.conf, so that file download always works and "WebInterface=no" only
deactivates the CGI scripts. This way with activated CGI scripts
auto-shutdown is prevented so that the web wizards work correctly. With
de-activated web interface only the scripts are blocked and file downloads
stay working to assure that applications behave correctly.

Even better would be to make the CGI scripts/web wizards robust against
auto-shutdown of CUPS, simply continuing correctly when CUPS shuts down and
the next submission of a form fires up CUPS again.

Link: https://www.cups.org/str.php?L4755
Version: 2.1-current
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