Why same CUPS client to CUPS server have different AuthInfoRequired values in printers.conf file

[mdlueck]

I successfully set up Linux CUPS client connections to Linux CUPS server connections last when Xubuntu 20.04 was current. Now Xubuntu 24.04 is current. (So my Linux workstation has undergone now two LTS upgrades... 20.04 --> 22.04 --> 24.04

Then the CUPS client connections to shared printers ended up with:

AuthInfoRequired none

in the printers.conf file. Now on Xubuntu 24.04 building the same connections ends up with:

AuthInfoRequired username,password

in the local printers.conf file! Test print jobs never make it out of CUPS on the workstation.... the jobs are stalled requiring authentication.

Frustrated, I thought to set up a shared CUPS-PDF print share to parallel debug what was going on. I added that to the Linux server, marked it shared in the CUPS configuration. Then connected to it from my same Xubuntu 24.04 system... and that remote printer shows up with:

AuthInfoRequired none

in the local printers.conf file! Test print jobs successfully make it all the way through to the ~/PDF directory of my home directory on the Linux CUPS server. THAT is not even funny! Same CUPS server to same CUPS client, and just magically different printers end up with different AuthInfoRequired values in the client printers.conf file?! What is going on?

Today online I saw one suggestion to vaguely make changes to the workstation cupsd.conf file to adjust authentication. Nothing in the cupsd.conf file calls out per printer properties. So that does not explain why from the same client to the same server, different printers end up with a different value for AuthInfoRequired in the workstation's printers.conf file.

I do not see a way to define the AuthInfoRequired value through the GUI when adding a network printer. According to the comment header in the printers.conf file, the file is auto-generated. But from where does it get generated? Where is the source that insists on putting different values for the AuthInfoRequired property?

The goal is to have:

AuthInfoRequired none

result in the printers.conf file so that print jobs from any source application (Native Linux GUI, terminal programs, Wine programs, VirtualBox VM sessions... all sources of print jobs) running on the workstation may spool over and through to CUPS server shared printers. It is sufficient permissions that people can authenticate with the Linux login. Our environment does not need an authentication layer also in the printing system.

Please kindly advise.

I am thankful.
Michael Lueck

[mdlueck]

I finally figured out what was going on today. Pull up a chair....

As I was documenting the server steps... something jumped out at me this time. When I issued the command to stop the CUPS service, it nagged that CUPS socket was still running even though CUPS service had been successfully stopped. So I went on to find the correct syntax to make sure CUPS socket also came down on the server.

Xubuntu 24.04 was simple enough.

With everything CUPS related down, I set about hand adjusting the printers.conf entries on both CUPS server and CUPS client. I put:

AuthInfoRequired none

in both on the line between UUID and Info.

Then I restarted CUPS on the server, CUPS on the workstation.

I sent a test print expecting the:

AuthInfoRequired none

line to suddenly get switched back to userid / password.

Much to my shock right around lunch time, I got a print job to print on the server!

So I think....

When I started on CUPS back in 2004, perhaps the default for AuthInfoRequired if none present in the configuration file was AuthInfoRequired none, and then the default got changed to AuthInfoRequired userid / password... so if no line at all was found in the file, newer CUPS binaries assume AuthInfoRequired userid / password instead of AuthInfoRequired none.

I also suspect my not stopping CUPS.socket on the CUPS server while hand editing the CUPS configuration files was still enough CUPS running that I was not getting a clean read of the hand modified CUPS configuration files.

Can anyone speak to my two above conclusions of what was suddenly causing the trouble with desiring to use CUPS with AuthInfoRequired none?

I am thankful.
Michael Lueck

[michaelrsweet]

I'll look at the code but the default should still be "none". But I'm glad you were able to get things working...

[mdlueck]

Greetings Michael, Have you had opportunity to review the CUPS code and find anything that would explain the above mentioned behavior?

[michaelrsweet]

No.