The point is: If nodm was able to decrypt and log you in just after powering on the system, then any thief who got your hardware can do so. It might be possible to configure nodm todo so, but you would lose all security gained by encrypting your harddisk.

This might be related to the HP manager. Please see if you have CUPS installed, for example browse to localhost:631 and see if you can do something there.

I cant' help you with iOS stuff. But my understanding is that the .cer extension is only used by Microsoft. If the answers below do not help you, you might want to ask in an iOS programming related place.

Note that /tmp is mounted as tmpfs on many distributions, hence does not require diskspace. In particular this is the case on debian.

This does not really answer what you need: What is the purpose of the certificate you generate? Maybe an HTTPS server? Or personal authentication for some application? But I think you already got enough good answers below for what you asked.

I am no expert, but I fear this is firmware thing. It might be helpful to see if there is a solution for other operation systems.

According to support.ssl.com/Knowledgebase/Article/View/19/0/… .pem is an encoding and .cer is an extension. Shortly: a .cer file may contain both a PEM or a DER encoding. What exactly do you need? (The link should help you.)

Maybe you can post the script, the command to call the script and the command used in terminal?

Okay, I will remove that portability comment. Though your definition of recent seems to differ.

Not really. There is probably a more elegant solution for every script or programming language available.

You will need to store your presentation in a place where the linux machine can find it. For example an SMB share. If you can do that, you should mount that share under linux and you don't need to do any copying. Ideally all windows users would store the file in the same share, then no copying at all should be needed. You might still need to restart the presentation, but some presentation programs might be able to reload on a file change.