Hello,
Im still having this issue when running the app in beta in strict confinement gives me a permission denied to the serial port im trying to connect to.
If running in edge channel in --devmode the serial port works good. Any thoughts what could i be missing or why i keep getting serial port permission denied?
In devmode, the snap sandbox is effectively disabled so this gives the snap access to the system. In general, the snap system expects a serial port slot to be provided by an appropriate gadget snap - and these are only applicable on Ubuntu Core systems. For classic Ubuntu / other distros there is no standard way for an application level snap to be provided access to a non-hotplugged serial port - whilst you could perhaps use system-files to specify access to the device node on the file-system, the snap would still likely not be able to access it since the device node would not be present in the snap’s device-cgroup.
So since you are not using a hotpluggable serial port, your use-case sounds more like a kiosk-type device on known hardware - in which case I think using Ubuntu Core would be more appropriate and hence then a custom gadget snap which can declare the serial-port slot for this device node would be the best approach.
Hi all, I work with @dguerrero5. All of these suggestions have been great.
couple of questions:
Regarding classic confinement, there is the Process for reviewing classic confinement snaps which will give you some idea of what that looks like - basically to be granted this, a snap must both require it in order to function (ie it is not possible to get it working under strict confinement at all) and the snap must fit within one of the existing supported categories for classic confinement. However, I think unforunately this snap may not meet the second criteria since I don’t think requiring access to a particular hardware device is not a supported category.
Also if your snap is in the public store, whilst it may not be intended for use by others, they could still install it.
As I suggested above, I really do feel like this sounds like a great use case for Ubuntu Core rather than classic Ubuntu (or some other Linux) since then you can prepare a custom image for the device which contains your own custom gadget snap which in-turn defines an appropriate serial-port slot to provide access to /dev/ttyS0 for your snap. See Building a gadget snap | Ubuntu which mentions the 64-bit PC Gadget Snap which sounds like it would be a good basis to work from in your case.
Beyond that, perhaps @ogra may be able to provide further advice if needed 
Thanks @alexmurray! Totally get public can install it, but it doesn’t do anything without registration in our system. This snap is being installed in old ‘arcade’ cabinets with antiquated monitors, etc most of which are unknown to us. While it certainly fits the ‘kiosk’ concept, the hardware involved is largely unknown. Having a full linux install is important so that he owner/operators of these cabinets can troubleshoot their issues.
As for the gadget snap idea, my concern is that it’s a suggestion, not declarative as to what we should be doing. Maybe it’s just how I’m reading it? My fear is the engineering cost/time to explore the suggestion only to be back where we are now if it doesn’t get the result we need. Make sense? We are letting electron-builder do a lot of the heavy lifting for us…
I’d be interested in what @ogra thinks as well. Happy to book either of you for consulting hours as this is a little out of our wheelhouse.
@TeamRBDG out of interest, could you please provide the output of the following on one of these machines? Thanks (I am wondering whether we may be able to revive https://github.com/snapcore/snapd/pull/7261 which could then allow snapd to support PCI-based serial-ports for hotplug - and so this should be enough to indicate whether in your case you are using such a device and then if this could support your use-case).
udevadm info /dev/ttyS0
@alexmurray See @dguerrero5 post above. I’ve also ordered the adaptor you recommended to at least say we tried that route.
Hmm since I don’t see something like:
Here I attach an image of the output.
E: ID_BUS=pci
Then I don’t think the PR I linked to above would help in this case (although since it looks like you are using VirtualBox I assume this is a virtual serial port). Can you provide more details on what your hardware setup is?
Also if you manage to have success using a USB-Serial adapter please let us know too. Thanks.
its actually not running in virtualbox, @dguerrero5 pulled that from his dev machine not from the actual device. below is from the cabinet:
Hi @TeamRBDG I am checking on the status of this request. I see revisions of network-sports-icarus successfully published one day ago, so are you still having issues with making this snap properly work? Thanks!
@TeamRBDG - since we’ve not heard back from you, we are removing this request from our review queue. When you have more time to respond, simply do so here and we can add the request back to the queue. Thanks
