How does _OpenCPN_SILock work?

[jimseng]

Hello.
If I pull the power on the Raspberry pi, or reboot without shutting down OpenCPN then I get the safe mode dialog box. I believe this is something to do with _OpenCPN_SILock but I can't figure out how it works? I have looked at the attributes of the file etc. Can someone enlighten me? I have a python Tkinter app to manage the launching and shutting down of OpenCPN and the pi but I want to see if I can mitigate for a bad shutdown. Ideally I would find out if there was a clean shutdown or not on boot and take action if not. Mostly it revolves around having a backup opencpn.conf file at the ready.
Thanks

[Hakan]

To not risk damage files it's vital to close OCPN before power off, correct.
Maybe you can use something like this to close from a script:
pi@RPi4:~ $ ps -C opencpn
PID TTY TIME CMD
1500 ? 12:07:43 opencpn
pi@RPi4:~ $ kill -s SIGUSR1 1500
If no answer for opencpn it's closed and you can power off.
But Linux is not my native world so there may be better ways.

[jimseng]

I already do close it with python. I'm asking what if the power goes by mistake. Or more to the point. How does OpentCPN know it has been brutally shut down?

[wholybee]

Originally Posted by jimseng

I already do close it with python. I'm asking what if the power goes by mistake. Or more to the point. How does OpentCPN know it has been brutally shut down?

OpenCPN saves its state and all it's files when it shuts down. If it doesn't shut down properly, it looses changes to those files, any configuration changes you made, changes to chart display, preferences, etc. are all lost. Those changes are not saved when you make them, they are saved when OCPN shuts down.

I'm not sure exactly, but I assume it is the state of these files how OCPN knows it did not shut down.

How often does your system shutdown unexpectedly? It was maybe a once a year occurrence on my circumnavigation, with passages as long as 30 days. Running 24/7 on a windows laptop. If it happens often enough to be an issue, I would worry less about the dialog, and more about the reliability of your system.

[jimseng]

I'm in the process of putting a system together. I know it's the file opencpn.conf that gets saved when OpenCPN is closed properly. I'm looking at all possibilities scenarios, one of which is that someone might shutdown/reboot/isolate the batteries/a fuse might blow etc. I'm specifically after the technical reason how OpenCPN can tell it hasn't been closed correctly.

[bdbcat]

To answer the OP's question:


1. OCPN creates the _OpenCPN_SILock when it starts up normally.
2. As one of the very last things OCPN does on a normal clean shutdown, he deletes the _OpenCPN_SILockfile.


So, if you are planning to "pull the rug" from under OCPN, in your script you could delete the lock file. OCPN will start normally next time, with or without corrupted files.


Good Luck
Dave

[jimseng]

That's what I thought Dave, hence the subject. However it seems not to be the case. _OpenCPN_SILock seems to be a red herring. I just notice that startcheck.dat is the file that gets created and deleted now and that is the file I should be checking for when my Rpi boots. you beat me to it before I could answer my own question!

[bdbcat]

jimseng...


I stand corrected.
Thanks
Dave