We have a rack mounted PC that is running LynxOS. It doesn’t have any GUI and it just controls our chassis dynamometer. Two weeks ago the system had (unrelated to my current problem) issues and I had to reboot it several times. After one reboot it just ceased booting up. The OS loading gets stuck after the “preboot” has been run. It just shows the LynxOS version number and becomes passive. Typing can bee seen on the screen but it doesn’t respond to anything.
Our Linux specialist tried to check the old HDD but couldn’t easily access it. I have since learned that Lynx OS uses a filesystem type that has compatibility issues with other systems. We just decided that the HDD had failed.
I purchased a new preconfigured HDD from the dynamometer manufacturer. Today I installed and everything was fine again. The next step to take a backup image of the HDD.
But an UPS unit inside the device had issues so had problems getting the system to power off. I tried to manual shutdown the LynxOS machine but couldn’t remember what option should I use to shut it down. My mind was stuck in DOS/Windows world and I typed “reboot /?” to see help for the command. The system immediately rebooted and to my surprise it got stuck in the same loading screen as it did with the “failed HDD”.
Then I begun thinking. When the original getting stuck issue appeared I had tried to reboot it using “reboot -a” command.(which is a common procedure when the system has issues).
But at this point I had the keyboard mounted directly to the LynxOS machine. Usually I have been sorting out the problems using a terminal and a serial connection. The keyboard that I was using has a Nordic layout but the machine expects to see an English layout. Among the differences between these keyboards is that symbol “-” in the keyboard will give “/” to the recipient. So instead of “reboot -a” I might have accidentally given a command “reboot /a”.
So it’s possible that “reboot /a” and “reboot /?” can make the HDD unbootable. We have another dynamometer using LynxOS too. I did check the man information for the “reboot” command. There are only “-a” and other similar options listed but nothing about using “/”.
While Googling I did learn that with some Linux/Unix OSes “reboot /something” is related to “runlevel” modes. I couldn’t still understand what my accidentally given commands would actually do. And I’m not going to test this with the still operating machine. The best guess that I have is that they force the system to go to “0" or “halt” mode during the boot. This sounds like a fairly silly explanation and it did require two typing coincidences.
I can give some commands during the “preboot”. But nothing that would let me see the actual filesystem. The boot command is given as “b ide.0a /lynx.os”. The other machine hinted that there could be also “/lynx.os_recovery” but using it instead doesn’t change anything about getting stuck. The command is accepted however. The preboot gives an error if I put some random extra letters (for example “/lynx.os_recoveryy”) and try to boot something that clearly doesn’t exist. So the filesystem seems to be still somewhat intact.
I’m really bugged about this issue now. Does anyone have ideas what could happen to an Unix related machine with “reboot /something” command?
Update: I managed to find a solution for the problem. My guess about the “halt” state was somewhat correct but I cannot offer answers to how or why questions.
In the preboot the “b” boot command has options (around 10 letters). These are listed but their functionality is annoyingly undocumented. I did find a 19 yesr old Google group discussion about booting up a LynxOS system straight to the “multi-user-mode”.
This could be done by adding -a to the boot command (similarly that I did while rebooting). So “b -a ide.0a /lynx.os” did revive the machine.