In solutions to a question on the book "Operating Systems Concepts" it indicates that issuing a trap not a privileged task. Why is that so?
Some instructions need special privileges to run at all, which most of the time means only the OS gets to execute them.
Most user processes (programs) will need to issue a trap / exception to get the OS to run these instructions.
If it were a privileged operation, it wouldn't be possible for a process to issue a system call.
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I have a process in windows which i am running in startup. Now i need to make it if somehow that process get killed or stopped i need to restart it again in Windows 10?
Is there any way. Process is a HTTP server which if somehow stopped in windows i need to restart it. I have tried of writing a power-shell in which I'll check task-list status of process and then if not found I'll restart but that is not a good way. Please suggest some good way to do it.
I have a golang exe; under a particular scenario my process got killed or stopped i need to start it up again automatically. This has to be done imediately after the exe got killed. What is the best way to achieve this?
I will give you a brief rundown. You can enable Audit Process Termination in local group policy of the machine as shown below. In your case, success audits would be enough. Please note that the pic is for Windows 7. It may change with OS.
Now every time a process gets terminated, a success event will be generated and written to the security eventlog.
This will allow you to create a task scheduler that triggers on the generation of this event that calls a script that would run the process again. Simple right?
Well, you might have some trouble setting that task up especially when you want to pass details about the generating event to the script. This should help you get through that.
You can user Task scheduler for this purpose. There is a option of "restart on failure" which can be selected and whenever your process get failed it will restart again.
Reference :- https://social.technet.microsoft.com/Forums/windowsserver/en-US/4545361c-cc1f-4505-a0a1-c2dcc094109a/restarting-scheduled-task-that-has-failed?forum=winserverManagement
If I run the following command in my session...
(Get-Process -Id $pid).CloseMainWindow()
I am able to gracefully shut down a process (no modal windows or other popups arise).
If, however, the pid is in another user's session on the same machine (running RDS), the process does not close, and CloseMainWindow() returns FALSE (it returns TRUE if it's running in my own session). It also works if I run the powershell from the other user's session.
I specifically need a way to gracefully shut down the program as the program has a few important cleanup actions required to keep its database in order. So stop-process or process.kill() will not work.
After lengthy research, it does not seem possible to do this. There is, however, a solution which met at least some of my requirements.
You can create a Windows Scheduled Task which is triggered on session disconnect. This allows you to run a cleanup job as the user, rather than as the administrator, which allows programs to exit gracefully.
It has two major drawbacks....
It is called even if the user just has a minor network interruption (so you have to build a wait() function in the script to sleep for a bit and then check if it is still disconnected - not a clean solution.
It isn't called during a log-off event. For that you need to use a logoff script triggered by GPO.
Hope this helps someone in the future.
The problem statement in short: Is there a way in LSF to pass a signal SIGCONT/SIGTSTP to all processes running within a job?
I have a Perl wrapper script that runs on LSF (Version 9.1.2) and starts a tool (Source not available) on the same LSF machine as the Perl script.
The tool starts 2 processes, one for license management and another for doing the actual work. It also supports an option where sending SIGSTSP/SIGCONT to both processes will release/reacquire the license (which is what I wish to achieve).
Running bkill -s SIGCONT <JOB_ID> only resumes the tool process and not the license process, which is a problem.
I tried to see if I can send the signals to the Perl script's own PGID, but the license process starts its own process group.
Any suggestions to move forward through Perl or LSF options are welcome.
Thanks,
Abhishek
I tried to see if I can send the signals to the Perl script's own PGID, but the license process starts its own process group.
This is likely your problem right here. LSF keeps track of "processes running within the job" by process group. If your job spawns a process that runs within its own process group (say by daemonizing itself) then it essentially is a runaway process out of LSF's control -- it becomes your job's responsibility to manage it.
For reference, see the section on "Detached processes" here.
As for options:
I think the cgroups tracking functionality helps in a lot of these cases, you can ask your admin if LSF_PROCESS_TRACKING and LSF_LINUX_CGROUP_ACCT are set in lsf.conf. If they aren't, then you can ask him to set them and see if that helps for your case (you need to make sure the host you're running on supports cgroups). In 9.1.2 this feature is turned on at installation time, so this option might not actually help you for various reasons (your hosts don't have cgroups enabled for example).
Manage the license process yourself. If you can find out the PID/PGID of the license process from within your perl script, you can install custom signal handlers for SIGCONT/SIGSTP in your script using sigtrap or the like and forward them to the license process yourself when your script receives them through bkill. See here.
Question 1) How do i shutdown my computer? is there any interrupt for this?
Question 2) I heard that acpi power options can be used to shutdown or restart or put the computer to sleep. mode. Well how to do it? are they in form of some routines that can be called? if so how to call them? or are they include in any of the interrupts?
Question 3) suppose when the os is running i press power button which is on the cabinet. then is any irq fired so that my os can prepare and shutdown the computer?
Edit:
Here i am talking about my Own OS not windows.
Here's a very informative blog post by Matthew Garrett describing how Windows and Linux implement rebooting; I assume shutdown is somewhat similar. In principle, there are many ways which should work. In practice, the problem is that BIOS'es and ACPI implementations are usually crappy and tested only with Windows, so the best way is probably to do as Windows does. Which, per the article I linked, is what Linux also does nowadays.
Answer 1. There are many ways to shutdown your computer.
Use shutdown option shown in Windows dialogue
Use shutdown command in command prompt
Use Task Manager to shutdown your computer
Press power button on cabinet to shutdown your computer.
I have an SNMP client, sending my PC SNMP traps with destination port 162.
I run a sniffer (Wireshark) from my PC, and see that the traps are indeed received.
The SNMP.exe and SNMPTRAP.exe system processes are up and running (I've even restarted them),and SNMPTRAP.exe is listening to port 162. I have no activated firewall (whether Windows or 3rd party).
The problem: On my PC I have three different applications, all registered to SNMPTRAP.exe. These are all off-the-shelf sw, not something I wrote. MG-SOFT Trap Ringer is, f.e., one of
them. NONE OF THEM CATCHES ANY OF THE TRAPS, and I have no idea where exactly the failure is.
Do you have any idea what may be causing this? Or how, perhaps, I can debug the SNMPTRAP.exe process?
Thanks!
You may disable Microsoft Trap Service in Services panel. Then MG-SOFT TRAP Ringer will work.
The reason is simply that when Microsoft's SnmpTrap.exe monitors port 162, it prevents other applications, such as MG-SOFT's one from monitoring that port.
How you can eliminate and corner the problem is, try below stuff.
How are sure its not catching traps ( since u see them in wireshark). I mean, should they be displayed on some GUI Screen, if yes are the fields empty? or logged into some file, if yes are you sure you are checking the correct file, have you configured either through conf files or command line options which file the traps need to be logged in?
If step 1 does not work, try installing or configuring the whole setup on different pc /laptop and see if it works?
If step 2 does not work, try a different trap daemon program ( SNMPTRAP.EXE), plenty of open source programs exist, if you could capture with different daemon program, then some issue with SNMPTRAP.EXE you are using.
I'm sure one of these steps should work for you, if not get back :)