I had putty on one server and run a python script available on that server. That script keep on throwing output on terminal. Later on, my internet connection went off but even then i was expecting my script to complete it job as script is on running on that server. But when internet connection resumed, I found that script has not done its job.
So is this expected ? If yes, then what to do to make sure that script runs on server even though internet connection goes off in-between?
Thanks in advance !!!
You should use screen which will let you "detach" your process from the actual terminal you're in.
On the server, you can install tmux or screen. These programs run the program in the background and enable you to open a 'window', If I use tmux:
Open tmux: tmux
Detach (run in background): press Ctrl-b d
reattach (open a 'window'): tmux attach
Related
What is the correct way to have python schedule (by daniel bader) persistently run. I currently run the job by having a terminal open, connected to a VM where the scripts actually run. There I run python "scheduler.py" - where scheduler.py has all the jobs.
But when the connection closes, or I close the terminal, the scheduler stops.
Any easy solutions to fix this?
You have a couple options here. You are starting the process in your ssh session, but then killing the ssh session, which then kills the process.
One way to handle this, would be to have the VM run the script on startup. You could set the script as a service, so even if it goes down for some reason it will come back up. Read into init.rc for info on how launch a script at boot on linux. I'm not well-versed in Windows any more but I believe there is a way to do the same.
Another option is to keep the session open by connecting to it with screen or tmux. This article explains the problem some and gives you a few different ways to work around the issue: https://www.tecmint.com/keep-remote-ssh-sessions-running-after-disconnection/
I've created a script for my school project that works with data. I'm quite new to working remotely on a server, so this might seem like a dumb question, but how do I execute my script named
stats.py
so that it continues executing even after I log off PuTTy? The script file is located on the server. It has to work with a lot of data, so I don't want to just try something and then few days later find out that it has exited right after I logged off.
Thank you for any help!
There are many ways you can run a python program after you disconnect from an SSH session.
1) Tmux or Screen
Tmux is a "terminal multiplexer" which enables a number of terminals to be accessed by a single one.
You start by sshing as you do, run it by typing tmux and executing it. Once you are done you can disconnect from putty and when you login back you can relog to the tmux session you left
Screen also does that you just type screen instead of tmux
2) nohup
"nohup is a POSIX command to ignore the HUP signal. The HUP signal is, by convention, the way a terminal warns dependent processes of logout."
You can run it by typing nohup <pythonprogram> &
I have written some Web services in Python.I want to deploy it in AWS, I have created the instance.
I tried to run using putty and it was coming up well using the command python Flo.py, which starts the server 0.0.0.0:8080. But the problem is when I close the putty window the server is terminating. How i can start a server in 8080 just like httpd?
All helps are invited
I highly recommend you use screen (or tmux). And you may want to use upstart as well.
Screen:
Screen is a full-screen window manager that multiplexes a physical terminal between several processes (typically interactive shells).
tmux and screen are doing the same thing - which is terminal multiplexing. This will give you a terminal you can attach to and disconnect from to keep it running when you're not on the server.
To test it simply install using:
sudo apt-get install screen
Now use the following to open a screen terminal under the name my_screen, running your script as it starts:
screen -dmS my_screen python Flo.py
And attach to it using:
screen -r my_screen
Detach using ctrl+A followed by ctrl+D, and now you can leave the server (screen will keep running with the process in it)
Read more here.
Upstart:
Upstart is an event-based replacement for the /sbin/init daemon which handles starting of tasks and services during boot, stopping them during shutdown and supervising them while the system is running.
Upstart is the new way to start services on debian as soon as the system starts.
To add an upstart service you need to add a configuration file under /etc/init (open one of the files there and see an example).
These files can be extremely simple so don't be intimidated by what you see there.
You can make a service to run your server / service and send output to a log file which you can then use to keep track of what's happening.
Read more here.
I have a python script that basically runs forever and checks a webpage every second and notifies me if any value changes. I placed it on an AWS EC2 instance and ran it through ssh. The script was running fine when I checked after half an hour or so after I started it.
The problem is that after a few hours when I checked again, the ssh had closed. When I logged back in, there was no program running. I checked all running processes and nothing was running.
Can anyone teach me how to make it run forever (or until I stop it) on AWS EC2 instances? Thanks a lot.
Edit: I used the Java SSH Client provided by AWS to run the script
You can use Linux screen.Linux screen tool can not only save you from disconnection disasters, but it also can increase your productivity by using multiple windows within one SSH session.
To install:
sudo apt-get install screen
Start a new session:
screen -S <screen_name>
Run your process as you run it in the screen session. If you want to back to your main terminal press key shortcut ctrl+a+d. And also view the screen by typing,
screen -r <screen_name>
You can run the program using the nohup command, so that even when the SSH session closes your program continues running.
Eg: nohup python yourscriptname.py &
For more info you can check the man page for it using
man nohup.
So I have tornado server setup on my vps running ubuntu 12.04. So when I am ssh'd into my server or am vnc'd in there the site loads static/templates files just fine. But when I exit out of ssh or terminate vnc python throws error that the file it was looking for does not exist.
[Errno 2] No such file or directory
When I execute the server I just run the python command to run it as a background process, and once its successfully running and exit out.
I have the server running at www.calapp.manangandhi.com
Edit: As per the answer below I was able to figure out a way for it to work. here si the link to daemonizing tornado application, there are other ways suggested in the thread as well. https://groups.google.com/forum/?fromgroups=#!topic/python-tornado/4cxKEFsS0RE
Are you trying to say that you run the server from within the ssh shell? If so, your problem is most likely that on shutdown of the shell, the software gets a HUP and disconnects despite being in the background. You need the software to daemonize and detach completely from the running terminal. If you're using a toolkit, look up "starting as daemon" or launch your software from within DJB's supervise or other system-wide launcher system.