I want to run following command in terminal: sudo service motion start.
If I do that by myself, it will work fine - the camera is going to stream on specific port. But, if I run it in Python with: os.system("sudo service motion start"), it will still start service at specific port but won't show stream of the camera - it will show gray picture with counting date and time.
Some other options such as subprocess.call() didn't work either.
I would like to run that particular command from Python. I don't mind if terminal window opens (and closes afterwards), but it would be the best case if it doesn't open and command simply runs somewhere in background.
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I am writing a Python CGI script that I want to run on my laptop's browser. This script will SSH into two Pis, and give the command to take a photo. The server hosting this script is on one of the Pis that I want to SSH into, and that Pi also is acting as an access point for the other Pi and my laptop to connect to (everything is a LAN, not connected to the Internet).
I am successfully able to run this script on my laptop's browser to run simple commands like ls -l on both Pis and print out the results for both on the browser. But, I ultimately want to be able to give the raspistill command to both Pis. When I do this, only the Pi with the server is taking the image, but the other Pi is not. I assume it's because permissions aren't set properly for the server (I tried running the commands as sudo but still no luck). However, if I run the same script on a Python IDLE it works fine. Can somebody help me identify the issue?
Here is my script:
#! /usr/bin/env python3
from pssh import ParallelSSHClient
import cgi
print("Content-Type: text/plain\r\n")
print("\r\n ")
host = ['172.24.1.1','172.24.1.112']
user = 'XXXX'
password = 'XXXX'
client = ParallelSSHClient(host, user, password)
output = client.run_command('raspistill -o test.jpg', sudo=True)
// AMENDMENT:
for line in output['172.24.1.1'].stdout: // works as well with '172.24.1.112'
print(line)
AMENDMENT:
Apparently, if I output anything from the stdout it works fine. Why is this the case? Is is just waiting for me flush the output or something? I suspect this might be a issue with the pssh package I am using.
In your pi, go into the terminal and type sudo raspi-config and then navigate with the keys to camera and then enable it. This will restart you pi.
From https://www.raspberrypi.org/documentation/configuration/camera.md:
Use the cursor keys to move to the camera option, and select 'enable'.
On exiting raspi-config, it will ask to reboot. The enable option
will ensure that on reboot the correct GPU firmware will be running
with the camera driver and tuning, and the GPU memory split is
sufficient to allow the camera to acquire enough memory to run
correctly.
After this, go into sudo raspi-config and enable ssh (which is another option just like pi-camera). Link for this here
After thoroughly reading through the documentation for the pssh module, my problem had to do with the exit codes and how they are handled.
The documentation about run_command states that:
function will return after connection and authentication establishment and after commands have been sent to successfully established SSH channels.
And as a result:
Because of this, exit codes will not be immediately available even for
commands that exit immediately.
Initially, I was just blindly running the run_command expecting the commands to finish, but it turns out I need to get the exit codes to truly finish the processes the commands are running. The documentations states a couple of ways to do this:
At least one of
Iterating over stdout/stderr to completion
Calling client.join(output) is necessary to cause parallel-ssh to wait for commands to finish and be able to gather exit codes.
This is why in my amendment to the code, where I was outputting from stdout, the commands seemed to work properly.
I have really tried looking around but all the examples I find do not work for me.
I have a python script in a Raspberry Pi that starts using CRON....all good!
I would like to be able to debug the ouput that the script prints in screen from time to time so the "screen" command needs to be used to create a session and ensure that I can login and logoff using putty as needed.
I also add the "&" so it will run in background.
So currently I did:
1) Open cron
sudo crontab -e
2) Add the following line
#reboot python /home/pi/python/monitor.py &
This works correctly, I just need to know how to make a "screen" session open before launching the python script.
Thank you very much for your help!
I have an external server that I can SSH into. It runs bots on reddit.
Whenever I close the terminal window the bot is running in, the process stops, which means the bot stops as well.
I've tried using
nohup python mybot.py
but it doesn't work - when I close the window and check the processes (ps -e), python does not show up. Are there any alternatives to nohup? Ideally, that print the output to the terminal, instead of an external file.
Have you considered using tmux/screen? They have lots of features and can help you detach a terminal and re-attach to it at a later date without disrupting the running process.
Here's a short description of what I have:
I have to raspberry pi's in a local net work. I one of them I have a .py script named watchdog.py that starts a stream and then uses a sshpass command to the other pi to display the video stream.It also has some signaling LEDs a some push buttons for control
the problem is:
If I open a terminal and run the watchdog.py script in the GUI everything runs as it should be. So I thought of running it as a service as boot and installed upstart and made it run as a service (successfully I think). The thing is. If I boot the pi and then press the button to start the streams,they wont play on the other Pi, the LEDs ligh up and all the buttons work. And even the CPU load behaves the same way, but i still don't video nor audio. I have thought of trying automatically open a terminal (LXterminal) widow and run the python scrip on that window. but I didn't want the streaming raspberry pi also booting into gui (tough I guess I would mind if that makes the whole thing work).This little thing i making the whole project useless.
What are you using to play the streams? Depending on how you boot up the second Raspberry it might not have started some daemons for audio/video playback?!
You should (if you're not already doing) write a log (import logging ;)) and write a logfile which you can track for errors.
answer moved from OP's question itself:
I found a way that seems to work so far. instead of running the python script as a service I tried running it as cron job at reboot, and it worked. now it all works straight from reboot and I have Audio and video.
I've setup an Amazon EC2 server. I have a Python script that is supposed to download large amounts of data from the web onto the server. I can run the script from the terminal through ssh, however very often I loose the ssh connection. When I loose the connection, the script stops.
Is there a method where I tell the script to run from terminal and when I disconnect, the script is still running on the server?
You have a few options.
You can add your script to cron to be run regularly.
You can run your script manually, and detach+background it using nohup.
You can run a tool such as GNU Screen, and detach your terminal and log out, only to continue where you left off later. I use this a lot.
For example:
Log in to your machine, run: screen.
Start your script and either just close your terminal or properly detach your session with: Ctrl+A, D, D.
Disconnect from your terminal.
Reconnect at some later time, and run screen -rD. You should see your stuff just as you left it.
You can also add your script to /etc/rc.d/ to be invoked on book and always be running.
You can also use nohup to make your script run in the background or when you have disconnected from your session:
nohup script.py &
The & at the end of the command explicitly tells nohup to run your script in the background.
If it just a utility you run ad-hoc, not a service daemon of some kind, i would just run it in screen. Than you can disconnect if you want and open the terminal back up later... Or reconnect the terminal if you get disconnected. It should be in your linux distros package manager. Just search for screen
http://www.gnu.org/software/screen/
nohup runs the given command with hangup signals ignored, so that the command can continue running in the background after you log out.
Syntax:
nohup Command [Arg]...
Example:
nohup example.py
nohup rasa run
Also, you can run scripts continuously using the cron command.
For more:
https://ss64.com/bash/nohup.html
https://opensource.com/article/17/11/how-use-cron-linux