start a background process with nohup using fabric

Question

am trying to start a celerycam process using fabric using the below nohup command. Unfortunately, nothing is happening, manually using the same command i could start the pro

Answer 1

I'm using Erich Heine's suggestion to use 'dtach' and it's working pretty well for me:

def runbg(cmd, sockname="dtach"):
    return run('dtach -n `mktemp -u /tmp/%s.XXXX` %s' % (sockname, cmd))

This was found here.

Answer 2

I was able to circumvent this issue by running nohup ... & over ssh in a separate local shell script. In fabfile.py:

@task
def startup():
    local('./do-stuff-in-background.sh {0}'.format(env.host))

and in do-stuff-in-background.sh:

#!/bin/sh

set -e
set -o nounset

HOST=$1

ssh $HOST -T << HERE
   nohup df -h 1>>~/df.log 2>>~/df.err &
HERE

Of course, you could also pass in the command and standard output / error log files as arguments to make this script more generally useful.

(In my case, I didn't have admin rights to install dtach, and neither screen -d -m nor pty=False / sleep 1 worked properly for me. YMMV, especially as I have no idea why this works...)

Answer 3

This is an instance of this issue. Background processes will be killed when the command ends. Unfortunately on CentOS 6 doesn't support pty-less sudo commands.

The final entry in the issue mentions using sudo('set -m; service servicename start'). This turns on Job Control and therefore background processes are put in their own process group. As a result they are not terminated when the command ends.

For even more information see this link.

Answer 4

You could be running into this issue

Try adding 'pty=False' to the sudo command (I assume virtualenv is calling sudo or run somewhere?)

Answer 5

As I have experimented, the solution is a combination of two factors:

• run process as a daemon: nohup ./command &> /dev/null &
• use pty=False for fabric run

So, your function should look like this:

def background_run(command):
    command = 'nohup %s &> /dev/null &' % command
    run(command, pty=False)

And you can launch it with:

execute(background_run, your_command)

Answer 6

You can use :

run('nohup /home/ubuntu/spider/bin/python3 /home/ubuntu/spider/Desktop/baidu_index/baidu_index.py > /home/ubuntu/spider/Desktop/baidu_index/baidu_index.py.log 2>&1 &', pty=False)