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

DTACH is the way to go. It's a software you need to install like a lite version of screen. This is a better version of the "dtach"-method found above, it will install dtach if necessary. It's to be found here where you can also learn how to get the output of the process which is running in the background:

from fabric.api import run
from fabric.api import sudo
from fabric.contrib.files import exists


def run_bg(cmd, before=None, sockname="dtach", use_sudo=False):
    """Run a command in the background using dtach

    :param cmd: The command to run
    :param output_file: The file to send all of the output to.
    :param before: The command to run before the dtach. E.g. exporting
                   environment variable
    :param sockname: The socket name to use for the temp file
    :param use_sudo: Whether or not to use sudo
    """
    if not exists("/usr/bin/dtach"):
        sudo("apt-get install dtach")
    if before:
        cmd = "{}; dtach -n `mktemp -u /tmp/{}.XXXX` {}".format(
            before, sockname, cmd)
    else:
        cmd = "dtach -n `mktemp -u /tmp/{}.XXXX` {}".format(sockname, cmd)
    if use_sudo:
        return sudo(cmd)
    else:
        return run(cmd)

May this help you, like it helped me to run omxplayer via fabric on a remote rasberry pi!

Answer 2

This worked for me:

sudo('python %s/manage.py celerycam --detach --pidfile=celerycam.pid' % siteDir)

Edit: I had to make sure the pid file was removed first so this was the full code:

# Create new celerycam
sudo('rm celerycam.pid', warn_only=True)
sudo('python %s/manage.py celerycam --detach --pidfile=celerycam.pid' % siteDir)

Answer 3

nohup did not work for me and I did not have tmux or dtach installed on all the boxes I wanted to use this on so I ended up using screen like so:

run("screen -d -m bash -c '{}'".format(command), pty=False)

This tells screen to start a bash shell in a detached terminal that runs your command

Answer 4

you just need to run

run("(nohup yourcommand >& /dev/null < /dev/null &) && sleep 1")