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lunch - Online in the Cloud

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lunch - Distributed process launcher


lunch [config file] [options]


Lunch is a distributed process launcher for GNU/Linux. The Lunch master launches
lunch-slave processes through an encrypted SSH session if on a remote host. Those slave
processes can in turn launch the desired commands on-demand.


show program's version number and exit

-h, --help
show this help message and exit

-f CONFIG_FILE, --config-file=CONFIG_FILE
Specifies the python config file. You can also simply specify the config file as
the first argument.

Specifies the logging and pidfile directory for the master. Default is

-q, --log-to-file
Enables logging master infos to file and disables logging to standard output.

-g, --graphical
Enables the graphical user interface.

-v, --verbose
Makes the logging output verbose.

-d, --debug
Makes the logging output very verbose.

-k, --kill
Kills another lunch master that uses the same config file and logging directory.
Exits once it's done.


The lunch executable is called the lunch master. The lunch-slave executable is called the
lunch slave. If run as a master, it launches slaves. The slaves are responsible for
launching child processes. The master launches slaves (via SSH or not) which, in turn,
launch child processes.

The Lunch configuration file can be provided as a first argument to the lunch executable.
If not given, the Lunch master will look for the ~/.lunchrc file. If not found, lunch will
print an error and exit. The lunch config file is written in the Python programming
language, and must call the add_command function.

The process ID of the master is written to a file located in /var/tmp/lunch/master*.pid,
where * varies depending on the lunch config file used to configure the master. Here is
how to kill every lunch master on your system :

for f in /var/tmp/lunch/master-*.pid; do kill -15 $(cat $f); done


When invoked with the --graphical option, (-g) the lunch master shows a graphical user
interface displaying the state of every managed process. When this window is closed, the
lunch master exits and kills all its children processes.


If using for more than one host, lunch needs a SSH server installed on each remote
computer. It is also needed that the public SSH key of your user on the master computer
must be installed on every slave computer. Here is a summary of the steps to do to create
a SSH key on your master computer, and send your public key on each slave computer.

$ mkdir -p ~/.ssh
$ chmod 700 ~/.ssh
$ ssh-keygen -f ~/.ssh/id_rsa -t rsa

Next, for each slave host, do:

$ ssh-copy-id <username>@<host>
$ ssh username@host 'echo Hello'

The latter command should display "Hello" when issued.

If you start lunch via SSH, and launch from there commands other hosts, you must first
make sure that the ssh-agent is running and that you have unlocked your private SSH key.
It can be done like this:

$ ssh-agent bash
$ ssh-add


2010 - Ported from multiprocessing to Twisted

2009 - Written by Alexandre Quessy <[email protected]> with contributions from Simon
Piette <[email protected]>


See the examples directory for examples. On a Debian or Ubuntu system, they should located
in the /usr/share/doc/lunch/examples/ directory.

Here is the simplest example possible for the contents of a ~/.lunchrc file. It tells
Lunch to call only one command, called "xeyes".


If you add more calls to add_command in this file, it will add more processes to be
launched by Lunch. The add_command is the Python function you need to call from your Lunch
configuration file in order to add commands to be called by Lunch. If you add more than
one command, they will be called in the order you add them in the file.

Here is a more complex example of a configuration file. It creates three processes, with
dependencies between processes.

add_command("xeyes", identifier="xeyes")
add_command("xlogo", depends=["xeyes"])
add_command("xclock", depends=["xeyes", "xlogo"])

The configuration file above will first start xeyes, and next xlogo, and finally xclock.
If xeyes quits, all three processes will be stopped and restarted. If the xlogo process
quits, the xclock will be stopped and restarted again when the xlogo is running. The
"depends" keyword argument of the "add_command" function needs a list of strings as
argument. Those string must match the "identifier" keyword argument of an already added

In the next example, we use SSH to launch processes on a remote host. Note that the lunch-
slave script must be installed on each of the hosts on which to launch child processes.

add_command("xeyes", user="johndoe", host="example.org")

It will create a process tree such as this one :


The next one is a command that is run only once.

add_command("ls -l", identifier="listing...", respawn=False)

If, for some reason, it is easier for you to specify the host name for every command you
add, even for the local host, you can call "add_local_address" with the master's IP as an

# We will not use SSH for this one,
# since we just added its host using the
# "add_local_address" function.
user="johndoe", host="")
# We will use SSH for the next one,
# since its host is not set as being the local host.
add_command("xeyes -geometry 300x400",
user="johndoe", host="example.org")


See http://svn.sat.qc.ca/trac/lunch for help and documentation.

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