This allow submanager to do some cleanup when it receive sigterm
(in this case removing pid file and killing subprocess).

This script allow to run a command and restart it
it if some files changes.

The submanager catch SIGUSR1 and checks if the specified
files has changed.

It can use a pid file where its own pid is written.

This is usefull for restarting a service from a recipe.

Example :
  submanager -c config.cfg -- command --with-options -y
    Run “command --with-options -y” and restart it if
    config.cfg is modified after receiving SIGUSR

in slapos.toolbox.

The server listen on an unix socket and wait for a json request which
look like :
  {"command": "/command/to/run",
   "timestamp": 0}

The server respond sending back the command it will run.

The server is single threaded on run each command only one by one.

If one command requested two times with the same time stamp, it
will be runned only once.

a simple script which download any http resource
and save it into a specified file_path

usage: onetimedownload URL FILE_PATH

When removing instance : chmoding directories that are not writable because some instances do 'chmod 555' on directories.