[9fans] Backgrounding a task

[giacomo@tesio.it (Giacomo Tesio)]

Here it is: https://github.com/JehanneOS/jehanne/commit/320e6e6f35bfbc2e37dbd079c8d6a9124bd9ac6c

The simple test attached confirms that it works as expected:
https://github.com/JehanneOS/jehanne/blob/master/qa/kern/nsclone.c

Now it's just matter of modifying the plumber to use this facility and
add a ns/clone command that take a pid and a command to run so that

ns/clone 256 rc

would start a new rc in a copy of the name space of the process with pid 256.


Giacomo


2017-10-24 21:18 GMT+02:00 Giacomo Tesio <giacomo at tesio.it>:
> 2017-10-24 16:21 GMT+02:00 Alex Musolino <alex at musolino.id.au>:
>> Creating a child process is something that a process explicitly
>> controls and the RFNOTEG flag of rfork(2) allows a process to control
>> whether or not it shares its namespace with its children.  Allowing
>> other, unrelated processes to fiddle with your namespace is quite
>> different.
>>
>> Think about multiple processes owned by multiple users running on a
>> cpu server.  Which processes should be allowed to join which
>> namespaces?
>>
>> Perhaps allowing only the hostowner to join namespaces for debugging
>> and administration purposes would be acceptable.
>
> I like this idea a lot. I will give it a try in Jehanne.
>
> However I'm going to use a slightly different design: writing "clone"
> to /proc/$pid/ns will cause the current process to replace its own
> name space with a *copy* of that of $pid.
> If the owner of $pid is different from that of the current process or
> if $pid is not running on the same machine as the current process, the
> write will fail with an error.
>
> However any change to the name space after the clone does not impact
> the original process.
>
> As for the plumber, I will add a message that make the plumber clone
> the name space of a target process.
>
> This should address both use-cases without issues for the processes
> running in the original name space.
>
>
> Giacomo