Really detaching jobs

Really detaching jobs

[Dominik Vogt]

Assuming a client machine is running a terminal emulator which is
running an ssh connection to the server and zsh through that
connection:

  Client: rxvt -> ssh
  Server: sshd -> zsh ->some job

  $ cd gcc-sources/build
  $ make -k check-gcc

Is there a way to *really* detach the job so that it will complete
if I close the terminal emulator or kill the ssh connection?

  <ctrl-z>
  bg
  disown %

doesn't work and neither does

  make check-gcc &!

I could use nohup, but then I need to plan that before issuing the
command.  The cases I care about are really jobs like a test run
of Gcc which can take make hours and cannot be simply continued
after interruption.

Ciao

Dominik ^_^  ^_^

Re: Really detaching jobs

[Jun T.]

2015/10/02 20:56, Dominik Vogt <vogt@linux.vnet.ibm.com> wrote:

> Is there a way to *really* detach the job so that it will complete
> if I close the terminal emulator or kill the ssh connection?

You may try GNU screen: https://www.gnu.org/software/screen/
It has a "detach" command, which is exactly what you want.

Searching the net for "GNU screen" will find lots of introductions
and tutorials.

Re: Really detaching jobs

[Dominik Vogt]

On Fri, Oct 02, 2015 at 09:43:58PM +0900, Jun T. wrote:
> 
> 2015/10/02 20:56, Dominik Vogt <vogt@linux.vnet.ibm.com> wrote:
> 
> > Is there a way to *really* detach the job so that it will complete
> > if I close the terminal emulator or kill the ssh connection?
> 
> You may try GNU screen: https://www.gnu.org/software/screen/
> It has a "detach" command, which is exactly what you want.

Yeah, but if I had known *in advance* that I'd have the problem,
I'd just have used nohup.  So the question is really how to detach
a running process group from the controlling terminal, and whether
zsh can help with that in any way (which I guess it cannot).

Ciao

Dominik ^_^  ^_^

-- 

Dominik Vogt
IBM Germany

Re: Really detaching jobs

[Bart Schaefer]

On Fri, Oct 2, 2015 at 7:38 AM, Dominik Vogt <vogt@linux.vnet.ibm.com> wrote:
>
>
> Yeah, but if I had known *in advance* that I'd have the problem,
> I'd just have used nohup.  So the question is really how to detach
> a running process group from the controlling terminal, and whether
> zsh can help with that in any way (which I guess it cannot).
>

Chances are that the reason the process dies is because sshd has
closed the standard output (the terminal) so it gets a write error.
The only reliable way to detach something is to redirect its outputs
(and inputs), which nohup does.  Once the process is running, there's
(generally) no external way to change those file descriptors, the
shell can't do anything after the fact.

The advantage of something like "screen" is that if you ALWAYS use it,
you can stop worrying about knowing in advance.

Re: Really detaching jobs

[covici]

Dominik Vogt <vogt@linux.vnet.ibm.com> wrote:

> On Fri, Oct 02, 2015 at 09:43:58PM +0900, Jun T. wrote:
> > 
> > 2015/10/02 20:56, Dominik Vogt <vogt@linux.vnet.ibm.com> wrote:
> > 
> > > Is there a way to *really* detach the job so that it will complete
> > > if I close the terminal emulator or kill the ssh connection?
> > 
> > You may try GNU screen: https://www.gnu.org/software/screen/
> > It has a "detach" command, which is exactly what you want.
> 
> Yeah, but if I had known *in advance* that I'd have the problem,
> I'd just have used nohup.  So the question is really how to detach
> a running process group from the controlling terminal, and whether
> zsh can help with that in any way (which I guess it cannot).
> 

I just always use tmux and zsh and so if there is a disconnect, its good
to go.  Tmusx is just a better version of screen.

-- 
Your life is like a penny.  You're going to lose it.  The question is:
How do
you spend it?

         John Covici
         covici@ccs.covici.com

Re: Really detaching jobs

[Mikael Magnusson]

On Fri, Oct 2, 2015 at 4:38 PM, Dominik Vogt <vogt@linux.vnet.ibm.com> wrote:
> On Fri, Oct 02, 2015 at 09:43:58PM +0900, Jun T. wrote:
>>
>> 2015/10/02 20:56, Dominik Vogt <vogt@linux.vnet.ibm.com> wrote:
>>
>> > Is there a way to *really* detach the job so that it will complete
>> > if I close the terminal emulator or kill the ssh connection?
>>
>> You may try GNU screen: https://www.gnu.org/software/screen/
>> It has a "detach" command, which is exactly what you want.
>
> Yeah, but if I had known *in advance* that I'd have the problem,
> I'd just have used nohup.  So the question is really how to detach
> a running process group from the controlling terminal, and whether
> zsh can help with that in any way (which I guess it cannot).

This may work with varying degrees of success, https://github.com/nelhage/reptyr

-- 
Mikael Magnusson

Re: Really detaching jobs

[Dominik Vogt]

On Fri, Oct 02, 2015 at 08:45:21PM +0200, Mikael Magnusson wrote:
> On Fri, Oct 2, 2015 at 4:38 PM, Dominik Vogt <vogt@linux.vnet.ibm.com> wrote:
> > 2015/10/02 20:56, Dominik Vogt <vogt@linux.vnet.ibm.com> wrote:
> > Is there a way to *really* detach the job so that it will complete
> > if I close the terminal emulator or kill the ssh connection?
> 
> This may work with varying degrees of success, https://github.com/nelhage/reptyr

That's what I was looking for.

  $ reptyr PID > /dev/null 2>&1

does the trick.  Thanks!

Ciao

Dominik ^_^  ^_^

-- 

Dominik Vogt
IBM Germany