Re: [DNG] [OT] files disappearing reproducibly

2022-02-21 Thread Didier Kryn 

Le 21/02/2022 à 01:36, Steve Litt a écrit :

Florian Zieboll via Dng said on Sat, 19 Feb 2022 18:51:54 +0100



Back to the keyboard, I just discovered, that every (GUI) program I
run, is spawned from PID 1.

This is not precisely true. Even though ps ax lists the PPID of the
programs you run is 1, PID1 didn't spawn them. Here's the explanation...

When there's a desire to background a program in such a way that you
can close the parent program without closing the "spawned" program,
without using the problematic nohup, the iconic way to do it is called
"doublefork", which *assigns* the PPID to PID1.

As a doublefork example, the following is the C code my qownbackup
system uses to background the `qownbackup backup` command:

==
#include
#include

int main(int argc, char *argv[]){
 pid_t pid = fork();
 if(pid < 0){
 printf("First fork failed.\n");
 perror("First fork failed!");
 } else if(pid == 0){
 pid = fork();
 if(pid < 0){
 printf("Second fork failed.\n");
perror("Second fork failed!");
 } else if(pid == 0){
 execl("./qownbackup.sh", "./qownbackup.sh", "backup", NULL);
 }
 }
}
==

Aitor can correct any misunderstandings I have, but here goes my
explanation...

First, understand that the fork() function produces a second process,
called "the child", almost completely identical to the first. The
child's program counter is the same as the parent's, so both process
proceed from the point immediately after the fork() function.

The fork() function returns one of three ranges of integers:

* Less than 1 on error.
* Zero if the current process is the child.
* Greater than zero, and in fact the child's PID, if the process is
   the parent.

The child of a child is assigned a PPID of 1.

So the first thing is to do one fork, test the return code for error,
and abort if so. If the return code is positive, indicating that this
is the parent, do nothing, so that the parent finishes normally.

But if the return code is zero, this is the first child, so do another
fork. Once again, run the fork() function, and if the return indicate's
that you're a child (of the child the child the original created), do
an exec function to replace yourself with the command you want to
background, in this case "qownbackup backup".

Because it's the child of a child, its PPID is 1. Aitor, I don't think
I've given the complete story, I think there's a dependency on which
process finishes first, and as such I might have a race condition in my
code.

Also, I think I should have done a setsid() after the second fork, and
I should have done something to close stdin, and redirect stdout and
stderr, to a log file or to /dev/null.

The following is the (Python3) doublefork used in my UMENU2 software:

==
#!/usr/bin/python

import sys
import os

if os.fork():
 sys.exit(0)
if os.fork():
 sys.exit(0)
os.setsid()  ### New to 1.9.3, guarantees complete fork
sys.argv.pop(0)
executable = sys.argv[0]
os.execvp(executable, sys.argv)
==

In the preceding, errors aren't handled, so it just does two straight
forks and proceeds only if both return zero. Then it does a setsid(),
which I think my C implementation should have done too, and then exec's
the desired command, just like my C implementation does.

Doubleforking works in pretty much any computer language with the
fork(). You can even do it in bash or dash, but it's not so
straightforward.

SteveT


    Note that this double-fork has not to be implemented in processes 
launched from sysv-rc scripts, since the launching script already 
performs one of the forks and then dies. In a daemon you launch by hand, 
the critical thing is to detach from the controlling terminal (closing 
stdin is not enough), and start a new session (setsid). Then you don't 
care who is the parent of the daemon; when the parent dies, the daemon 
becomes a child of init, but who cares?


--     Didier

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Re: [DNG] Another reason for why I use Devuan

2022-02-21 Thread Arnt Karlsen 
On Fri, 18 Feb 2022 02:44:12 -0300, Gastón wrote in message 
<20220218054412.ga5...@devuan.devuan.com.ar>:

> On Thu, Feb 17, 2022 at 10:52:43PM -0500, Hendrik Boom wrote:
> > On Thu, Feb 17, 2022 at 05:41:59PM -0800, Syeed Ali wrote:  
> > > On Thu, 17 Feb 2022 15:25:05 -1000
> > > Joel Roth via Dng  wrote:
> > >   
> > > > On Thu, Feb 17, 2022 at 05:55:49PM -0700, Keith Christian via
> > > > Dng wrote:  
> > > > > This describes the machine ID:
> > > > > 
> > > > > https://www.freedesktop.org/software/systemd/man/machine-id.html
> > > > >  
> > > > 
> > > > So a creation of the freedesktop folks.   
> > > 
> > > 
> > > I like this quote:
> > >   
> > > > It should be considered "confidential", and must not be exposed
> > > > in untrusted environments,
> > > > ...  
> > 
> > Just checked.  On my pure devuan system,
> > there is no /etc/machine-id filre,
> > but there is a /var/lib/dbus/machine-id
> > 
> > Should I worry?  

..dunno, chk
https://www.mail-archive.com/dng@lists.dyne.org/msg24726.html

> I leave here the link to the thread with the discussion about
> machine-id that occurred in this list in 2019
> 
> https://www.mail-archive.com/dng@lists.dyne.org/msg24687.html
> 
> In /etc/default/dbus you can set the IDTYPE to be a RANDOM value.

..thanks for the remainder, I had a feeling I had forgotten something
of importance updating a wee spare ascii disk install to chimaera.

..lost a coupla days worth of emails and command line history in my 1GB 
stopped dead disk, after getting distracted from backup-ing blue smoking
the red and blue wiring off my other Precision M4400, crisy clear green
monochrome at 1920x1200@60Hz didn't leave enough video memory for any X 
on any plug-in screen, all the while while the consoles were annoyingly
consoling. ;oD

-- 
..med vennlig hilsen = with Kind Regards from Arnt Karlsen
...with a number of polar bear hunters in his ancestry...
  Scenarios always come in sets of three: 
  best case, worst case, and just in case.
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Re: [DNG] Another reason for why I use Devuan

2022-02-21 Thread Dr. Nikolaus Klepp via Dng 
Anno domini 2022 Mon, 21 Feb 18:08:20 +
 Arnt Karlsen scripsit:
> On Fri, 18 Feb 2022 02:44:12 -0300, Gastón wrote in message 
> <20220218054412.ga5...@devuan.devuan.com.ar>:
> 
> > On Thu, Feb 17, 2022 at 10:52:43PM -0500, Hendrik Boom wrote:
> > > On Thu, Feb 17, 2022 at 05:41:59PM -0800, Syeed Ali wrote:  
> > > > On Thu, 17 Feb 2022 15:25:05 -1000
> > > > Joel Roth via Dng  wrote:
> > > >   
> > > > > On Thu, Feb 17, 2022 at 05:55:49PM -0700, Keith Christian via
> > > > > Dng wrote:  
> > > > > > This describes the machine ID:
> > > > > > 
> > > > > > https://www.freedesktop.org/software/systemd/man/machine-id.html
> > > > > >  
> > > > > 
> > > > > So a creation of the freedesktop folks.   
> > > > 
> > > > 
> > > > I like this quote:
> > > >   
> > > > > It should be considered "confidential", and must not be exposed
> > > > > in untrusted environments,
> > > > > ...  
> > > 
> > > Just checked.  On my pure devuan system,
> > > there is no /etc/machine-id filre,
> > > but there is a /var/lib/dbus/machine-id
> > > 
> > > Should I worry?  
> 
> ..dunno, chk
> https://www.mail-archive.com/dng@lists.dyne.org/msg24726.html
> 
> > I leave here the link to the thread with the discussion about
> > machine-id that occurred in this list in 2019
> > 
> > https://www.mail-archive.com/dng@lists.dyne.org/msg24687.html
> > 
> > In /etc/default/dbus you can set the IDTYPE to be a RANDOM value.
> 
> ..thanks for the remainder, I had a feeling I had forgotten something
> of importance updating a wee spare ascii disk install to chimaera.

IMO it's set to RANDOM by default, at leaset it is on my machines. But I run 
daedalus.

Nik

> 
> ..lost a coupla days worth of emails and command line history in my 1GB 
> stopped dead disk, after getting distracted from backup-ing blue smoking
> the red and blue wiring off my other Precision M4400, crisy clear green
> monochrome at 1920x1200@60Hz didn't leave enough video memory for any X 
> on any plug-in screen, all the while while the consoles were annoyingly
> consoling. ;oD
> 



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Re: [DNG] lvm2 depends on systemd

2022-02-21 Thread aitor 

Hi Boian,

On 20/2/22 3:03, Boian Bonev wrote:


Hi,
Add --disable-notify-dbus - in my case
  it looks like to be properly set by the autodetection and it worked.
BTW lvm version 2.03.15 and I got a successful sd free build...
With best regards,
b.


It doesn't build successfully without disabling lvmlockd. I attach the log file:

https://www.gnuinos.org/files/lvm2_2.03.11-2.1_amd64.build  


and the config flags in debian/rules:

https://www.gnuinos.org/files/rules  

Cheers,

Aitor.


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Re: [DNG] lvm2 depends on systemd

2022-02-21 Thread aitor 



It doesn't build successfully without disabling lvmlockd.

I rectify: without modifying the quilt patch applied by debian.

llvm2-lockd is present in my packaging.

Aitor.



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