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Re: getting a regular user to dump core when a program crashes

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	Hi.

On Mon, Feb 28, 2022 at 11:41:27AM -0500, The Wanderer wrote:
> On 2022-02-28 at 11:35, Greg Wooledge wrote:
> 
> > On Mon, Feb 28, 2022 at 11:25:13AM -0500, songbird wrote:
> >
> >> >> me@ant(14)~$ ulimit -a
> >> >> real-time non-blocking time  (microseconds, -R) unlimited
> >> >> core file size              (blocks, -c) unlimited
> >> 
> >>   i had accomplished the ulimit change already, but the lack of 
> >> the proper permission on the output directory meant that a core
> >> file would not be generated.
> > 
> > What is an "output directory"?  Core files are dumped in the process's
> > *working* directory, which is "where you are when you run it".
> 
> By default, yes, that's the case. However, from songbird's original
> post:
> 
> >>>> i have the following set in my /etc/sysctl.conf:
> >>>> 
> >>>> # core file location and file name format
> >>>> kernel.core_pattern=/crash/core.%u.%E.%p
> 
> That appears to be a kernel parameter which defines the path and
> filename of the core file.

It can do that too. Quoting the relevant part of the kernel's
documentation (admin-guide/sysctl/kernel.rst.gz) :

If the first character of the pattern is a '|', the kernel will treat
the rest of the pattern as a command to run.  The core dump will be
written to the standard input of that program instead of to a file.


For instance, one can use systemd-coredump (needs a package installed,
though) to write backtraces to journald.
Or, one can specify /dev/null in kernel.core_pattern, thus preventing
core dumps from creating regardless of user's shell limits.


> and that the syntax of the kernel parameter in question is
> such that you have to specify the full path to the file.

When used in such way, it's also prevents user's processes to spam an
entire filesystem with coredumps.

Reco

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Thread

getting a regular user to dump core when a program crashes songbird <songbird@anthive.com> - 2022-02-28 16:10 +0100
  Re: getting a regular user to dump core when a program crashes Greg Wooledge <greg@wooledge.org> - 2022-02-28 16:40 +0100
    Re: getting a regular user to dump core when a program crashes songbird <songbird@anthive.com> - 2022-02-28 17:30 +0100
      Re: getting a regular user to dump core when a program crashes Greg Wooledge <greg@wooledge.org> - 2022-02-28 17:40 +0100
        Re: getting a regular user to dump core when a program crashes The Wanderer <wanderer@fastmail.fm> - 2022-02-28 17:50 +0100
          Re: getting a regular user to dump core when a program crashes songbird <songbird@anthive.com> - 2022-02-28 18:00 +0100
          Re: getting a regular user to dump core when a program crashes Reco <recoverym4n@enotuniq.net> - 2022-02-28 18:20 +0100
          Re: getting a regular user to dump core when a program crashes Greg Wooledge <greg@wooledge.org> - 2022-02-28 18:30 +0100
            Re: getting a regular user to dump core when a program crashes songbird <songbird@anthive.com> - 2022-02-28 19:50 +0100

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