[Bug 160999] Re: Apport doesn't overwrite existing core files

[Tjd]

@k04jg02, as noted in comment #7, this bug has no effect on the Ubuntu
Error Reporting process for software that is distributed through normal
channels.

Instead, for software that comes from any other source, apport seems to
make a 'best-efforts' approach to dump a core file, roughly following
some of the conventions of the usual core dump procedure. However,
there's nothing in core(5) that says that any downstream program
receiving a core dump (in this case apport) must do anything specific
with it.

That said, for developers, and in particular newbies trying to get into
coding, apport's behavior is fairly insidious and confusing. Here are a
few suggestions and possible workarounds for consideration:

-[partial workaround] If you set the `kernel.core_uses_pid` sysctl to 1,
apport respects this and always generates core.PID files. This doesn't
solve the broken default behavior, and also doesn't guarantee a new
file, since PIDs can be reused, but it helps. (`sysclt
kernel.core_uses_pid=1`, or edit /etc/sysctl.conf)

-[questionable workaround] Use apport to capture crashes for unpackaged software, by adding the lines 
```[main]
unpackaged=true```
to ~/.config/apport/settings. Now your program crashes will be handled like those of any Ubuntu-provided software: They will generate a .crash file in /var/crash (which can be unpacked with apport-unpack to access the core dump); they will generate an apport crash dialog box, and will even be uploaded to errors.ubuntu.com by whoopsie if you check the 'Send error report' box, (which is almost certainly a bad idea).

-[upstream solution] kernel could support both writing out a core file
(according the rules in core(5) , and passing the core to an external
program. This would be ideal, since it would not require apport to try
to duplicate and track kernel core dump behavior.

-[mitigation] Patch apport to just make the default behavior a little
more sane, even if not perfectly copying the usual behavior.

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https://bugs.launchpad.net/bugs/160999

Title:
  Apport doesn't overwrite existing core files

Status in apport package in Ubuntu:
  Triaged

Bug description:
  While debugging some code, I noticed that existing core files aren't
  being overwritten when they should be.  According to core(5), the
  following file should be overwritten, but it's not:

  bam:/tmp$ id -un
  gerald
  bam:/tmp$ ls -l core
  -rw------- 1 gerald gerald 3407872 2007-10-30 21:22 core
  bam:/tmp$ date
  Thu Nov  8 09:36:23 PST 2007
  bam:/tmp$ ./coretst 
  Segmentation fault (core dumped)
  bam:/tmp$ ls -l core
  -rw------- 1 gerald gerald 3407872 2007-10-30 21:22 core

  Creating the initial core file works fine:

  bam:/tmp$ rm core
  bam:/tmp$ ./coretst 
  Segmentation fault (core dumped)
  bam:/tmp$ ls -l core
  -rw------- 1 gerald gerald 163840 2007-11-08 09:36 core
  bam:/tmp$ date
  Thu Nov  8 09:36:49 PST 2007

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