Re: [HACKERS] Debian no longer dumps cores?

Hi,

My Debian system (now running Linux 2.6.26) is no longer dumping core
files, and I can't figure out why :-(

Of course, I've set ulimit -c to unlimited, and I'm running the
postmaster directly in the same shell (no pg_ctl or init scripts), but
it's still not working. I'm not sure where else to look; Google
searches return tons of junk but nothing useful.

The kernel was compiled by me to add oprofile support, though I used
Debian's .config to generate the base config, and changed nothing else
(no time to fiddle).

If anybody has any idea of what's going on I'd appreciate it.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

On Mon, 20 Oct 2008, Alvaro Herrera wrote:

> My Debian system (now running Linux 2.6.26) is no longer dumping core
> files, and I can't figure out why :-(

My guess is that you're being nailed by one of the changes related to
implementing the improved capabilities interface made in 2.6.25 or 2.6.26.
I know that broke some libpcap versions for example:
http://lkml.org/lkml/2008/4/22/18

I haven't upgraded a Debian system to a kernel that new yet myself to know
specifically what's wrong, the blog posting at
http://linux-man-pages.blogspot.com/2008/05/capabilities-have-fully-arrived-finally.html
is a good starter point to dig for more info. If I had to make a guess
I'd suspect whatever is dumping core doesn't have the CAP_SYS_RAWIO
capability needed to access /proc/kcore and you need to tweak a file
related to that area rather than the ulimit stuff.

Also worth mentioning is that you may need to adjust
/proc/sys/fs/suid_dumpable (see
http://manpages.courier-mta.org/htmlman5/proc.5.html ) and that there have
been distributions that just broke even the CAP_SYS_RAWIO interface at the
kernel level; see http://vir.homelinux.org/blog/archives/30-Lost-time.html
for an example.

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Mon, Oct 20, 2008 at 05:49:04PM -0300, Alvaro Herrera wrote:
> Hi,
>
> My Debian system (now running Linux 2.6.26) is no longer dumping core
> files, and I can't figure out why :-(

FWIW, same happens here, out-of-the-box 2.6.26-1 vanilla Debian. Booting
with 2.6.24-1 "fixes" this. Didn't try 2.6.25-1 yet.

Regards
- -- tomás
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)

iD8DBQFI/XFUBcgs9XrR2kYRAmATAJ96SU3oNvNWeJw0VOB7RMBcL66npQCfeZ1Q
YlMSHwJ5c/XxgH3sFpDuA94=
=a1Vq
-----END PGP SIGNATURE-----

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Mon, Oct 20, 2008 at 05:49:04PM -0300, Alvaro Herrera wrote:
> Hi,
>
> My Debian system (now running Linux 2.6.26) is no longer dumping core
> files, and I can't figure out why :-(

Tested now with 2.6.25-2. Coredumps still work there. I submitted it as
a bug:

<http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=502948>

Regards
- -- tomás
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)

iD8DBQFI/YmYBcgs9XrR2kYRAufMAJ9J4wdGWHSLwLPSd0mENDP5Nk/C6QCdEXOY
wFk4MDQl0HfaKAXmTMUuRZs=
=0J4V
-----END PGP SIGNATURE-----