I want my core dumps

Posted on 2006-05-18
Medium Priority
Last Modified: 2008-02-01
I've got a server program running on Linux (kernel 2.6.13 x86_64), and my problem is that when the program catches SIGSEGV (segmentation fault) and then reacts to it by calling abort(), no core dump is written. There's no limit on core file size, and since server programs are pain in the behind to debug, I'd rather like to see what the dump has to say. How can I ensure that the dump is written properly (or inproperly in the case the system is for some reason "supposed" to not write a core dump)?

[root ~]# ulimit -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
file size               (blocks, -f) unlimited
pending signals                 (-i) 32251
max locked memory       (kbytes, -l) 32
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 32251
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

[root ~]# ls -la .
drwxrwx-w-  3 root root     83 May 17 13:48 .
Question by:sanctimonious

Expert Comment

ID: 16709858
You might want to use a serial console to catch the oops message.

Expert Comment

ID: 16715149
One reason it can't write a core dump is if the program CAN'T write a file there (for example, on NFS mounts which don't allow root rights).

Can you generate the problem at will?  I guess hit it with a kill -SIGSEGV.

You may want to hook it up to strace when you're doing this...also look at the current directory
(and see if it is writable and exists).
LVL 43

Accepted Solution

ravenpl earned 2000 total points
ID: 16715646
man prctl # flag PR_SET_DUMPABLE
and make sure current working directory for process is writeable by euid of the process.
Also check out /proc/sys/kernel/core_pattern (it may use pattern reffering another directory, which is unwriteable for process)

Author Comment

ID: 16716920
You, sir, are a scholar and a gentleman. Prctl() was right on the money.

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