====== Core files Management ======

Check the progam associated to a core file, and all dependent libraries:
<cli prompt='#'>
root@nim /root # /usr/lib/ras/check_core /export/lpp_source/base-aix61tl6/core
/usr/lib/libc.a
/usr/lib/libodm.a
/usr/lib/libinstall.a
/usr/lib/libcfg.a
/usr/lib/libcrypt.a
/usr/lib/nls/loc/en_US
/usr/lib/libi18n.a
/usr/lib/libiconv.a
installp
</cli>

The following file is not a core file, just a file named "core":
<cli prompt='#'>
root@nim /root # /usr/lib/ras/check_core /etc/security/aixpert/core
check_core:: Error 0
</cli>

=== Best practice: centalize core ===

In order to centralize cores at one place

- Create a dedicated filesystem, with full permissions for everybody
<cli prompt='#'>
root@nim /root # mklv -tjfs2 -y corelv rootvg 1G
root@nim /root # crfs -vjfs2 -m /var/core -d corelv -Ayes -a log=INLINE
root@nim /root # mount /var/core
root@nim /root # chmod 777 /var/core
</cli>

===== User core path =====

- Change the path to centralize all cores for all user into /var/core; this command will set the default parameters for cores in /etc/security/user. User cores are persistent parameters.
<cli prompt='#'>
root@nim /root # lscore
compression: off
path specification: off
corefile location: not set
naming specification: off
root@nim /root # chcore -c on -p on -l /var/core -n on -d
root@nim /root # lscore
compression: on
path specification: on
corefile location: /var/core
naming specification: on
</cli>

===== syscorepath =====

- While it's not persistent, system core have to be set at every start by adding an entry into /etc/inittab
<cli prompt='#'>
root@nim /root # syscorepath -g

root@nim /root # echo '#!/bin/ksh
# Set core path for system
if [[ "$(uname -W)" == "0" ]]
then
  if [ -d /var/core ]
  then
    syscorepath -p /var/core
    if [ $? -eq 0 ]
    then
      echo "syscorepath OK"
    fi
  else
    echo "**** ERROR /var/core doesn t exist"
  fi
fi
' > /etc/rc.syscore
root@nim /root # chmod +x /etc/rc.syscore
root@nim /root # mkitab "syscore:23:once:/etc/rc.syscore > /dev/console 2>&1"
root@nim /root # /etc/rc.syscore
root@nim /root # syscorepath -g
/var/core
</cli>

===== Check core size per user =====

- If required change user core parameter to take the default value. Here for example for the root user.
<cli prompt='#'>
root@nim /root # cat /etc/security/limits
....
default:
        fsize = 2097151
        core = 2097151
        cpu = -1
        data = 262144
        rss = 65536
        stack = 65536
        nofiles = 2000

root:
        fsize = -1
        core = 0
        data = 524288
root@nim /root # chuser -R files -a core='' root
</cli>

 If enabled, fullcore will increase the size of each core file written on the system by including additional information such as shared memory segments that might be needed in order to find the cause of a problem, and additional data needed when debugging multi-threaded programs.

To enable full core:
  chdev -l sys0 -a fullcore=true
===== Generate a core file =====

Allow root user to produce cores, if ulimit -c is 0 then no core allowed
<cli prompt='#'>
root@nim /root # ulimit -c
0
root@nim /root # lsuser -a core root
0
root@nim /root # ulimit -c 2097151
root@nim /root # while true
do
sleep 14
done &
[1]     8257538
root@nim /root # kill -3 8257538
root@nim /root # ls -l /var/core
total 48
-rw-------    1 root     system        11159 Oct 18 12:02 core.8257538.18100246.Z
drwxr-xr-x    2 root     system          256 May 19 2016  lost+found
[1] + Quit(coredump)           while true;do;sleep 14;done &
root@nim /var/core # uncompress /var/core/core.8257538.18100246.Z
root@nim /var/core # /usr/lib/ras/check_core /var/core/core.8257538.18100246
/usr/lib/libc.a
/usr/lib/libiconv.a
/usr/lib/libcrypt.a
/usr/lib/nls/loc/en_US__64
/usr/lib/libi18n.a
/usr/ccs/bin/usla64
ksh93
</cli>