Tuesday, December 6, 2011

Solaris: coreadm core file management

Using the Solaris coreadm utility to control core file generation

Solaris has shipped with the coreadm utiltiy for quite some time, and this nifty little utility allows you to control every facet of core file generation. This includes the ability to control where core files are written, the name of core files, which portions of the processes address space will be written to the core file, and my favorite option, whether or not to generate a syslog entry indicating that a core file was generated.
To begin using coreadm, you will first need to run it wit the “-g” option to specify where core files should be stored, and the pattern that should be used when creating the core file:
coreadm -g /var/core/core.%f.%p
Once a directory and file pattern are specified, you can optionally adjust which portions of the processes address space (e.g., text segment, heap, ISM, etc.) will be written to the core file. To ease debugging, I like to configure coreadm to dump everything with the”-G all” option:
coreadm -G all
Since core files are typically created at odd working hours, I also like to configure coreadm to log messages to syslog indicating that a core file was created. This can be done by using the coreadm “-e log” option:
coreadm -e log
After these settings are adjusted, the coreadm “-e global” option can be used to enable global core file generation, and the coreadm utility can be run without any arguments to view the settings (which are stored in /etc/coreadm.conf):
coreadm -e global
global core file pattern: /var/core/core.%f.%p
     global core file content: all
       init core file pattern: core
       init core file content: default
            global core dumps: enabled
       per-process core dumps: enabled
      global setid core dumps: disabled
 per-process setid core dumps: disabled
     global core dump logging: enabled
Once global core file support is enabled, each time a process receives a deadly signal (e.g., SIGSEGV, SIGBUS, etc.):
$ kill -SIGSEGV 4652
A core file will be written to /var/core:
ls -al /var/core/*4652
-rw-------   1 root     root     4163953 Mar  9 11:51 /var/core/core.inetd.4652
And a message similar to the following will appear in the system log:
Mar 9 11:51:48 fubar genunix: [ID 603404 kern.notice] NOTICE: core_log: inetd[4652] core dumped: /var/core/core.inetd.4652
This is an amazingly useful feature, and can greatly simplify root causing software problems.