Creating core dumps to help analyse VirtualBox crashes

A core dump is a technical term for a file containing detailed information about the state of an application at a given time in a form which developers can make use of. They are particularly helpful for tracking down the reasons for application crashes, which is why many systems let you tell them to automatically create a core dump at the moment when a crash occurs.

How to create a core dump on Linux

The procedure for creating a core dump is similar on most Linux systems, but on Ubuntu it is slightly different due to the Ubuntu crash reporting tool (Apport).

To create a core dump on an Ubuntu system

create a file called ".config/apport/settings" in your home directory with the contents

[main]
unpackaged=true

and run VirtualBox. Any crashes of VirtualBox after you have created the file will cause a crash report to be created in /var/crash with a name like "_usr_lib_virtualbox_VirtualBox.1000.crash". Do not accept the offer to "send a crash report to Launchpad". You can extract the core file using the "apport-unpack" tool, or if you are unsure you can just send us the full crash report file. To stop crash files being created for non-system applications delete the file that you created again.

To create a core dump on non-Ubuntu systems

start VirtualBox from a command line (e.g. xterm):

$ ulimit -c unlimited
$ sudo su
# echo -n 1 > /proc/sys/kernel/core_uses_pid
# echo -n 1 > /proc/sys/fs/suid_dumpable
# exit
$ VirtualBox

or better start the VM directly:

$ ulimit -c unlimited
$ sudo su
# echo -n 1 > /proc/sys/kernel/core_uses_pid
# echo -n 1 > /proc/sys/fs/suid_dumpable
# exit
$ /usr/lib/virtualbox/VirtualBox -startvm VM_NAME

Ensure that no startup script (~/.bashrc, ~/.bash_profile, ~/.profile) contains an instruction like ulimit -c 0 as the limit cannot be increased once it was set to zero.

Starting with version 2.0.0, the VirtualBox processes are started suid root, that is, with permissions to do things that "normal" applications cannot. This is the reason for the

$ sudo su
$ echo -n 1 > /proc/sys/fs/suid_dumpable
$ exit

before starting the VM/GUI (note that sudo echo will not do what we want here).

When VirtualBox or one of its processes crashes, a file core.<pid> is created in the current directory. Be aware that core dumps can be very huge. Please compress the file before submitting it to a bug report. Or better don't attach the file to a report. Note that this core dump can contain a memory dump of your guest which can include sensitive information. Send it to frank _dot_ mehnert _at_ oracle _dot_ com if the compressed file is smaller than 5MB. Upload it to ftp.oracle.com:/appsdev/incoming and contact me directly otherwise to tell me the file name of the uploaded core dump.

If several core files are created, you can check which process created them using the command

$ file core.<pid>

to be sure of the right one to send.

How to create dumps on Mac OS X

To create a core dump on Mac OS X, start VirtualBox from a command line:

$ ulimit -c unlimited
$ VirtualBox

or better start the VM directly:

$ ulimit -c unlimited
$ /Applications/VirtualBox.app/Contents/MacOS/VirtualBox -startvm VM_NAME

Ensure that no startup script (~/.bashrc, ~/.bash_profile, ~/.profile) contains an instruction like ulimit -c 0 as the limit cannot be increased once it was set to zero.

Alternatively (for Finder & launchpad)

$ launchctl limit core unlimited

or for permanent effect the same could be specified in $HOME/.launchd.conf or /etc/launchd.conf.

The core files can be found in the /cores folder.

How to create dumps on Solaris

To get core on Solaris host run the following command as root

# coreadm -g /var/cores/core.%f.%p -i core.%f.%p \
  -e global -e process -e global-setid -e proc-setid -e log

The cores will now be placed in /var/cores/ folder with the global dumps will go into /var/crash/<hostname>

System core dumps need to be enabled via dumpadm. The important thing is to have "Savecore enabled" to "yes" (use dumpadm -y). The config. should look something like this:

# dumpadm
      Dump content: kernel pages
       Dump device: /dev/zvol/dsk/rpool/dump (dedicated)
Savecore directory: /var/crash/myhostname
  Savecore enabled: yes
   Save compressed: on

Forcing VirtualBox to terminate with a core dump

Sometimes it is required to force a VirtualBox process to terminate, for example, a VM hangs for some unknown reason. On Linux, this can be done as follows:

$ ulimit -c unlimited
$ sudo echo -n 1 > /proc/sys/fs/suid_dumpable
$ /usr/lib/virtualbox/VirtualBox -startvm VM_NAME &
$ pidof VirtualBox
7145
$ kill -4 7145

As an alternative to kill you can do

$ pidof VirtualBox
7145
$ gcore 7145

On Mac OS X:

$ ulimit -c unlimited
$ /Applications/VirtualBox.app/Contents/MacOS/VirtualBox -startvm VM_NAME &
$ ps aux|grep VirtualBox
... 7145 ... VirtualBox ...
$ kill -4 7145

On Solaris:

# ulimit -c unlimited
# /opt/VirtualBox/amd64/bin/VirtualBox -startvm VM_NAME &
# ps -ef|grep VirtualBox
... 7145 ... VirtualBox ...
# kill -4 7145

You can find result core file according location specified in coreadm

# coreadm

Passing the signal number 4 (SIGILL) is essential! The same applies to the alternative frontends VBoxHeadless and VBoxSDL.

Minidumps on Windows

Please visit this ​Microsoft site for more details about minidumps
Please visit the ​Microsoft Performance Team blog for more details about Application crash dumps

User mode crash dumps on Windows Vista and Windows 7

The section To collect user-mode dumps of the ​Microsoft site explains how to enable user mode dumps on Windows Vista and Windows 7
More detailed information about collecting user-mode dumps is available on the ​MSDN site