Core dumps are files the system creates when a process running in memory does not finish. The portion of memory that the process was using is then dumped to a file. This can be quite helpful when debugging your scripts. Core dumps typically have a file name like: core.5876
Reviewing Core Dump Files on VPS or Dedicated Servers
For most users, getting usable information from a core dump file can be difficult. If you are a VPS or Dedicated customer with command line (shell) access, most of the information in the core dump can be found by running either one of these two commands:
gdb -c core.####
strings core.####
Reviewing Core Dump Files on Shared Servers
If you are on a shared hosting package, for security reasons you do not have access to the command line. For our shared customers, we’ve created a basic PHP script that uses the commands above to allow you to find any core dump files in your account. The script can be found here:
https://www.inmotionhosting.com/support/files/scripts/coredumpcheck.txt
Please note! For security reasons, please either delete this file after using it OR password protect it.
- Upload the coredumpcheck.txt file to the folder where you want to view core dumps.
- Rename the file to coredumpcheck.php
- Access coredumpcheck.php file in your browser. For example, if you have core dumps in your public_html folder then you would go to https://example.com/coredumpcheck.php
- The script will list all the core dumps in the current directory. Click any of the file names to view more details about the core dump.Â
- Look under the “RUNNING: gdb -c core.30387” heading to find the script that is causing the problem. It will look something like:
Core was generated by ‘/usr/bin/php /home/training/public_html/t2c_escalation/escalatet2s.php’.
We’ve highlighted this in the screenshot below:
Resolving Core Dumps
Core dumps are advanced in nature. It’s best practice to contact your web developer with the information that you have using the coredumpcheck.php script. If you are using a CMS such as WordPress, Joomla, or Drupal and the core dump is being caused by a plugin or module, your can disable or remove that module to resolve the issue.
I am finding a common thread in my support searches that people with InMotion hosting who update to WordPress 4.6 are the ones having Core Dump issues. I have updated on several other hosts and not had the issue crop up. Could it possibly be an incompatibility in your database or PHP settings to the new update?
I’d really prefer to have my client in the most secure version of WordPress, but the core dumps and the code suggested for how to root them out only points to core WordPress files that aren’t being manually updated by me. Help?
Hello Emmanuel,
The article is provided to help people understand the reason for core dumps and defines what they are. We do not provide the next step in debugging your website, as core dumps are typically caused by issues with your website code. If you are not sure what to do at this point, then you will need to consult with a web developer to help find the issue causing the core dumps in your code.
If you have any further questions or comments, please let us know.
Regards,
Arnel C.
When I try to run gdb, I get this:
-bash:
gdb: command not foundYou may have to install the “gdb” command as the root user, or submit a ticket requesting it be installed on your server.
Thank you,
John-Paul
So I placed the coredumpcheck.php file in my public_html folder (https://*mysite*.com/coredumpcheck.php) and got this:
Core was generated by `whois actprepvideos.com’.
In this article, it gives an example like this:
Core was generated by ‘/usr/bin/php /home/training/public_html/t2c_escalation/escalatet2s.php’.
That example clearly shows where the issue is originating from – the exact folder and file. However, in my case, i cant derive anything from the information it is providing.
Can you please explain what Core was generated by `whois actprepvideos.com’ means?
Whois is a command ran through the command line. If its one core dump, I’d say you could ignore it. Is this an ongoing issue?
I ran the checker and got this: Core was generated by `whois actprepvideos.com’
What does that even mean?
Nice post,
The command is gdb. not gbd. Please change.
————
gbd -c core.####
strings core.####
————
Thanks,.
Hello Vipin,
I have updated the article, thank you for catching that and letting us know as we are all human.
Best Regards,
TJ Edens
Hi,
It seems that from August 7th to August 16th this year my site created over 200 core dumps. Following the instructions above, this is all that I got in the “Running” part:
====
GNU gdb (GDB) Red Hat Enterprise Linux (7.2-83.el6)
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type “show copying”
and “show warranty” for details.
This GDB was configured as “x86_64-redhat-linux-gnu”.
For bug reporting instructions, please see:
.
(gdb) Hangup detected on fd 0
error detected on stdin
======
So, what does all that mean? What was causing the core dumps? And howcome it seems to have resolved itself? any suggestions or ideas?
This is a wordpress site that I basically haven’t touched for a long time.
Thanks
Noel
Hello Noel,
There are a number of reasons that you can get core dumps, but it may be a result of a temporary issue like a corrupted database table or entry. So, if the table is repaired, an issue is corrected with maintenance on the site, or a server fixes a conflict, then the core dumps may appear to be self-corrected. I hope that helps to explain it.
If you have any further questions or comments, please let us know.
Regards,
Arnel C.
It appears as though when I review the dump my issue is being caused by the wp-cron.php file. This is a core WordPress file and I have never modified this file. Any suggestions on how to resolve this? The files are almost 100MB in size and are not created daily, but every other day approximately.
Hello Sean,
That is weird that you would be getting core dumps from that file. However you can disable that function in wordpress by disabling the wp-cron.php file.
Best Regards,
TJ Edens
Great post. Exactly what I needed.
Question: How long does it take te script to read the core dump? The dump is about 166Mb.
Hello Ralf,
Thank you for contacting us. It is difficult to say, since it depends on y our exact server environment and the amount of tasks it is performing at time you run the script.
But, generally speaking, it shouldn’t take long since it is just dumping a text file from memory.
Thank you,
John-Paul
Please update this article with the updated information now that shared servers allow command line access! TYVM!
thank you for sharing code development ……….
I’m happy I found your post, at first I thought it was a hack because whenever I delete the files, after sometime I found them again and occupying all my hosting space.
Hopefully with this information I will solve it.