why there is a large file named core in wpmu's directory?

Question

why the file named core is here? can i delete it?

ls -lh
total 37M
-rw-rw-r--  1 hugemeow pg   16 2012-03-04 04:22 a.php
-rw-------  1 hugemeow pg  30M 2012-10-16 10:41 core   // this is the large file
-rw-r--r--  1 hugemeow pg  397 2012-01-26 07:53 index.php
-rw-r--r--  1 hugemeow pg  17K 2012-01-26 07:53 license.txt
-rw-r--r--  1 hugemeow pg 9.0K 2012-01-26 07:53 readme.html
-rw-rw-r--  1 hugemeow pg 7.4M 2012-09-22 02:27 tags
-rw-r--r--  1 hugemeow pg 4.2K 2012-01-26 07:53 wp-activate.php
drwxr-xr-x 10 hugemeow pg 4.0K 2012-10-11 08:37 wp-admin
-rw-r--r--  1 hugemeow pg  40K 2012-01-26 07:53 wp-app.php
-rw-r--r--  1 hugemeow pg  274 2012-01-26 07:53 wp-blog-header.php
-rw-r--r--  1 hugemeow pg 3.9K 2012-01-26 07:53 wp-comments-post.php
-rw-r--r--  1 hugemeow pg 3.2K 2012-01-26 07:53 wp-config-sample.php
-rw-r--r--  1 hugemeow pg 3.6K 2012-10-11 08:37 wp-config.php
-rw-r--r--  1 hugemeow pg 3.5K 2012-03-14 17:08 wp-config.php_bak0
drwxr-xr-x  8 hugemeow pg 4.0K 2012-12-01 04:12 wp-content
-rw-r--r--  1 hugemeow pg 2.7K 2012-01-26 07:53 wp-cron.php
drwxr-xr-x  8 hugemeow pg 4.0K 2012-09-22 02:35 wp-includes
-rw-r--r--  1 hugemeow pg 2.0K 2012-01-26 07:53 wp-links-opml.php
-rw-r--r--  1 hugemeow pg 2.5K 2012-01-26 07:52 wp-load.php
-rw-r--r--  1 hugemeow pg  28K 2012-01-26 07:53 wp-login.php
-rw-r--r--  1 hugemeow pg 7.6K 2012-01-26 07:53 wp-mail.php
-rw-r--r--  1 hugemeow pg  413 2012-01-26 07:53 wp-pass.php
-rw-r--r--  1 hugemeow pg  334 2012-01-26 07:53 wp-register.php
-rw-r--r--  1 hugemeow pg 9.7K 2012-01-26 07:53 wp-settings.php
-rw-r--r--  1 hugemeow pg  19K 2012-01-26 07:53 wp-signup.php
-rw-r--r--  1 hugemeow pg 3.7K 2012-01-26 07:52 wp-trackback.php
-rw-r--r--  1 hugemeow pg 3.2K 2012-01-26 07:53 xmlrpc.php


file core
core: ELF 64-bit LSB core file x86-64, version 1 (SYSV), SVR4-style, from 'php5.cgi'

Answer 1

Files named "core" are created when some OS process crashes. In your case it was likely a crash of the php interpreter.

These files being memory dumps are used to debug the process "postmortem" - e.g. to check in which function did it fail, so it is perfectly safe to delete them if you are not going to debug the issue.

In fact, on many systems there is a setting to not allow creation of core files by default.

BTW, the date of the file indicates the date of the original process crash.

More info: core files