Its fine. The file (I am assuming its in your /root directory?) is a core dump generated after a segmentation fault. There is a program (or at least, there should be) on your server that is part of the default Linux installation for parsing the file to determine the cause of the crash, called gdb. Or, you can simply delete the file.

(A search for "core.1234" in quotes will give you a lot of resources about reading and using these files.)

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