I copied many files to my new linux host. I see that all files have the owner and group both set to
515. What does that mean?
You probably did a copy that preserved the original group and owner of these files. Within linux internally the owner and group is basically just an id (in your case, the number 515). This id is then mapped on a group and user name listed in
/etc/group. You will see that in those files, you can find the name of the user and also the id used for that specific user and group.
Most likely in the
/etc/passwd, the id "515" is not listed, and for this reason the id itself is shown.
You can change the ower and group to an existing owner and group with the commands