What does the "number" in the owner field of files signify in linux?

Question

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?

Solution 1

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/passwd or /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/group and /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 chown and chgrp respectively.

Solution 2

It means that:

1. The file is owned by user:group 515:515
2. the user and group ids 515 are not defined in /etc/passwd or /etc/group as assigned to a specific user and group.

Solution 3

It means that either there is no user and group with those IDs, or that their names are too long to display entirely in that field.

Solution 4

It is the user or group id of users.

The mapping to user names is in /etc/passwd (for user ids) or /etc/groups (for group ids)

See

man id
man usermod  # (the -u option)
man groupmod # (the -g option)
man shadow   # (to know why you shouldn't meddle with /etc/passwd directly)

View more solutions

Comments

[Mel]

Side note: Most common scenario for orphan user/groups is extraction from an archive.