You can use find command to find out all files that do not have any owners or do not belong to any user under Linux/UNIX/BSD operating systems.

Find file owned by user id 1050 (useful if you deleted user account):

# find / -uid 1050

Find out all files that are not owned by any user:

# find / -nouser

Find out all files that are not owned by any group:

# find / -nogroup

For example in real life on busy clustered hosting server some time we remove 5-10 users and for security reasons you need to find out all files are not owned by any user or group then you can type command:

# find / -nogroup -nouser

See also:

• How do I find all the files owned by a particular user or group?