I'm moving files over from my old server to my new server. By the time I'm doing it for real (as opposed to just testing) I'll have all the "user" users (the non-system users, i.e. >= 1000) created on the new server. My only fear is that I have some file that I'm moving over in the home directory that will belong to one of these users (say apache for instance) that doesn't exist on the new server. I'm using
rsync -az -e ssh src dest
as user on the new server to do the copying. It does preserve the usernames (as opposed to ids) for the users that exist. However instead of complaining about non-existent users, it just falls back on the numeric ids if the user isn't found. The behavior seems to be as described in this paragraph from the man page:
If a user or group has no name on the source system or it has no match on the destination system, then the numeric ID from the source system is used instead. See also the comments on the "use chroot" setting in the rsyncd.conf manpage for information on how the chroot setting affects rsync’s ability to look up the names of the users and groups and what you can do about it.
While I haven't read the entire man page word for word, what I have read doesn't offer me any options to complain about non-existent users. What is the best way to make sure that whatever users exists as owners/groups of files under a directory (say /home) exist on the new machine. If it's not doable with rsync, what's the best way to get a list of all the users/groups that exist so I can manually check that they exist on the new machine, or fix them before copying them.
How do I make sure that after I run rsync, none of the files have been copied using numeric ids instead of name ids?