updating users and groups (was Re: Announcing the release of Fedora 16 Beta!!)

[Ian Malone]

On 4 October 2011 16:50, Stephen Gallagher <sgallagh at redhat.com> wrote:
> On Tue, 2011-10-04 at 16:55 +0200, suvayu ali wrote:
>> Hi,
>>
>> On Tue, Oct 4, 2011 at 4:44 PM, Dennis Gilmore <dennis at ausil.us> wrote:
>> >    * System Accounts. Fedora now standardizes on login.defs as
>> > authority for UID/GID space allocation, and has moved boundary between
>> > system and user accounts from 500 to 1000 to match conventions
>> > followed by several other Linux distributions. Upgrading from a
>> > existing release will not be affected by this change and you can use
>> > kickstart to override this change during installation if necessary.
>> >
>>
>> When one preupgrades to F16 do the old 500+ user ids get converted to
>> 1000+, or is it expected the user will do this manually? In any case I
>> would be interested in knowing how to do this manually.
>
>
> No user IDs should EVER be altered automatically. This is unsafe,
> because it would change file access on the disk (and potentially result
> in a system that was inaccessible).
>
> You probably don't want to change this yourself either, but if you
> REALLY want to change IDs, you would need to use /usr/sbin/usermod to
> change the user's ID, then you would want to run a complicated 'find'
> command starting at the root of the filesystem to search for any file
> owned by the old UID and chown it. Then you'd have to repeat this for
> every user and every group. And then if you have data stored on
> removable disks or network shares, you need to handle those too...
>
> DO NOT DO THIS! It's only going to cause you problems.
>

No need for a (not that complex) find command, see the chown option:
--from=CURRENT_OWNER:CURRENT_GROUP, in conjunction with -R and -L this
makes life fairly easy. Genuinely removeable shares (i.e. those you
might take between computers) have issues with UIDs anyway and are
probably running something without it (e.g. NTFS), semi-removable
shares (e.g. USB drives that are always connected to your machine)
just need to be mounted when you do this.

You would still need to do it for all groups and users that you were
updating, I agree you really don't want to update an existing system
unless you have to (to make it play well with Ubuntu for instance).

-- 
imalone