Description of problem:

A customer had a 'rpc' user (not UID=32) on the system, but the existing 'rpc' user was deleted by the installation of rpcbind package without any message.

We found a fedora documentation about packaging, and it says that any user account should not be deleted during the package installation.

https://fedoraproject.org/wiki/Packaging:UsersAndGroups?rd=Packaging/UsersAndGroups

In rpcbind.spec:
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%pre

# Check the validity of the rpc uid and gid.
# If they don't exist, create them
# If they exist but are the wrong value, remove them 
#   and recreate them with the correct value
# If they exist and are the correct value do nothing
rpcid=`getent passwd rpc | cut -d: -f 3`
if [ -n "$rpcid" -a "$rpcid" != "32" ]; then
        /usr/sbin/userdel  rpc 2> /dev/null || :
        /usr/sbin/groupdel rpc 2> /dev/null || :
fi
if [ -z "$rpcid" -o "$rpcid" != "32" ]; then
        /usr/sbin/groupadd -o -g 32 rpc > /dev/null 2>&1
        /usr/sbin/useradd -o -l -c "Rpcbind Daemon" -d /var/cache/rpcbind -g 32 \
        -M -s /sbin/nologin -u 32 rpc > /dev/null 2>&1
fi
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It forces to have the 'rpc' account with UID=32. If the UID is not 32, it removes it and create another 'rpc' account with UID=32.

If the above fedora documentation is correct, it should not remove the existing 'rpc' account during the installation. 

As an example of another package, 'httpd' also creates a user account 'apache'.
But, if the user account 'apache' exists, it never remove the existing account.

Version-Release number of selected component (if applicable):
Red Hat Enterprise Linux 6