Index: reserved-usernames
===================================================================
--- reserved-usernames	(revision 0)
+++ reserved-usernames	(revision 0)
@@ -0,0 +1,94 @@
+# Static users from base-passwd/passwd.master.
+root
+daemon
+bin
+sys
+sync
+games
+man
+lp
+mail
+news
+uucp
+proxy
+www-data
+backup
+list
+irc
+gnats
+nobody
+
+# Other static groups from base-passwd/group.master.
+adm
+tty
+disk
+kmem
+dialout
+fax
+voice
+cdrom
+floppy
+tape
+sudo
+audio
+dip
+operator
+src
+shadow
+utmp
+video
+sasl
+plugdev
+staff
+users
+nogroup
+
+# Reserved usernames listed in base-passwd/README.
+netplan
+ftn
+mysql
+tac-plus
+alias
+qmail
+qmaild
+qmails
+qmailr
+qmailq
+qmaill
+qmailp
+asterisk
+vpopmail
+vchkpw
+
+# Other miscellaneous system users/groups created by common packages.
+Debian-exim
+admin
+bind
+crontab
+cupsys
+dhcp
+dictd
+ftp
+fuse
+gdm
+# "hal" is a bit annoying, because it's also a not uncommon human name. It's
+# haldaemon in Ubuntu ...
+hal
+haldaemon
+hplilp
+identd
+klog
+lpadmin
+messagebus
+netdev
+powerdev
+saned
+sbuild
+scanner
+slocate
+ssh
+sshd
+ssl-cert
+statd
+syslog
+tftpd
Index: debian/user-setup.install
===================================================================
--- debian/user-setup.install	(revision 40628)
+++ debian/user-setup.install	(working copy)
@@ -2,3 +2,4 @@
 user-setup-ask usr/lib/user-setup
 user-setup-apply usr/lib/user-setup
 functions.sh usr/lib/user-setup
+reserved-usernames usr/lib/user-setup
Index: debian/user-setup-udeb.templates
===================================================================
--- debian/user-setup-udeb.templates	(revision 40628)
+++ debian/user-setup-udeb.templates	(working copy)
@@ -80,6 +80,12 @@
  a lower-case letter, which can be followed by any combination of numbers
  and more lower-case letters.
 
+Template: passwd/username-reserved
+Type: error
+_Description: Reserved username
+ The user name you entered (${USERNAME}) is reserved for use by the system.
+ Please select a different one.
+
 Template: passwd/user-password
 Type: password
 _Description: Choose a password for the new user:
Index: debian/changelog
===================================================================
--- debian/changelog	(revision 40628)
+++ debian/changelog	(working copy)
@@ -1,3 +1,14 @@
+user-setup (1.6) UNRELEASED; urgency=low
+
+  * Detect and error out on reserved usernames, i.e. those that are already
+    used by some parts of the system. Unfortunately there's no particularly
+    straightforward way to identify a reserved username, and the only way I
+    can think of is to maintain a blacklist; so I've collated this from the
+    base-passwd master files and those user and group names I found on some
+    of my systems. Feel free to extend this as the need arises.
+
+ -- Colin Watson <cjwatson@debian.org>  Wed, 13 Sep 2006 21:55:40 +0100
+
 user-setup (1.5) unstable; urgency=low
 
   [ Frans Pop ]
Index: debian/user-setup-udeb.install
===================================================================
--- debian/user-setup-udeb.install	(revision 40628)
+++ debian/user-setup-udeb.install	(working copy)
@@ -1,4 +1,5 @@
 user-setup-ask usr/bin
 user-setup-apply usr/bin
 functions.sh usr/lib/user-setup
+reserved-usernames usr/lib/user-setup
 finish-install.d usr/lib
Index: user-setup-ask
===================================================================
--- user-setup-ask	(revision 40628)
+++ user-setup-ask	(working copy)
@@ -143,6 +143,15 @@
 				continue
 			fi
 			
+			if ! grep -v '^#' /usr/lib/user-setup/reserved-usernames | \
+			     grep -q "^$USER$"; then
+				db_fset passwd/username seen false
+				db_fset passwd/username-reserved seen false
+				db_input critical passwd/username-reserved
+				STATE=3
+				continue
+			fi
+
 			db_get passwd/user-password-crypted || true
 			if ! test "$RET" ; then
 				db_input critical passwd/user-password || true