gistfile1.txt

resources in cookbook:

user "dnscache" do
  uid 9997
  case node[:platform]
  when "ubuntu","debian"
    gid "nogroup"
  when "redhat", "centos"
    gid "nobody"
  else
    gid "nobody"
  end
  shell "/bin/false"
  home "/home/dnscache"
end

user "dnslog" do
  uid 9998
  case node[:platform]
  when "ubuntu","debian"
    gid "nogroup"
  when "redhat", "centos"
    gid "nobody"
  else
    gid "nobody"
  end
  shell "/bin/false"
  home "/home/dnslog"
end

user "tinydns" do
  uid 9999
  case node[:platform]
  when "ubuntu","debian"
    gid "nogroup"
  when "redhat", "centos"
    gid "nobody"
  else
    gid "nobody"
  end
  shell "/bin/false"
  home "/home/tinydns"
end

entries from /etc/passwd: 

dnscache:x:9997:65534::/home/dnscache:/bin/false
dnslog:x:9998:65534::/home/dnslog:/bin/false
tinydns:x:9999:65534::/home/tinydns:/bin/false

every chef-client run:
[Wed, 11 Feb 2009 13:58:42 -0700] INFO: Altered user[dnscache]
[Wed, 11 Feb 2009 13:58:42 -0700] INFO: Altered user[dnslog]
[Wed, 11 Feb 2009 13:58:42 -0700] INFO: Altered user[tinydns]

with added debug:

DEBUG: Processing user[dnscache]
DEBUG: user[dnscache] using Chef::Provider::User::Useradd
DEBUG: user[dnscache]: new: 9997, current: 9997
DEBUG: user[dnscache]: new: nogroup, current: 65534
DEBUG: Setting user[dnscache] gid to nogroup
DEBUG: Executing usermod -g 'nogroup' dnscache
DEBUG: Nothing to read on 'usermod -g 'nogroup' dnscache' STDOUT.
DEBUG: ---- Begin usermod -g 'nogroup' dnscache STDERR ----
DEBUG: usermod: no changes
DEBUG: ---- End usermod -g 'nogroup' dnscache STDERR ----
DEBUG: Ran  (usermod -g 'nogroup' dnscache) returned 0
INFO: Altered user[dnscache]
DEBUG: Processing user[dnslog]
DEBUG: user[dnslog] using Chef::Provider::User::Useradd
DEBUG: user[dnslog]: new: 9998, current: 9998
DEBUG: user[dnslog]: new: nogroup, current: 65534
DEBUG: Setting user[dnslog] gid to nogroup
DEBUG: Executing usermod -g 'nogroup' dnslog
DEBUG: Nothing to read on 'usermod -g 'nogroup' dnslog' STDOUT.
DEBUG: ---- Begin usermod -g 'nogroup' dnslog STDERR ----
DEBUG: usermod: no changes
DEBUG: ---- End usermod -g 'nogroup' dnslog STDERR ----
DEBUG: Ran  (usermod -g 'nogroup' dnslog) returned 0
INFO: Altered user[dnslog]
DEBUG: Processing user[tinydns]
DEBUG: user[tinydns] using Chef::Provider::User::Useradd
DEBUG: user[tinydns]: new: 9999, current: 9999
DEBUG: user[tinydns]: new: nogroup, current: 65534
DEBUG: Setting user[tinydns] gid to nogroup
DEBUG: Executing usermod -g 'nogroup' tinydns
DEBUG: Nothing to read on 'usermod -g 'nogroup' tinydns' STDOUT.
DEBUG: ---- Begin usermod -g 'nogroup' tinydns STDERR ----
DEBUG: usermod: no changes
DEBUG: ---- End usermod -g 'nogroup' tinydns STDERR ----
DEBUG: Ran  (usermod -g 'nogroup' tinydns) returned 0
INFO: Altered user[tinydns]