Authentication as root should work instead
but it doesn’t in one strange situation:
when I add 100 or more users in some group, than I can’t “Enable changes” in “server settings GUI”
for example, I newly installed ubuntu-12.04-server-i386.iso and nomachine-enterprise-server-evaluation_4.0.369_2_i386.deb, then I create 100 users named “user1, user2, …, user100” which members of group sys by this script:
for i in seq 1 100
;do useradd -G sys user$i;done
after this I can’t “Enable changes” in “server settings GUI” by root or by “sudo user”