For some strange reason I am no longer able to create groupnames or usernames (with useradd and groupadd) that contain a dot. Uptill now it was possible to create user&groupnames like c.smith but now I get these errors: [root at server etc]# useradd c.smith useradd: invalid user name 'c.smith' [root at server1 etc]# groupadd c.smith groupadd: c.smith is a not a valid group name Anything without a dot works without problems. The box is a (fully updated) CentOS 3.6 x86_64 box with Dual Opteron cpu. Thanks for any hints!