I found this on the net: http://www.scribd.com/doc/51889769/104/Primary-Versus-Secondary-Groups
One final note on groups is that it is important to understand the difference between the primary and secondary group. A user can only be a member of one primary group. The primary group is the group that any files they create will belong to by default. However,a user can be a member of multiple secondary groups.The primary group is the one that is listed in the /etc/passwd file along with the usersentry. Any other group that the user is a member of in /etc/group is considered to be a secondary group. And apparently a user needs to have a secondary group membership in group wheel to have sudo powers :) Mike On Sat, May 7, 2011 at 6:25 PM, Michael Sioutis <papito....@gmail.com> wrote: > Thanx a log for your replies :) > > I was also using the wrong command for the EXISTING user katia: > pico@hive:~$ sudo useradd -G guest katia > useradd: already a `katia' user > > Now: > pico@hive:~$ sudo usermod -G guest katia > pico@hive:~$ groupinfo guest > name guest > passwd * > gid 31 > members root katia > > So user 'katia' was in primary and now is in secondary too! > I can't say I understand the use of primary and secondary. > > I remember when I created user 'user' with useradd and entered 'wheel' > when prompted for the login group, > I didn't gain any sudo powers. (primary) > It was only untill I did: usermod -G wheel user that I gained sudo > powers (sencondary as I understand it). > > Mike > > On Sat, May 7, 2011 at 6:01 PM, Antoine Jacoutot <ajacou...@bsdfrog.org> wrote: >> On Sat, 7 May 2011, Stuart Henderson wrote: >> >>> Yes this is expected behaviour. /etc/group lists secondary group >>> memberships, /etc/passwd (and related files) list the primary groups. >>> >>> Most of the tools you're using to investigate group membership >>> (groupinfo, getent etc) only list secondary groups. >>> >>> "id katia" is showing first the primary group (gid=31), and then a >>> list of all groups this user has permissions for (either primary >>> or secondary). >> >> When you use useradd -g =uid, the primary group is created and the user >> put into it. >> >> # groupadd kiki >> # useradd kiki >> # groupinfo kiki >> name kiki >> passwd * >> gid 1001 >> members >> >> versus >> >> # useradd -g =uid kiki >> # groupinfo kiki >> name kiki >> passwd * >> gid 1001 >> members kiki >> >> -- >> Antoine
