Add users to user groups and user groups in Linux

Add users to user groups and user groups in Linux

Http://blog.csdn.net/pursue168/article/details/6443046

To add a user to a user group, do not directly use: usermod-G groupA
This will cause you to leave other user groups and act only as a member of the groupA user group. -A option should be added: usermod-a-G groupA user

(FC4: usermod-G groupA, groupB, groupC user)-a indicates append, that is, adding yourself to the user group groupA without leaving other user groups.
Options:-c, -- comment COMMENT new value of the GECOS field-d, -- home HOME_DIR new home directory for the user account-e, -- expiredate EXPIRE_DATE set account expiration date to EXPIRE_DATE-f, -- inactive INACTIVE set password inactive after expiration to INACTIVE-g, -- gid GROUP force use GROUP as new primary group-G, -- groups GROUPS new list of supplementary GROUPS-a, -- append the user to the supplemental GROUPS mentioned by the-G option without removing him/her from other groups-h, -- help display this help message and exit-l, -- login NEW_LOGIN new value of the login name-L, -- lock the user account-m, -- move-home move contents of the home directory to the new location (use only with-d)-o, -- non-unique allow using duplicate (non-unique) UID-p, -- password PASSWORD use encrypted password for the new password-s, -- shell SHELL new login shell for the user account-u, -- uid UID new UID for the user account-U, -- unlock the user account

 

Run the command $ groups user to view the group to which the user belongs.

Or view the file: $ cat/etc/group.