For Ubuntu 14.04.1 LTS
Usage: usermod [options] LOGIN
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 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 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
-R, -root CHROOT_DIR directory to chroot into
-s, -shell SHELL new login shell for the user account
-u, -uid UID new UID for the user account
-U, -unlock unlock the user account
-v, -add-subuids FIRST-LAST add range of subordinate uids
-V, -del-subuids FIRST-LAST remvoe range of subordinate uids
-w, -add-subgids FIRST-LAST add range of subordinate gids
-W, -del-subgids FIRST-LAST remvoe range of subordinate gids
-Z, -selinux-user SEUSER new SELinux user mapping for the user account