group administrator information and group-level passwords
group management tools
groupadd, groupmod, and groupdel
create, alter, and erase groups
groupadd command
adds entries to the group and gshadow files for each group added to the system
picks up default values from /etc/login.defs
Switches
-g (–gid)
Specifies the GID to be assigned to the group
-o (–non-unique)
Creates a group with a matching GID of an existing group. When two groups have an identical GID, members of both groups get identical rights on each other’s files. This should only be done in specific situations.
-r
Creates a system group with a GID below 1000
groupname
Specifies a group name
groupmod command
syntax of this command is very similar to the groupadd with most options identical.