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This is for users and groups that are defined by /etc/passwd and /etc/group et al.
Group creation
TODO: TBC
For non-system groups:
addgroup <group name>
Each user's primary group must exist before the user is created unless --user-group is specified on the useradd command.
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For a full Linux user, this example is as used at Saitri Savitri Bhavan on "archiver":
useradd --comment 'Vadivel' --create-home --groups archiver,sb-users vadivel--user-group
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