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- So now that you know
how to work with users,

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you should also know
how to work with groups.

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So in order to create
groups, you use groupadd

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followed by the name of the group

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and then you can add users to a group

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as a secondary group using
usermod -aG groupname username.

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Let me just show you.

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Now, the first that we should explore

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is a statement as a secondary group.

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What is the thing if I use id on bill

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to explore the properties of user bill,

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then we can see that
while I created user bill,

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useradd has also created a
group with the name bill.

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We can even verify

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if I use grep bill on etc group.

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Etc group is where the groups are stored.

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You can see that group bill is created.

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So if it's for the primary group

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you don't have to do anything.

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If it's for the secondary group

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you do need to do something.

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So sudo groupadd sales, for instance

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is creating a group with the name sales.

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We can verify that.

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Grep sales in etc group and yay,

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the group has been created,

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but now I want users to be a member.

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Then I need usermod.

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So sudo usermod -aG sales bill

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is doing what?

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This is adding user bill as
a member to the group sales.

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Now this does not change
anything about the ownership.

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Let me show you sudo su - bill.

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I have no password for bill.

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So this is the only way
that I can easily get

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into a shell is user bill.

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And let me create a file
with the name bilfile

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and ls -l and there we can
see ownership is still set

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to bill and bill.

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Secondary groups are cool,

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but secondary groups are
mainly to grant permissions

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to additional items.

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They are not used for
ownership by default.