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An important reason why yoastras are
created is for file ownership, for permissions.

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So how does it work? Well, access to
files on Linux is based on file ownership.

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And when a user creates a file
on Linux, that user becomes a file owner.

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Every Linux user is a member of at least
one group, and while creating a file on Linux,

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that group will will become the group owner. We
call that group, by the way, the primary group.

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Because of group ownership, every user must
be a member of at least one group.

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And most Linux distributions are using private groups for the
primary group. And that means that while creating a user,

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a group with the name of the user is created
and the user is the only member of that group.

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That doesn't sound very useful, but it's mainly because
of the requirement that users must be a member of

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a group. And you want this group membership to
be as secure as possible. Let me show you.

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So I'm going to use sudo su
Linda. That's a little trick that allows

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me to use my sudo privileges
to open a shell as user Linda.

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And now I'm in my User Linda
shell. Who am I confirming? That ID is

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showing my current configuration where we can
see that the user ID1001 has the name

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Linda. The GID1001 is the primary
group, which also has the name Linda.

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And here groups is a list of all groups that user
Linda is a member of. That's not very impressive, but that's

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a default situation. Create a user. The user will become
a member of a group with the name of that user.

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Now I'm using Touch lynda file and what do
we see when we use LS L? We see

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that lynda file is owned by user Linda and
group owned by the group Linda. And that's how

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ownership is used when files are created. More
about ownerships and permissions will follow in later videos.

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Let me use Exit because I don't have
to be in the user Linda shell anymore.