User & Group Creation (Demo)
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>> Hey there, Cybrarians.
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Welcome back to the Linux+ course here at Cybrary.
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I'm your instructor Rob Gals.
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In today's lesson, we're going to be
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discussing user and group creation.
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Upon completion of today's lesson,
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you're going to be able to understand
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user and group creation and use
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the useradd and groupadd commands.
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The useradd command is used to add
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a local user to a Linux system.
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What it actually does is create an entry
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in /etc/passwd and /etc/shadow.
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When it creates an account for a user,
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it starts with the number 1,000,
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and then it increments for
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each additional user you add to a Linux system.
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We're going to see all of this
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in the demo later in this lesson.
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Now, a quick word about the useradd command.
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It actually takes in
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three files when it creates a user account.
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The /etc/default/useradd file is used to create
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a default user variable setting
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or a set of variables settings.
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The /etc/logins.defs file contains
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information on how to create
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group and home directory creation.
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For instance, it may say to actually create
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a home directory for a user by default or not.
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The /etc/skel is a directory that contains
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default home directory files and
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directories in the home
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directory for each and every user.
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/etc/skel is what's known as a global entry by CompTIA,
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and we'll cover that later in this module as well.
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The groupadd command is used to
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add a group to a Linux system,
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and what it does is create
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an entry in the /etc/group file.
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Let's check out these two commands with some demo time.
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[NOISE] Here we are over in our environment in CentOS,
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and we'll use the useradd command,
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but there are a few options to consider.
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If you're going to create
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a user and you're on a distribution where you don't
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necessarily have it set up to
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automatically add the user's home directory,
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you can use the -m option.
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This will create the home directory in case
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the create_home option is
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not set to yes in /etc/login.defs.
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We'll take a look at that in a moment.
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The other option is that you can actually use g or G to
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specify and add the user to
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an additional group when you create the user.
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Let's take a look at a couple of
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files before we get started.
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Let's take a look, for instance, at /etc/login.defs.
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We'll see if they'll let us in there,
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and it does without having elevated privileges.
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Let's take a look for that create home.
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[NOISE] Then we can
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see here that create home is set to yes.
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Luckily for us on CentOS,
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we don't have to specify the m option when creating
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a user in order to add a home directory for that user.
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Let's also look at the /etc/skel directory.
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[NOISE] We're actually just
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going to do an ls on this, ls -al.
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What we can see in this directory is it's going to
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create three files,
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bash_login, bash_profile,
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and bashrc for each and every user.
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The system uses bash as the default shell.
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You're going to see that those files are
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created when we create a user.
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Let's go ahead and do that.
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Let's create a user called test,
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and we'll add it as a user that has pseudo rights,
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someone that can elevate their privileges.
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What we'll do is we'll do that by saying we want
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to do a useradd.G.
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[NOISE] For the user test,
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we're going to add it to the group wheel.
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In CentOS, the wheel group is what
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controls access to be able to pseudo up.
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It's known as being a part of the pseudoers file.
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We can create the user test here with useradd,
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and then we add it to the group wheel by
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specifying the G option to useradd and we
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have to be elevated
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to root privileges in
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order to run this with the pseudo command.
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Let me type in my password for that.
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There we are, we're good.
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Now let's go ahead and
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take a look and see if we could find
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this user's grep for test in /etc/passwd.
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We can see that the user test is created.
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It has an ID above 1,000.
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One thousand and two means it's probably
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the second user that was
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created on this system behind me.
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That's really all that we need to know about using
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useradd over here in CentOS.
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Let's take a look at this in Ubuntu
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real quick because there's
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a couple of wrinkles over there.
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[NOISE] Here we are in our Ubuntu environment,
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[NOISE] we get logged in.
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We're in our Ubuntu environment here,
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and let's just go ahead and clear the screen.
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[NOISE] cd back, clear the screen.
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Here we are in our Ubuntu environment,
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and what we're going to do
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here is we're just going to run
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useradd test [NOISE] as
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well without any additional options.
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We need to be pseudo to do this, of course.
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Let's do that. Now let's go ahead
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and see if we can find this home directory.
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Let's go to home test
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and there's no such file or directory.
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Let's actually do a [NOISE] less on
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/etc/login.defs and we'll see if we can find
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create_home, and that's not found.
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An Ubuntu system does not have
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>> a user created by default.
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>> Instead, what we need to do is we need to specify,
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we want to create a user home directory
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when we create the user using useradd.
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[NOISE] Let's go ahead and remove the user.
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We're going to jump ahead a little bit and use
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a command called userdel.
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I'll talk about that later in this module.
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But we're just going to go ahead and do userdel
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-r to remove test.
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We need to be pseudo to do that.
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There we go. Let's clear our screen.
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Now what we can do is we can do useradd,
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we'll add pseudo to the front of
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that useradd and we'll do -m
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-G. That will not only
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add the user to a group for pseudo rights,
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it will also create the user home directory.
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On an Ubuntu system, if you want to have pseudo rights,
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instead of using the wheel group you use
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the pseudo group and we'll
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add a user called test2 to this group.
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We'll do pseudo useradd mg
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to the pseudo group test2 and
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>> hit Enter and there we go.
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>> Now we can do a grep for test on /etc/passwd,
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[NOISE] and we can see that test2 has been created with
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the user account ID and group ID of 1,002.
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It's in home test2 with
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the bin shell as its default shell.
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Let's go ahead and see if we can get into home test2.
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[NOISE] We go to
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home test2 and we see that that directory exists,
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and if we do an ls -al,
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we see that it actually has all of
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the bash files that we
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found in the /etc/skel directory as well.
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One last thing, let's go ahead and
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take a look at the groupadd command,
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and the group add command is
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much more basic than the useradd.
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Really, the only thing that we want to do
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with groupadd is maybe
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add a number or a group ID,
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a GID, to a group when we're creating it.
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Let's create a group here and
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>> we'll call the group best,
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>> and we'll give it the group ID 1337.
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We'll say groupadd [NOISE] -g 1337,
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and we'll call the group best.
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[NOISE] We need to be pseudo to do this as well.
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Then what we can do is we can do grep for
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best in the file /etc/group,
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and this is the group file where all the stuff is stored.
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We can see that we have an entry for
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the group best with the group ID of 1337.
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[NOISE] We've reached the end of this lesson,
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and in this lesson, we covered
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user and group creation using
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the commands useradd and groupadd.
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Thanks so much for being here and I look forward
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to seeing you in our next lesson.
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