umask and Permissions
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Video Transcription
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>> Hey, Cybrarians. Welcome back to
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the Linux Plus course here at Cybrary.
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I'm your instructor Rob Gills.
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In today's lesson we're going to be
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discussing the umask and Permissions.
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Upon completion of today's lesson,
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you are going to be able to understand
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the purpose of umask.
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We're going to talk about how umask is configured,
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and then we'll determine where are umask
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should be set to set it permanently.
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In addition to ownership that an object is created
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with it gets certain default octal permissions.
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In Linux, files get the default octal permission 666
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and directories get the default octal permission 777.
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That means read, write, read,
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write, read, write for files for users,
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groups and other,
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and 777 is read,
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write x for everybody.
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But when we made a file in the demo in the last lesson,
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that file that we touch had
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the permission 644 by default.
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Why is that?
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Well, it's because of the user mask or
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umask that is set for this system.
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We can see this if we just type umask on
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the command line, it'll display 0022.
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What that means is that the umask removes or
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subtracts bits from the default Linux permissions.
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That means that it's going to give
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a system default of 644,
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which is read, write and then read,
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read for user group and owner on the files,
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and then directories only the user has read,
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write and execute permissions.
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Everybody else has read and execute permissions.
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Those are effectively the
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default permissions that you get when
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you apply the default octal permissions with the umask.
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How does that get configured?
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Well, there's a couple of different things you can
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do if you want to configure on the fly
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because you're creating a bunch of files and you
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want them to have specific settings,
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you can just do it on the command line.
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Say, for example, if you want a user and
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group owner to have full directory access.
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So u and g both have 775,
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and you want to make sure that any users and
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groups in that directory have read,
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write access to the files.
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So six and six and then four,
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you would do this by changing the
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>> umask from 022 to 002.
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>> We can do this by just changing,
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making the change and then making a directory and
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touching the file and making sure it works properly.
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We could type in umask 002.
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And then when we do make directory
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one and touch file one,
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What that's going to do is we're going to
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see now when we do
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an li/l that the directory has read,
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write execute, read, write, execute, and read,
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execute permissions, which is 775.
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Then if we look at a file that we created,
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we'll see that it has read, write,
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read, write, read permissions, which is 664.
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However, these umask changes that we
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make on the fly on the command line,
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they're are only effective for
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the duration of the session.
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That's useful if you want to create
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specific permissions when you're doing
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a lot of files or directory creations.
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But what if you want to permanently
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change the umask, how do you do that?
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Well, this is actually configured to one
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of those global directory,
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global settings that we talked about
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previously, the /etc/ profile.
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What we do is we set this differently in
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/etc/ profile depending upon user types.
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We'll cover user types later in the course here.
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But specifically in /etc/ profile,
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you'll see the line umask 022.
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So if we wanted to change that to permanently be 002,
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we would just change
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this line here and it would permanently
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change the way that the umask is set going forward.
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But with that, we reached the end of this lesson.
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And in this lesson we covered
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the purpose of the umask in Linux,
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we talked about how the umask
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can be configured on the fly,
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and then where the umask should be
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set to permanently change it.
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Thanks so much for being here and I look
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forward to seeing you in the next lesson.
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