Transfer Commands (Demo)
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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
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to discuss transfer commands.
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Now upon completion of the lesson today,
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you're going to be able to determine when to use
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a transfer command, versus just
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using a regular file or directory option.
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We're going to use the scp, and rsync commands.
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When you're looking to move a file or
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directory for one computer,
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like one Linux system to another Linux system,
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you're going to need to use a transfer command.
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But if you're just moving a file around
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a specific Linux system in
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the same file system, or in the same Linux system,
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you're going to use an operation such as
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a copy, or move operation command to do that.
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The transfer commands that are covered on the Linux
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plus exam are scp and rsync.
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Let's check out these two with some demo time.
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[NOISE] Here we are over in our CentOS environment,
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and the first command
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>> we're going to look at over here is
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>> the secure copy command, or scp for short.
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Scp is just a feature of the SSH protocol suites,
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so we have to install anything out of the ordinary.
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SSH is on your Linux machine, great.
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You've already got a secure copy, you're good to go.
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Now, scp is used to copy
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small files from one machine to another.
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For larger files or directories,
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we're going to want to use something like rsync,
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and we'll talk about that next.
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The scp command itself is pretty basic.
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We'll use it here to copy a file from CentOS to Ubuntu.
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The syntax is just going to be scp,
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[NOISE] and then the file that you want to
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copy, and the remote server you want to copy to,
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and then the path and the remote server where you're
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going to place the file that you're copying.
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For rsync, let's
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go to my home directory,
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>> and I think we're actually there.
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>> Let's do a PWD, and we're in my home directory.
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Let's just grab the Alpha source file
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again, and we'll copy it over to Ubuntu.
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Now on this system, let's just display as the host.
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I've actually just added an entry here for Ubuntu.
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That's a shortcut, so I don't actually need
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to know the IP address for it.
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I've set that same thing up on
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the Ubuntu systems, so that we can go back and forth.
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It already knows the location and
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the IP addressable systems because it's an empty host.
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That's a nice shortcut in case
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>> you ever need to use that.
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>> We'll just refer to the Ubuntu system as Ubuntu,
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even though it's actually called Ubuntu 20,
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because that's the name that
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>> I gave it in the host file.
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>> If we go on SSH to Ubuntu over here,
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we're going to land in my home directory.
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That's because we're SSH into Ubuntu
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from my user, from Rob.
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If we do a present working directory,
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we see LS home Rob, and if you look in here,
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we see a bunch of files, but we don't see
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here is Alpha sort. Let's go back.
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Remember we're going to grab the Alpha sort
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file, and it's in this directory already,
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so you don't need to specify the entire path,
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we can just say we want to copy over Alpha sort,
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and we're going to send that over to Ubuntu,
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and we're going to put it in home Rob.
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Now when we hit "Enter" it's copied over,
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we can see it 100 percent of it's copied over,
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it copied over about 81 bytes.
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It copied over at a speed of 8.8 kilobytes per second,
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and it took less than a second.
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Pretty small file, so that was nearly instantaneous.
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We can do an SSH into Ubuntu.
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Now when we go in here, again,
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we're in my home directory, and we see that
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Alpha sort file has been copied over.
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The nice thing about SCP is
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that we can go in the opposite direction.
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We can connect to another server and copy
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a file to S. For instance,
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here we could do an SCP,
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we can specify the remote server that we want to
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copy from, the path where the file that we
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want to copy lives on the remote server, and then the
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local file location we want to copy to on this system.
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Let's take a look here.
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We have a file in here called Ubuntu file.
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Let's do a cat on Ubuntu file in this system.
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I'll just clear the screen here.
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We can see that this file says, "Hi,
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I'm from Ubuntu 20". Let's get out of here.
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I'm just hitting "Control D" to
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exit out, and go back to CentOS.
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If I do an LS here,
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you can see that we don't have Ubuntu file.
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It's not on the system yet.
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Nothing up my sleeves.
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No tricks here. What we'll do is we'll copy
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that file from the Ubuntu machine, to this system.
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We can do an SCP from Ubuntu in
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the home Rob directory
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of the file that we called Ubuntu file,
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and we're just going to put it here.
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Now, that is just a shortcut to say here, or it
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just means put the file in this directory.
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When you hit "Enter" that's copy done,
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again, we can see 100 percent is copy done.
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It's about 25 bytes.
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It was 21 kilobytes per second,
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and it took zero seconds to copy.
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You do an LS and now we see the Ubuntu file.
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Just to verify that we didn't do
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>> any merge for anything,
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>> we do a cut, and we see that has the same contents
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of the file that we just looked at on our
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>> Ubuntu system.
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>> The only other option that we really
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need to know about SCP is that we
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can't copy directories, unless we use an r option.
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R option is the recursive option.
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Use the copy of directory.
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If we try to copy without it,
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it'll give us an error message.
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For instance, if we're still here in home Rob,
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and if you recall, we have this subdirectory
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>> right here.
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>> If we want to copy subdirectory over to
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Ubuntu, and then put it into my home directory,
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it's going to give us an error message.
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It's going to say that SCP,
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we can't copy this over,
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some directory is not a regular file and they're right,
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it's not a regular file, it's a directory.
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We have to use the -r option to
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recursively copy that file. Let's try that.
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You know what, we're getting a permission denied issue
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here, because there is no home directory.
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That's a typo on my part.
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You do scp -r somedir
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Ubuntu home Rob and hit "Enter", and there we go.
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It's created that honest for us on the Ubuntu system.
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Now if we were to go an SSH back into Ubuntu,
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and then just do an LS,
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we're going to see that we also have
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some directory here as well.
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Now the next command we want to talk
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about is the rsync command.
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Rsync is used to remote sync or
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copy a file or directory between servers.
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The power of rsync is that it can just copy
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changes that have happened
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since last time the command is run.
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It copies just the changes between files,
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>> and directories,
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>> keeping both copies in sync, hence rsync.
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At heart, the rsync command can be run
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basically just like RCP or SCP.
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For instance, if we wanted to do an rsync with
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a directory that's here on
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Ubuntu back to CentOS, we can do that.
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We deal with basically the exact same syntax.
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If we look right here, we see we have
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the Ubuntu directory. Let's clear our screen.
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Let's do an LS, so we have
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>> a little bit more real estate
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>> to work with and to do
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a copy or a sync of that back to the CentOS system,
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we do rsync -r and we specify that we want
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to grab ubuntuDir in the system.
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We're going to copy that to CentOS.
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We're going to put that in the home rob directory.
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Then I'm going to need to type in
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the passphrase for my SSH key here.
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But that's done.
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Now if we go back to CentOS
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here and we do an LS in CentOS,
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we can see that we have the Ubuntu directory right
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here as well as the Ubuntu file.
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The other thing that we should know though,
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is that our sync is
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really like infinitely more powerful than SCP.
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Let's go back to Ubuntu real quick.
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As you're over here in CentOS,
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let's just do an LS -al on ubuntuDir.
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What we can see is that that file was created today,
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April 24th, 23,
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24, and we see that the contents of
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the directory you don't want is
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this first subdirectory in that file.
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Let's go back to Ubuntu.
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Then we'll do an ls -al on ubuntuDir here.
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We can see that that was actually
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created on December 7th.
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We didn't preserve the timestamps
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when we needed the rsync.
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Well, we can preserve timestamps
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with rsync just like we would with
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a regular copy by using the a for archive option.
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Let's actually just use a little short one-liner here,
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we're going to go to CentOS and we're going to remove
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the directory home rob ubuntuDir.
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That's going to remove that from the CentOS system,
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not from this system, but from CentOS,
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and that's one of the nice things about SSH.
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You can actually pass in
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just a little one-liner bash commands
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right through SSH without
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actually having SSH to a server.
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Then it just returns you to
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the shell on the server that you're in it from.
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Super-helpful. We've removed that.
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Now if we run the rsync command
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again that we ran previously,
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and I'm just going to hit the up arrow until
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we get back to it.
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I'm going to actually add the a
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for archive option to the front of this,
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and we'll move this file back over to CentOS.
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I'll type in my SSH key again.
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Now if we just exit out of here and go
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back to our CentOS system.
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Now I do an ls -al ubuntuDir,
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we can see that it has the timestamp preserve,
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December 7th at 21:55,
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just like here, December 7th at 21:55.
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Now another really powerful combination
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with rsync is azvh.
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That's SSH back to Ubuntu.
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Actually, before we do that,
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let's just go ahead and remove ubuntuDir from here.
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Dir -r, remove that thing from there,
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SSH back to Ubuntu.
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What we're going to do now instead of
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just doing an rsync ar,
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we're going to do an rsync azvh.
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I'll tell you the reason for this.
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A for archive, that's going to transfer,
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is going to preserve all the permissions,
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all the timestamps, everything we just saw.
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Z is going to copy it,
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and it's going to copy it compressed
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so that it takes less time to copy.
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The v option displays output,
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it shows you all of the files that
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>> are being transferred.
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>> Then the h output gives you
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>> a nice human-readable output,
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>> especially like at the bottom,
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it gives you a little result.
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We remove the Ubuntu directory on CentOS.
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Let's run this again from
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here and move it back to CentOS.
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We'll type in my SSH key password again in the system.
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Now we can see that it
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tells us what it's actually doing,
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it's sending an incremental file list.
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Here's the file that's moving.
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It's going to move the Ubuntu directory.
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It's going to move the subdirectory dir 1,
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the subdirectory dir 2,
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the subdirectory dir 3.
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It's on 145 bytes received 32 bytes
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and took less than a second,
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instantaneous because there's nothing
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in these files. They're all just for example.
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That's pretty much all we really
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need to know about rsync.
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Rsync is super-helpful.
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It has a lot of great options,
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so definitely invest more time and trying
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other options if you have a machine to play on.
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But for the purposes of the Linux plus exam,
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that's really all we need to know about SCP and rsync.
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With that, we reach the end of this lesson.
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In this lesson,
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we covered performing file
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and directory transfer operations
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with SCP and rsync.
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Thank you so much for being here and I look
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forward to seeing you in our next lesson.
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