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Next lesson we have is about system maintenance

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commands. Maintenance commands are those that are

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used by system administrator to reboot the system,

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shut it down, or bringing it in single mode, or

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whatever the tasks they have to perform while

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other system other users are logged in, or have

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them log off, and then bring it to the single user

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mode. The commands that are used to bring down a

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Linux system is shutdown, init. Now init has a

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different level of bringing the system down or

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rebooting. It goes anywhere from 0 to 7. 0 for

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simply shut down, and six is to reboot, and three

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is to bring it in in multiuser mode, and there are

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many other options. Then we have a reboot command.

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As it read, reboot is simply to reboot your Linux

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machine. And then we have halt command. halt shuts

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down the computer. And if there are any processes

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that are running, that needs some time to bring

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down the process, halt doesn't care, it just shuts

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down right away. It is as if you are pressing the

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button on your physical system, the power button,

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and holding it in, powering it down. It's just like

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that. So now let's get into our Linux lab server,

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and we will try out few of these commands. I will

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log into the Linux machine by logging into the PuTTY.

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I'll open it up.

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[No audio]

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Log in myself.

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And of course who we are? We are self. Which directory we

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are in, and which hosts are we on, because every

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time you are ready to reboot a machine, this is

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definitely a command you need to run, which is

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hostname, to make sure which computer you are on or

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which Linux machine you are on. So anyway, let's

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clear the screen. And the first command is

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shutdown. Of course, I don't want to shutdown

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this machine right now because we're going through

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the training. So I'll just quickly go through this

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man page of shutdown. And you will see it tells

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you shutdown, halt, power-off, or reboot the machine.

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shutdown has different options if you want to use

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these different options with it. And those options

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are listed as you go down. If you type shutdown

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-H, it will do exactly the same as

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if you would just type halt, and P for power off,

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r for reboot, h for equivalent to power off, unless

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halt is specified. So you could view every single

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options that is available with shutdown. Then we

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have the next one is init.

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init is a systemd service.

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There are different options associated

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with init, sorry with, guess with init, and those

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options, you can view them one by one. As I said,

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there are options zero to seven, you can view

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those options and see what exactly they do. Then

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we have reboot. reboot simply reboots your

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computer, shuts it down, and power off, and bring it back online.

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And the last one you have halt.

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poweroff, reboot, halt, poweroff. So pretty much all

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these commands. You could use any one of these

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commands except the reboot command and init command. So

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let's say, now we want to reboot our machine. In

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order to reboot your machine, you have to be root.

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[No audio]

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So become root. And if I do reboot,

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hit enter. And

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you will see I have lost my PuTTY session. And if

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you are logged into your console, you'll see the

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system message is coming up, this system is going

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down. So we'll give it some time. I will fast

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forward from here.

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Okay, so now I got the prompt

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back, the system has been rebooted, I've logged back in.

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Now your PuTTY terminal will continue to try

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to connect to your system. If it's shut down, it

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tries to connect it every second or every five

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seconds depending on the setting that you have

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specified, and your PuTTY options. So anyway, this

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is sweet and simple and straightforward lesson

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that we learned about four commands. Try them out

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and get familiar with it.

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