Tag: power management

Short: The Halt Command

Today’s article is intentionally short because we’re simply going to learn about the basics of the halt command. There won’t be much to this article, because there doesn’t need to be.

If you have a Linux system, you can access the halt command. The halt command is one of the commands used for power management but not one you’re likely to use. You’re more likely to run reboot or shutdown command.

Why the halt command? Well, it’s archaic these days. I really can’t think of all that many, or any really, reasons to use it. I’m told you can use this command for low-level maintenance but I’ve never been able to use that for anything.

The Halt Command:

Under the hood, when you issue the halt command, the operating system goes through a series of steps to ensure a clean shutdown. It stops all running processes, unmounts filesystems, and sends signals to devices and services to shut down gracefully. Once everything is properly shut down, it halts the CPU and powers off the system hardware.

If you check the man page (with man halt) you’ll see that it agrees with the above statement and is a tool for managing your power state.

halt, poweroff, reboot – Halt, power-off or reboot the machine

While there’s more to the command, we’ll just cover the basics. So, press CTRL + ALT + T and open your default terminal emulator.

Or not… You only want to run the halt command when you need the command. It will shut everything down and that’s not something you necessarily want to do while reading this article.

The syntax is quite simple:

This will halt all the processes and leave the computer running. To completely turn it off, you’ll need to use the power button.

You can also try this command:

Now the -p is handy. After halting the computer, it will initiate a shutdown.

Then, you might find this a bit handier…

If it’s not obvious, the --reboot flag will reboot the computer. This means you needn’t use the power button for anything. It should just halt the system and then initiate a reboot sequence.

Closure:

That’s all there is today. I told you, it’s a short article. We just covered the halt command and nothing more. This isn’t complicated enough for a full-length article but is still a command that deserves to be mentioned. So, it has been mentioned. The good news is that there might be a future article that refers to this article, so my time might not be wasted.

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A Quick Look At The Shutdown Command

This is going to be just a quick article about a command many of you will be familiar with, as we take a quick look at the shutdown command. This is pretty basic and something everyone should be familiar with.

Our pure-GUI users will just shut the computer down with the menu option but sometimes a GUI is unresponsive. There are other times when you don’t have GUI access, as there’s no desktop environment loaded. When this happens, you can still shut the computer down. To do this, you can use the shutdown command.

There’s not a lot to the shutdown command, but the good news is that you won’t have to install anything to use it. If you’ve got a Linux system, you’ve got access to the shutdown command.

In fact…

shutdown:

As I said, you won’t need to install anything to use the shutdown command. It’s something that’s built in. You can check the man page with the following terminal prompt:

If you run that command, you’ll see that this is the correct tool for the job. It will in fact shut down the computer, though it has a few options that we’ll cover. We won’t cover everything,  just the things you’re likely to need.

The man page describes the command like so:

shutdown – Halt, power-off or reboot the machine

See? If you want to shut the computer down (including halt and reboot) then this is the correct command for the job.

The Shutdown Command:

As mentioned above, this is a terminal-based command. That means you’re going to need an open terminal. If you press CTRL + ALT + T a terminal should pop up. If not, there’s a terminal in your application menu.

Some systems may require ‘sudo‘ for this. This is not true for all distros and you’ll need to discover that on your own. I’ll omit the sudo in this article.

The basic syntax is this:

That command will stop anyone from logging in and shut the computer down in five minutes. It’s the basic usage of the shutdown command.

If you want to shut down the computer immediately, try this command:

If you want to reboot, try this command:

Again, that will reboot the computer in five minutes and stop anyone from logging into the system. 

If you want to reboot immediately, add ‘now’ to the command like so:

You can also halt the system. If you halt the system, it will remain powered on but all CPU functions will cease immediately. That works just like the above commands. To halt the system in five minutes run this command:

If you want to halt the system immediately, run this command:

You’ll need to power the system down and back on with the power button.

You can also schedule a shutdown, reboot, or halt. To do that, you use the HH:MM (hours/minutes in 24-hour time), like so:

If you schedule a shutdown, nobody will be able to log in within five minutes of the scheduled shutdown command. You’ll remain logged in and people can log in until that time is reached, but after that time is reached no new users can log into the system.

There is more to the shutdown command but that’s all you’ll realistically need, even as a system administrator. And, if you don’t know this already, you’re a system administrator even if you’re just a basic Linux desktop user. You’re in control of your computer.

Closure:

I thought I’d cover the shutdown command because it’s something I haven’t covered yet. I started off trying to cover the basics first, but I didn’t cover everything. There are still basic functions that I’ve yet to cover. I’ll get to them eventually.

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Let’s Reboot Your Linux Computer

Today is another article with one of those things you probably already know, it’s about how you can reboot your Linux computer. Specifically, we’re going to reboot from the terminal. You can use the GUI to reboot easily enough, but if that’s frozen and you don’t really want to do a hard restart, you might as well reboot it if you can.

If you can’t reboot your computer because it appears frozen, consider the Magic SysReq Keys. (More specifically, the REISUB method.)

If you aren’t already aware, there are all sorts of ways to reboot your Linux computer. Like oh so many things in Linux, there’s a multitude of ways. We’re just going to cover a few of them, because you really don’t need to know more. Well, if you do need to know more,  you probably already know those ways to reboot your Linux computer!

It’s also another fairly simple article. That’s good (for me) as it’s a bit like work lately and I don’t want the site to really be about work but rather being about a hobby. If it’s work, I wanna get paid… 

This is also useful information if you’re working on something remote. You don’t want to shut that system down and have to have someone go physically turn it back on, so you reboot the system – making sure to reboot the right system and not the system you’re physically using. I’ve done that more times than I care to share – and I’ve done the reverse as well. It’s seldom good if you enter the reboot command and immediately follow it with a verbal, “Oops.”

Reboot Your Linux Computer:

This article requires an open terminal, because we’ll be learning how to reboot your Linux computer from said terminal. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

With your terminal now open, let’s start with the easiest of the commands to reboot your Linux computer:

With some distros, that’ll be all you need. With others, you may need to have elevated permissions. This is also often true if you’re connected remotely, via SSH. So, in those instances, you’ll need to preface it with sudo and use your password when asked. Like so:

If you want,  you can also use the shutdown command. That’s pretty easy, you can just use:

The -r flag tells the system to reboot and the ‘now‘ means to do so right now – immediately. You can play around with that ‘now’ bit, like so:

Instead of ‘now‘ you’ll see there’s a ‘1‘ and that’s how many minutes you want to wait before rebooting the system. You can change that to any number you’d like, I suppose.

Finally, you can use systemd to reboot. Why? Because of course you can! It’s systemd, and you can do anything with it! (Kinda like zombo.com, I guess.)

That’ll happily reboot your Linux computer, all nice and neat and proper. It does exactly what you’d expect it to do, so there’s that.

Closure:

There you have it. You now have a few ways to reboot your Linux computer from the terminal. There are other ways, including init or whatnot. You can also just use the GUI if you’re working locally. It’s Linux. There are all sorts of ways to accomplish a given task. That’s a good thing.

I find myself rebooting from the terminal more often than not, simply because I’ve already got a terminal open and it’s just as quick for me to type the reboot command as it is for me to go clicking around. I’m also often testing other systems and really don’t want to have to go fishing around to find the command, then click on some sort of secondary agree menu or the likes.

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Let’s Learn About Halt

Today’s article is about the halt command. The reason we’re writing about the halt command today is because I was halfway through another article before I realized I’d already written an article on that subject. So, this is going to just be a nice, easy article.

And, yes, yes I did write more than half of an article that I’ve already written. I ain’t even intoxicated!

The command we’re looking at using today is called ‘halt’. For such a little command, here’s an interesting post about the difference between halt and shutdown. And, if that’s not enough, you can read the other answers and comments on that page. 

Anyhow, halt is described like this in the man page:

halt, poweroff, reboot – Halt, power-off or reboot the machine

Of those three, we’ll just be covering the halt. Yes, the man page contains all three in just one page. They’re all related. As I said, we’ll just be covering the useful features of halt command today.

And, without further ado…

The Halt Command:

This article requires an open terminal, like many other articles on this site. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

Once you have the terminal open, the first use of halt would be just to halt the system:

That will halt your CPU. It probably won’t shutdown your computer all the way, it will just stop it. So too won’t the -f (force) flag. If you force it, it just stops the CPU. It looks like and requires sudo:

Finally, of the options we’ll cover, is the -p flag, and the -p stands for poweroff. It’s just another way to shut down your computer, and it obviously looks like this:

Those are about the only ways you’re ever going to use it, if you use it at all. It’s not a command that you’re likely to bump into but now you know it exists and how to use it.

Closure:

There you have it, another article. This one covers the halt command in Linux. It’s not a major article, but I needed one in a hurry – just to ensure there’s one scheduled. While my health is mostly returned, I’m still not so caught up that I have a bunch of extra articles. Feel free to step up and write one or two!

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How To: Shutdown Linux From The Terminal

Today’s article is going to tell you how to shutdown from the terminal. I’ve previously explained how to reboot a ‘frozen’ Linux system using the Magic SysReq keys. Today, we’ll shutdown from the terminal. It’s a quick and easy article – as the holidays are eating a bit of my “free” time.

Why would you want to do this? Well, if your Linux system isn’t quite frozen or your desktop GUI isn’t something you can reach, then you may want to press something like CTRL + ALT + F3. That should crack open a TTY where you can login and issue commands to your system. Maybe you’re working on a server and need to shut it down? Who knows, but the command is there and it’s a useful command to keep in mind.

For this article, we’ll mostly be using the shutdown command, and the man page defines it as:

shutdown – Halt, power-off or reboot the machine

And it does pretty much what you’d expect from such a command. However, it’s not just a basic command, there are flags and some options that go along with it. So, we might as well take the time to learn about it. After all, you never know when you want to shutdown Linux from the terminal.

Shutdown Linux From The Terminal:

Like oh so many articles, this one will require an open terminal. If you’re connected to a remote server via SSH, you already have a terminal to work with. If not, just press CTRL + ALT + T and your default terminal should open.

Once you’re ready to shutdown your Linux system, you can enter the following to shutdown immediately:

Obviously, that command will shutdown the system immediately, so don’t practice it unless you plan on shutting down – ’cause you will. You can even shutdown at a specific time by using this format (and 24h time):

You can also use the +MM function. To shutdown in 10 minutes, you’d use a command like this:

If you change that +10 to +0, it will also shutdown immediately. If you have users of the system who should be notified of an impending shutdown, then you can actually send them a message. That would look like:

So, what happens if you schedule a shutdown and need to stop it for some reason? Fortunately, the shutdown command will let you cancel an impending shutdown – so long as you get there in time. That’s done with the -c flag, of course.

If your cancellation will impact the users, you can even include a message in that. It’s done like this:

And that’s about it, really. There’s a bit more to the shutdown command, but it’s mostly going to be used in one of the ways mentioned in this article. If you want more information about the shutdown command, simply run man shutdown and read the help file.

Closure:

And there’s another article. This one will tell you how to shutdown Linux from the terminal, a handy skill to have as a user or as an admin. It may seem like a pretty basic command, but that doesn’t mean it can’t be included on the site. 

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your own site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

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