![]() That's where dd really shines, having a full bare metal image of a system. And that way, if anything goes wrong, cause I've had SD cards die left, and right, all I have to do is get a new SD card, restore that backup, and then off I go, I've got a whole image. I have a little raspberry pi server at home that runs Ubuntu and I have a cron job that runs every night that takes an image of the SD card, the whole SD card, and drops it off on another server. I'll give you an example of how I use it. It could take an image file and convert it into a physical disk and back and forth. And that's why we had the dd tool, but copy and convert meant it could copy a disk and convert it into a different format, either dropping it onto another live disk, or dropping it as an image file, converting the contents and then vice versa. And so they just bumped up a letter in the alphabet to dd. It actually stands for copy and convert, which is weird, but they couldn't name the tool cc because that was already used by the C compiler. But the name of the tool, it doesn't actually stand for anything that starts with d's. ![]() Or some people say it stands for disk destroyer, because if you get the command line wrong, you can wipe your entire disk, lot of fun. If you go on the internet and search, you'll find tons of people that say, yeah, dd stands for disk duplicator. In fact, most people assume dd stands for disk duplicator. So you need to think about it in terms of disk. If you're looking to back up just a folder or synchronize a folder between one system and another, dd is not really good for you. But the thing about dd that sets it apart is it's really designed to work with entire disks. And there's a number of times where it is not, it is a venerable old tool that's included in every Linux distro that I'm aware of. But how do we know if dd is the right tool for the job, Don? - So there's a number of times where dd is perfect. And then lastly, we're going to see how to restore a disk, all using dd. And we'll see a lot of options that we can provide to change the way that backup behavior performs. We'll see how to use it to back up an entire disk. In this episode, we're going to learn about how it differentiates itself from, like, tar and rsync. We've talked about a few backup tools, the logical next one is dd. So, so now we're looking at backing up with dd. I am Zach and this is Don, our Linux maestro. Of course, the only thing this command will do is load the processor for a few seconds.- Do you want to back up an entire disk, or maybe clone one disk to another? Well, join us. Giving this command a sense load, it turns out that the system will generate 500 megabytes of random values and write them into a null device. Thus, the described command reads 5 * 100 megabytes from the / dev / urandom device to the / dev / null device. count: just the number that indicates: how many pieces will be copied.You can think of this argument as the size of the piece of data that will be written or read, and the number of pieces is regulated by the next parameter. bs: the number of bytes to be written at a time.The same thing, we can write both in a regular file and directly in the device. Specifies a file that can be either a regular file or a device file. ![]() # dd if =/dev/urandom of =/dev/null bs = 100M count = 5 ![]() I will start with a small example that clearly illustrates the main parameters of the command: restore data from a backup on media and moreĪnd, when combining the capabilities of dd and supporting the cryptographic algorithms of the Linux kernel, you can even create encrypted files that contain whole files yy system.Īgain, in the note I will describe the most frequently used examples of using the command, which greatly facilitate the work on UNIX systems.Creating a disk image using dd command:Īt first glance, nothing outstanding, but if you consider all the features of this universal tool, you will understand why it’s important to learn about Linux dd command, with the dd command you can perform quite complex operations without involving additional software, for example:.
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