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I'm thinking of dualbooting Windows 10 and Ubuntu in different partitions of the same SSD. If codes like rm -rf somehow happens in the Ubuntu partition, does this affect Windows, or does it leave other partitions alone? And if it DOES affect the Windows partition, how can I prevent this from happening?

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    Take backups (which you should be doing anyway!) – pjc50 Apr 10 at 10:01
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    Everybody is worried about this, but I suggest you spin up a Docker container and try it out. Most Linux distros will make you answer yes and enter a password to do something truly dumb – bremen_matt Apr 10 at 19:59
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If you have physical access to a computer, you have the power to do anything with the files on it, including reading, corrupting or deleting them.

It's possible to make it harder to accidentally delete files, though.

If you want to read documents on your Windows 10 partition, you could mount the partition in read-only mode. You won't be able to edit Word documents, but it should be enough if you want to read PDF, listen to MP3's or watch movies on your Windows partition. Another possibility would be to create a FAT32 D: partition under Windows, which you would mount with write permissions under Ubuntu.

I could think of at least 5 short commands to destroy a Windows Partition from a Linux system, but they would all require root privileges. Be careful whenever you want to run a command starting with sudo or when a program tells you that "Authentication is required to run".

Finally, be very careful when installing Ubuntu along Windows. The installer makes it clear which partitions are resized, created or deleted but it's still possible to delete existing partitions if you ignore the warnings long enough.

To be safe, please follow @Emmet's excellent advice (be sure to backup your data).

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    There is an equal amount of Windows commands that can damage an Ubuntu partition. – Brilsmurfffje Apr 10 at 10:59
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    @Brilsmurfffje: Sure, it's possible to damage an Ubuntu partition from Windows. Still, Ubuntu is usually installed after Windows, it's easier to mount NTFS in Ubuntu than Ext4 in Windows and command lines are more prevalent in Ubuntu than in Windows. – Eric Duminil Apr 10 at 11:30
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    Whenever I've dual-booted Win/Lin, I would create a FAT32 partition that appears as D: in Windows, and use it to pass anything between the OSes. I simply do not trust Windows accessing ext3/4 or Linux accessing NTFS, with write privileges. – Monty Harder Apr 10 at 20:32
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    If you have physical access to a computer, you have the power to do anything with the files on it, including reading, corrupting or deleting them." I feel like you threw in "reading" a bit too quickly, considering encryption is a thing... – Mehrdad Apr 11 at 2:52
  • @Mehrdad: You're right. I couldn't find a way to mention encrypted files in this sentence, because you can corrupt or delete them even if you cannot decrypt the content. – Eric Duminil Apr 11 at 13:45
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The common basic to prevent data-loss: REMEMBER TO ALWAYS TAKE BACKUP OF YOUR FILES

It doesn't affect the windows partition, because you're running it from your Ubuntu machine.

Picture it like this

/dev/sda1 ntfs-bootfile
/dev/sda2 ntfs-win
/dev/sda5 ext4-root --> (YOUR LOCATION NOW)
/dev/sda6 ext4-swap

If you run rm -rf within your location, it would affect sda5 partition—in which your Ubuntu system reside. So it only affect Ubuntu.

Supposing you have grub boot loader to load the 2 OS (Ubuntu and Windows), if you accidentally remove GRUB file aswell, Windows would not be able to boot, but the data inside will remain intact.

However, Ubuntu tend to mount Windows partition when it available, and if you say ran rm -rf /*, Ubuntu—without hesitate will delete ALL file, this include Windows partition.

There's also infamous dd command, hence the disk destroyer nickname. This is widely used to: formatting drive, cloning disk, creating bootable usb etc.

dd has ability to dump entire main drive, dd if=/dev/zero of=/dev/sda would replacing all data on main drive with zero—and goodbye to our data !

With that being said, please be very careful when running command and always take a second look before doing execute something—it's best to prevent disaster before it happens.

I highly recommend you to learn various Linux command, this way you could tell what does the command do before you ran it.

Also, again please be elaborate when working with dd, it's common mistake to mistype sdb to sda, anything happens after that is horrible.

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    The OP asks about "codes like rm -rf." To me, this means the various destructive commands that can be done on a Linux system. Some of these will cause problems on Windows. For example cat /dev/zero > /dev/sda will write zeroes to all of /dev/sda, thus deleting all data on that drive and possibly the entire computer. Of course, such things are less likely in practice but they need to be acknowledged for a complete answer. If truly secure isolation is needed to prevent Linux from causing problems on Windows (or visa-versa), the only sufficient method is a virtual machine of some sort. – john01dav Apr 10 at 5:42
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    Also, the windows partition could be mounted in /media or /mnt. In that case, rm -rf would surely be able to destroy windows files. – Eric Duminil Apr 10 at 8:40
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    This answer is incorrect if the Windows partition is mounted in Ubuntu! If, say, the Windows filesystem is mounted under /mnt, and you run rm -rf /*, it's bye bye Windows files... – marcelm Apr 10 at 8:41
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    @wizzwizz4 "No, they'll be deleted afterwards". It depends on how the "*" expands, usually in alphabetic order, so "/bin" before "/mnt". But in fact, the order does not matter, because, as you already said, "rm" already resides in memory, and this is the only thing that matters. – rexkogitans Apr 10 at 10:33
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    @EricDuminil Assuming that the system isn't swapping, as soon as rm opens all the libraries it needs, it will not matter if those libraries are deleted from the file system. They will stay on disk, unlinked but still open by rm. What will likely cause a problem is when the OS tries to fire up a new process that needs a file or device that has already been deleted. You might panic the system at that point. – doneal24 Apr 10 at 16:47
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If the fact that you can't keep two operating systems on one disk from harming one another makes you look for other solutions, here more options. They depend on your practical needs and your budget.

You can run one (or both) systems as virtual machines instead of using separate partitions. The virtual machine should have limited access to the host or other virtual machine, so you cannot accidentally damage the host machine (though there will still be deliberate ways). Another advantage is that you can use both at the same time.

If you want your two operating systems completely separate, put them on swappable hard disks or even better, separate computers (less chance to accidentally destroy your disks).

If you need to be able to access the data but very often do the kind of stuff on your Linux which can harm the Windows system accidentally with a small lapse, put them on different machines and access Windows only through a remote access tool which respects the Windows security mechanisms. You'll get full access to your data and very high security at the price of a few hundred Euro/USD for extra hardware. Additionally, you have a backup system if one fails, so if you work on these machines, the extra cost can pay off.

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Risks like this can be easily mitigated by enabling BitLocker drive encryption on the Windows10 operating system. Encrypting the partition makes it for Ubuntu unable to mount and thus perform actions like rm -r

It also means that you are unable to share files with the ubuntu system via the windows partition.

If you would like to share data between the two operating systems I would advise you to create a separate data partition which you mount on both operating systems.

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    Being unable to mount a file system does not make Ubuntu unable to damage it. dd could still overwrite relevant sectors of the disk used by windows, making the encrypted file system permanently unrecoverable. – Patrick Trentin Apr 10 at 10:56
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    @PatrickTrentin: Indeed. You may not be able to read any meaningful content from Windows partition, but cat, dd, fdisk, parted, or mkfs.ntfs will all happily destroy any data on the partition, encrypted or not. – Eric Duminil Apr 10 at 11:36
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Grub keeps on System. Before doing it you have to be familier with diskpart and Grub. Verify no'one tells you here, that your PC is on the list for Linux. Mine was not;)

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