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content/blog/virtualdisks.md

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+---
+title: "Virtual Disks"
+date: 2020-01-06T22:26:58-05:00
+draft: false
+images: []
+---
+
+Have you wanted to [play with ZFS](https://wiki.archlinux.org/index.php/ZFS/Virtual_disks) or any other filesystem without creating a dedicated partition or device? We can do this through virtual disks!
+
+First, we need to create a [sparse file](https://en.wikipedia.org/wiki/Sparse_file) called `scratch.img` with some max capacity. Let's say 2G.
+
+```bash
+truncate -s 2G $HOME/scratch.img
+```
+
+Now the file is only sparse, if your filesystem supports it. To see, run `du -sh $HOME/scratch.img`. If it says that the size is `0` then your filesystem supports sparse files. Otherwise it does not.
+
+Then, we can format the file with any filesystem we will like. One popular tool is `mkfs` which depending on your operating system can support [`bfs`](https://en.wikipedia.org/wiki/Be_File_System), [`cramfs`](https://en.wikipedia.org/wiki/Cramfs), [`ext2`](https://en.wikipedia.org/wiki/Ext2), [`ext3`](https://en.wikipedia.org/wiki/Ext3), [`ext4`](https://en.wikipedia.org/wiki/Ext4), [`fat`](https://en.wikipedia.org/wiki/File_Allocation_Table), [`minix`](https://en.wikipedia.org/wiki/MINIX_file_system), `msdos`, [`ntfs`](https://en.wikipedia.org/wiki/NTFS), [`vfat`](https://en.wikipedia.org/wiki/File_Allocation_Table#VFAT), [`reiserfs`](https://en.wikipedia.org/wiki/ReiserFS), etc.
+
+To format with `ext4`,
+
+```bash
+mkfs -t ext4 $HOME/scratch.img
+```
+
+Then we can create the mount-point `/mnt/scratch` and mount `scratch.img` to it.
+
+```bash
+sudo mkdir /mnt/scratch
+sudo mount -t auto -o loop $HOME/scratch.img /mnt/scratch
+```
+
+With this, we now have a mounted `ext4` filesystem on `/mnt/scratch`. `cd` into it and have a blast!
+
+## Resizing the Virtual Disk
+
+To resize the virtual disk, we will first need to unmount the virtual disk so we don't create inconsistencies.
+
+```bash
+sudo umount /mnt/scratch
+```
+
+Now we can extend or shrink the drive with `truncate`.
+
+Extend by 1G: `truncate -s +1G $HOME/scratch.img`
+
+Shrink by 1G: `truncate -s -1G $HOME/scratch.img`
+
+Check the filesystem to make sure that no inconsistencies occured. With `ext(2/3/4)` we can do this with the `e2fsck` command.
+
+```bash
+e2fsck $HOME/scratch.img
+```
+
+Then we need to tell the filesystem to resize itself. For `ext(2/3/4)` you can do this with the `resize2fs` command.
+
+```bash
+resize2fs $HOME/scratch.img
+```
+
+Now the virtual disk is successfully resized! We can mount it back with the previous mount command.
+
+```bash
+sudo mount -t auto -o loop $HOME/scratch.img /mnt/scratch
+```
+
+## Removing the Virtual Disk
+
+To remove the virtual disk, we first need to unmount the virtual drive
+
+```bash
+sudo umount /mnt/scratch
+```
+
+Then we can remove the mount-point and file.
+
+```bash
+sudo rm -r /mnt/scratch
+rm $HOME/scratch.img
+```
+
+## Conclusion
+
+With virtual disks we can experiment with different types of filesystems and perhaps try out snapshotting in supported filesystems. If we create virtual disks on [`tmpfs` ](/blog/lxdtmpfs/), then we can have a super fast file system as well!