I’ve been using virtual machines since I’m in high school. I thought it’s cool then, and still now. I’m just an ordinary student and use computers to do daily tasks, and some programming and some funny things. But virtual machine can still make my(and our) life much easier and funny! Here are my funny experience of using virtual machines, and you may also want a try =)

I wanted to write this long ago, so some of the cases described happened more than two years ago, so I can’t remember clearly what happened, and I’m not able to find enough pictures of years ago. Sorry for that.

The title sounds big but this post is not technical and I’m just going to talk about how to use virtual machine for daily use, not for study the machines themselves. I’m just a silly user and don’t know the things behind these machines.

Virtual machine is really a bless.

1. Be a normal user - use VM to run another OS

Wanna have a taste of Linux on you Windows laptop? Can’t use a software because you are using Mac? Just use a virtual machine. There is not much to talk here.

2. WSL is not enough!

Just in case of future misunderstanding, when I’m writing this WSL2 hasn’t come out yet.

Now I’m using ArchLinux, but I’ve been using Windows 10 for several months. And of course, I use WSL every day. From a single command to coding a (not very) big project, WSL is just easy and comfortable to use than the native Windows command line, especially for coding stuff. I use CLion and my heavily customized VIM in WSL. CLion for relatively bigger C/C++ projects, and VIM for small things and other languages, like assembly and markdown, for example. About Python? I just use PyCharm with Windows python, it’s no big difference.

Sounds perfect?

The problem is, some times I still need to use commands like dd and losetup which are not fully supported in WSL, like when you are burning your compiled assembly onto disk image files and booting stuffs in QEMU. Just as an example. You may find something you can’t do in WSL but can in a REAL VM. Then you are in a dilemma: WSL’s so convenient, you’ve already configured it to suit you needs, but a few commands just stall you from doing all your work in it. A VM is a heavy thing, you don’t like to work in it all time.

My solution: SSH + shared folders

WSL works well with SSH, so why not boot a VM, put it aside, and access it in WSL using SSH? Install guest addition, setup shared folders, then you’ll have the same feeling as working in WSL. But this time all stuff works because it’s real Linux. And, you don’t need all you toolchains installed in the VM, you can just do the losetup and dd in VM, then run the QEMU in WSL as usual, so no need to install QEMU in you VM!

Also, since your VM is just to be put aside and accessed by SSH, running simple commands, you can just close the GUI, it’ll save a lot of processor time and (maybe) memory. Allocate it 20G disk space and 1G RAM, it’ll be enough. It’s a bless for low-end laptops.

3. VM + CHROOT

I know there are many better solutions for this, but …(I don’t have a good excuse here, but I just did all these stuff…)

Another case: I’m using Debian, but I want to use certain softwares that runs better on Deepin Linux, like QQ and WeChat. Many Chinese Linux users may meet this problem. I don’t want to use a heavy VM just to run simple softwares. Actually maybe after a painful tweaking to solve those libraries and dependencies, I can run the softwares directly on Debian, but the time spent doesn’t worth it, and I may not have that ability. Like I can install rpm on Debian using some fancy tools after trying for a day or two, but the procedure is just too inconvenient to be a part of everyday life.

They are both Linux, it’s awful to be unable to run softwares from another distro. So, why not have a try of chroot?

First, install a Linux VM as usual, it may be Deepin, Fedora, or whatever your app runs on. Then, mount the virtual disk in your host machine, bind mount system partitions, setup correct display, chroot, and run whatever you want.

As an example, here are some parts of my script:

Mount the VMDK file.

vdfuse -w -f "$VMDISK_PATH" "$VMDISK_MOUNT_PATH"

Use host network configuration:

function updateresolv()
{
	mv -f $DEEPIN_ROOT/etc/resolv.conf{,.bak}
	cp -a /var/run/NetworkManager/resolv.conf $DEEPIN_ROOT/etc/resolv.conf
	echo "-->update resolv.conf done: $?"
}

Setup display:

	export DISPLAY=:0
	xhost +local:

Run WeChat in Deepin wine:

			chroot $DEEPIN_ROOT su $U -c "env WINEPREFIX=/home/$U/.deepinwine/Deepin-WeChat/ $DWINE \"C:\\Program Files\\Tencent\\WeChat\\WeChat.exe\"" &

where $U is my username.

It works, but not without problems. The Chinese input method just won’t work in the chroot-ed windows, and fonts are a little bit weird. But anyway, it works. Things like deepin-terminal works without any problem. And with a bind mount of your home directory, file access is easier than in VM.

By the way, there is a tool called xchroot (or arch-chroot in ArchLinux) that can automatically do those bind mounts.

4. “Dual” boot with GRUB

Scenario: You have migrated to Linux, but still need to use Windows in VM sometimes. You hate reboot your computer to another OS, closing all those working windows which have already filled several virtual desktops.

Your VM, maybe a Windows 7 with some basic softwares installed, is enough for daily use, but it’s far from complete compared to the (maybe Win10) Windows installed on your physical disk. So, do you feel excited if you can boot the Windows lying in physical disk directly in VM, while also be able to boot it physically? Actually, it’s quite possible (and simple) to do so. There are many tutorials about this. Just make sure you have chosen the right partition, and don’t make silly mistakes, your data will be safe, at least in my case. I do have lost some data in other cases but not in this case. By saying this I mean I won’t be responsible for your data loss.

The problem is, having the VM using a physical disk partition is quite simple, but let Windows boot correctly is not.

As by default, Win10 is install to a big NTFS partition, but it’s bootloader is placed in the EFI partition, shared with Linux, which is mounted on /boot/efi in Linux. So, things will be simpler if you keep the EFI partition mounted in Linux, passing only the NTFS partition to VM. But now how can the VM boot? No worries, GRUB will do it. Having a grub ISO file and a Windows installation ISO file at hand, then all difficulties will disappear.

The grub ISO file can be made by grub-mkrescue -o grub.iso command. Or simpler, just take a Ubuntu (or other distro) LiveCD, it’ll contain a grub bootloader, boot the LiveCD, press c at the boot menu, then there will be a grub commandline. With a grub commandline, you have power to boot other EFI files(Like Windows bootloader), directly load and boot Linux, load another grub, boot directly into ISO LiveCD, and much more. Maybe I’ll write a passage on this later?

So do you think this configuration is safe, or it will corrupt your drive one day?

For me it’s pretty safe. I did a lot of bad stuffs, including force reboot(both host and guest), force shutdown during Windows Update, and delete then recreate the Windows boot loader accidentally. If I shutdown Windows by force during update when running physically, then boot it in VM, Windows may fail to boot. But this can be easily solved by run it again physically and let everything finish. Sometimes I need a chkdsk in Windows. But I never used the Windows C: volume in Linux while running the Windows in the volume in a VM: this may cause damage!!!

Am I satisfied?

However, I don’t use this configuration frequently, because Win10 has too much stuff running in the background( mostly spyware and malware I guess =) ), so my laptop heats a lot and the fan keeps running at high speed. I hate both.

Win7 is better for me. But probably Win7 cannot be booted both in VM and physical machine as Win10. I tried it but failed, and didn’t try further, though I think I can succeed. I gave up partly because my 8th generation Intel processor does not officially support Win7. And as Virtualbox doesn’t support Win7 to boot in UEFI mode but I prefer Virtualbox to VMWare and others. Why UEFI mode? because my disk is GPT, it also shows up as GPT in VM, and GPT disk doesn’t support BIOS boot. If you really want to try disk, think twice. What I get best is, I copied the Win7 in Virtualbox to a physical partition(GPT disk), setup UEFI boot in VMWare successfully, then I tried to boot this monster physically. Really crazy. It went to black screen, but I can here the boot sound, and after typing Windows+R then shutdown /s /t 0 then Enter, I can here the shutdown sound and the computer turned off peacefully. It’s the driver problem I thought, if I were able to inject drivers, I may succeed, and I’m really close to success. Tired of it though. Never want to try again.

Also, this requires you to run the VM as root because reading physical partitions needs root. And as my primary VM, I wants to share host folders with the VM. But the VM runs as root, the files the VM created is owned by root, but the folders I want to share belongs to me the user, not me the root. These permission problems are awful.

5. “Dual” Boot VHD

Again, you want to boot something(probably Windows) both physically and in VM. And you are not satisfied with dealing with partitions: so, what if you can store a whole OS in a file? VHD does it. Windows can be install into a VHD file, and the file can be booted physically, or in virtual machine softwares like virtualbox and hypervisor. If you are fortunate enough, you can boot the file both in VM and physically! Win10 VHDs will definitely do this, and Win10 will adjust itself for the new hardware environments. But Win7 will probably fail, the driver just sucks. I tried really hard, but never succeed, it will just BSOD no matter what I do.

Some tips:

  • Win7 ultimate and home edition cannot do the boot, only enterprise can do. But there are softwares to circumvent it.

  • The VHD will expand to it’s maximum size when being boot physically, and shrink after shutdown. So make sure you have enough space.
  • Again, you need to first attach the VHD in Windows(maybe WinPE) and create a boot loader before you can boot the system.

My other blog passage “SCGY机房还原系统：本地部分” contains some further information about booting VHD and its application(Computer room restoration project).

6. Wanna have a taste of macOS?

Despite extremely low graphical performance, macOS can run in VM! I can run macOS High Sierra in Virtualbox without any problems. You can easily download a installation disk on google drive and follow a detailed tutorial telling you how to make the OS think that you are running it on Apple’s hardware.

I didn’t investigate further, and don’t know whether graphical performance can be increased with other cheatings. But if you just want to have a look of the system, or register an AppleID using Safari, or run some commands that runs only on macOS, you can do it.

7. GPU intensive jobs on Linux?

So, it comes to GPU passthrough. I tried twice and failed twice. Hours spent and tens of gigabytes of disk space used, nothing happened at all. May be one day on desktop PCs I can succeed? Now I have given up trying to do this on my laptop which has a low-end AMD GPU. I’ll having difficulty running Photoshop in VM due to lack of graphic memory, but actually I seldom use Photoshop, don’t I?

But don’t be afraid… Many people on the Internet have done it successfully, and detailed tutorials are available everywhere. Waiting for your(and my) good news!

May update later…

I’ll update this if I find other interesting uses of virtual machines!