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I want to install Ubuntu by Wubi. But when I reboot to finish installation, it returns this:

(initramfs)stdin:I/O error
/scripts/casper-premount/20iso_scan:line46:can't open /dev/sr0: No medium found 
Could not find the ISO /ubuntu/install/instalation.iso

This could also happen if the file system is not clean because of an operating system crash, an interrupted boot process,an improper shutdown, or unplugging of a removable device without first unmounting or ejecting it, 
To fix this, simply reboot into windows,let it fully start,log in, run"chkdsk /r",then gracefully shut down and reboot back into windows.

After this you should you should be able to reboot again and resume the installation.

I have tried running chkdsk, but it didn`t work.what should I do?

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If you're running Wubi from a DVD*** then the only option you get now is to either Reboot and boot from the DVD or to use the CD boot helper.

This second option is most likely what you selected and this instructs Wubi to help you boot from the DVD, for people who don't know how or cannot override their BIOS boot order. But this also requires that you leave the DVD in the optical drive when you reboot. If you don't leave it in, you get this error.

What you likely wanted was the now hidden middle option, to Install inside Windows. This is suppressed when you're running Wubi from the DVD and to get it you have to run Wubi with the --force-wubi option. So if your DVD is drive E: then you would go to a command prompt and run E:\wubi.exe --force-wubi.

***I'm saying DVD instead of CD because the ISO doesn't fit on a CD anymore, but it's still referred to as the CD boot helper in Wubi.

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