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i have been using windows xp and ubuntu natty using dual boot. it has run perfectly until one day when i tried to boot ubuntu i am getting the busy box shell. i dont know what that is :( when i try to restart,

  1. the following options come up.

    1. ubuntu 11.04

    2. ubuntu recovery

    3. mem test

    4. another mem test

    5. win xp pro

when i try to open win xp it opens perfectly..

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Could you take a screenshot (possibly with a camera or your phone)? – Lekensteyn Jul 27 '11 at 11:08
Apparently, wubi doesn't work if you install it on a non-primary partition. If you have multiple partitions, try installing it on your windows "C:" drive. – user28939 Oct 19 '11 at 12:20

Busybox shell fallback occurs during the boot cycle when the root partition cannot be located, fails to mount, and/or the /sbin/init binary cannot be located on it.

Sometimes this is due to hardware failure, a loose connection, or other corruption. That causes the root partition to fail to mount.

Most commonly, this is due to a typo or mistake in grub. Take a look at the file /boot/grub/grub.cfg (in Grub2, which most users have migrated to. If you don't have the file, then you're using the older version of Grub).

There's a very good troubleshooting guide for Grub2 at

Basically, look for the like that says something like (there's one line like this for each choice in the grub menu):

linux /boot/vmlinuz-2.6.31-11-generic root=UUID=cb201140-52f8-4449-9a95-749b27b58ce8 ro quiet splash

Most problems are on this line. A typo or mistake on this like will kick you out to busybox.

1) Make sure the /boot/vmlinuz-$version line on that file is correct.

2) Use the 'blkid' command to check the disk UUIDs. Make sure the UUID matches the drive you want to boot from.

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