Comment 1 for bug 609280

I tried to follow this guide :

http://grub.enbug.org/Grub2LiveCdInstallGuide

to enter as root into my installed system, and reinstall grub properly.

It tells me that it can not create /dev/null (permission denied), but /dev/null is present on the hard drive (see picture joined), grub-pc is well installed, and it is impossible to update-grub ("cannot find a device for /")