On Tue, Feb 08, 2011 at 01:01:36AM +1100, Sridhar Dhanapalan wrote: > Are OS images checked for integrity by the XO before they are written > to the flash storage? I suspect not.
As Chris said, yes. The image is checked for transmission integrity *as* it is written to the flash storage [1], not before. A transmission error will result in a partially written internal storage. The laptop should not be used until a successful install occurs. It may appear to work but fail later. For XO-1.5, the .zd format contains block hashes [2]. If the data in these blocks do not match the hash, the fs-update ceases with an error: Bad hash for eblock# Your USB key may be bad. Please try a different one. See http://wiki.laptop.org/go/Bad_hash This should detect bit errors in downloads. There are other possible errors too, such as "Short read of zdata file" which will happen if the file is incompletely downloaded. > The schools we deal with don't always have reliable Internet, so some > failsafe mechanism to prevent them from using damaged images would be > helpful. We can't expect them to learn md5sum to check the image first > - that is too technical. You should give them the option. You never know when you have a school teacher or aid who has a clue, and it would save them repeating the huge download. I suggest you capture the output after a successful fs-update for use in your instructions, along with a comment that "anything else is bad, please ask for help." The output is different for signed installs using deployment keys. References: 1. http://tracker.coreboot.org/trac/openfirmware/browser/cpu/x86/pc/olpc/via/fsupdate.fth#L159 checks the hash, 2. git://dev.laptop.org/bios-crypto file zhashfs.c creates the hash. -- James Cameron http://quozl.linux.org.au/ _______________________________________________ Devel mailing list [email protected] http://lists.laptop.org/listinfo/devel
