[Buildroot] [PATCH] fs/ext2: further fix to the UUID
Peter Korsgaard
jacmet at uclibc.org
Tue May 28 22:19:04 UTC 2013
>>>>> "Yann" == Yann E MORIN <yann.morin.1998 at free.fr> writes:
Yann> From: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Yann> Turned out that setting a nil-UUID is no better than clearing it.
Yann> What currently happens is as follows:
Yann> - first, genext2fs does not generate a UUID
Yann> - then we tune2fs to upgrade the filesystem
Yann> - then we run fsck, which generates a random UUID
Yann> - then we re-run tune2fs to set a nil-UUID
Yann> So, on the target, if the file system is improperly unmounted (eg.
Yann> with a power failure), on next boot, fsck may be run, and a new
Yann> random UUID will be generated.
Yann> *However*, fsck improperly updates the filesystem when it adds the
Yann> UUID, and there are a few group descriptor checksum errors.
Yann> Those errors will go undetected until the next fsck, which will then
Yann> block for user input (bad on embedded systems, bad).
Yann> Fix that by systematically generating a random UUID _before_ we call
Yann> to fsck.
Yann> A random UUID is not so bad, after all, since there are already so
Yann> many sources of unpredictability in the filesystem: files date and
Yann> ordering, files content (date, paths...) which renders a fixed UUID
Yann> unneeded.
Yann> And it is still possible to set the UUID in a post-image script if
Yann> needed, anyway.
Committed, thanks.
--
Bye, Peter Korsgaard
More information about the buildroot
mailing list