Upgrading from FreeBSD Unix 8.0 to 9.0 with ‘integrity error’ fix handled

There is a fast and easy way to upgrade your FreeBSD installation to 9.0 latest release candidate. This article assumes you are using 8.0 RELEASE but its quite applicable to older versions also.

Make sure your existing ports are up to date

sudo portsnap fetch update

sudo portmaster -Da

Upgrade FreeBSD to 9.0

sudo freebsd-update upgrade -r 9.0-RELEASE

If all goes well then FreeBSD will start downloading the metapackages and files. If you are unlucky enough to see the error message:

The update metadata is correctly signed, but
failed an integrity check.
Cowardly refusing to proceed any further.

then the solution is to fix the error in freebsd-update package:

sed -i '' -e 's/=_/=%@_/' /usr/sbin/freebsd-update

This is recommended in the official release patch list and it is explained as:

...a minor change must be made to the freebsd-update code in order
for it to accept file names appearing in FreeBSD 9.0 which contain the '%'
and '@' characters; without this change, freebsd-update will error out
with the message "The update metadata is correctly signed, but failed an
integrity check".

After executing the above, run the freebsd-upgrade command again and everything will work.