使用 freebsd-update 升級 FreeBSD 時，如果出現以下的錯誤：
The update metadata is correctly signed, but failed an integrity check. Cowardly refusing to proceed any further.
可以參考這邊的說明http://www.freebsd.org/security/advisories/FreeBSD-EN-12:01.freebsd-update.asc，大概是說，只要你是從 9.0 以前的版本，升級到 9.0 以後的版本，就會出現這個問題。
不同的版本，有不一樣的解決方式，蠻麻煩的，看看吧。
改好之後，就可以順利更新了:
[root@xxxx]/usr/src/usr.sbin/freebsd-update(106): freebsd-update -r 10.0-RELEASE upgrade Looking up update.FreeBSD.org mirrors... 5 mirrors found. Fetching metadata signature for 7.4-RELEASE from update6.freebsd.org... done. Fetching metadata index... done. Inspecting system... done. The following components of FreeBSD seem to be installed: kernel/generic src/base src/bin src/cddl src/contrib src/crypto src/etc src/games src/gnu src/include src/krb5 src/lib src/libexec src/release src/rescue src/sbin src/secure src/share src/sys src/tools src/ubin src/usbin world/base world/dict world/info world/lib32 world/manpages world/proflibs The following components of FreeBSD do not seem to be installed: world/catpages world/doc world/games Does this look reasonable (y/n)? y Fetching metadata signature for 10.0-RELEASE from update6.freebsd.org... done. Fetching metadata index... done. Inspecting system... done. Fetching files from 7.4-RELEASE for merging... done. Preparing to download files... done. Fetching 7714 patches.....10....20....30....40....50....60....70....80....90....100....110....120....