freebsd 10.1下通过ports安装软件提示ALLOW_UNSUPPORTED_SYSTEM.

今天在一台freebsd 10.1 amd64的系统上通过ports安装软件提示以下错误信息:
/!\ ERROR: /!\

Ports Collection support for your FreeBSD version has ended, and no ports are
guaranteed to build on this system. Please upgrade to a supported release.

No support will be provided if you silence this message by defining
ALLOW_UNSUPPORTED_SYSTEM.
解决方案是升级系统到当前最新的10.3-RELEASE版本:
[email protected]:~ # freebsd-version -k
10.1-RELEASE
[email protected]:~ # freebsd-version -u
10.1-RELEASE
[email protected]:~ # freebsd-update upgrade -r 10.3-RELEASE
[email protected]:~ # freebsd-update install
[email protected]:~ # reboot
[email protected]:~ # freebsd-update install
[email protected]:~ # reboot
End!