Freebsd make install clean checksum error

在使用ports tree安装软件时候，如果遇到checksum不正确无法继续安装的时候，可以试试更换一下ports 下载源，重新下载安装.

vi /etc/make.conf

MASTER_SITE_BACKUP?= \
http://ports.hshh.org/${DIST_SUBDIR}/\
ftp://ftp.freebsdchina/pub/FreeBSD/ports/distfiles/${DIST_SUBDIR}/\
ftp://ftp.freebsdchina/pub/FreeBSD/distfiles/${DIST_SUBDIR}/\
ftp://140.113.17.209/pub/ports/distfiles/${DIST_SUBDIR}/\
ftp://140.113.17.209/pub/distfiles/${DIST_SUBDIR}/
MASTER_SITE_OVERRIDE?= ${MASTER_SITE_BACKUP}

make clean

make install clean