用ports安装如何指定服务器

• CODE:
• 
  MASTER_SITE_BACKUP?=  
  ftp://202.113.12.9/pub/FreeBSD/ports/distfiles/${DIST_SUBDIR}/ 
  ftp://ftp.freebsd.org.cn/pub/FreeBSD/ports/distfiles/${DIST_SUBDIR}/ 
  ftp://ftp.freebsdchina.org/pub/FreeBSD/ports/distfiles/${DIST_SUBDIR}/
  MASTER_SITE_OVERRIDE?= ${MASTER_SITE_BACKUP}
  

TAG: FreeBSD 操作系统