当我进行到安装automake时出错？？

zx427

当我安装automake时，
运行到./configure prefix=/usr 时，
终端输出提示出错：
configure:error:autoconf 2.54 or better is required.
  is it installed? is it in your path? (try running 'autoconf --version')is it working? see also config.log for error message before this one.
请问这是怎么回事？？？
我确信已经安装了autoconf了，而且版本是2.57。