我在新的 Debian jessie 系统上并尝试安装 lvm2：
# apt-get install lvm2
The following packages have unmet dependencies:
lvm2 : Depends: watershed (>= 2) but it is not going to be installed
E: Unable to correct problems, you have held broken packages
apt-get update、、、upgrade等-f没有autoremove帮助，最重要的是，我的分水岭版本是7：
# aptitude versions watershed
Package watershed:
i 7
如何安装lvm2？