我试图在Ubuntu 14.04安装卡桑德拉和我面临的，当我运行这个命令这个问题：sudo apt-get install cassandra。
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package cassandra is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or is only available from another source
E: Package 'cassandra' has no installation candidate
请帮我修复它。尝试了一些链接，但没有奏效。我需要在我的机器上安装 cassandra
我不小心从中删除MySQL了Ubuntu 16.04.现在当我再次尝试安装时,会出现错误.请帮我解决这个错误:
update-alternatives: error: alternative path /etc/mysql/my.cnf.fallback doesn't exist
dpkg: error processing package mysql-common (--configure):
subprocess installed post-installation script returned error exit status 2
E: Sub-process /usr/bin/dpkg returned an error code (1)