安装软件遇到情况，一直等待：
root@test-xxx:/opt# apt-get install vsftpd
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
ssl-cert
Suggested packages:
openssl-blacklist
The following NEW packages will be installed:
ssl-cert vsftpd
0 upgraded, 2 newly installed, 0 to remove and 17 not upgraded.
Need to get 130 kB of archives.
After this operation, 477 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
0% [Waiting for headers]
进行apt-get update，也是一直等到
root@test-xxx:/etc/apt# apt-get update
0% [Waiting for headers] [Waiting for headers]
按照网上说法，更换源，问题未修复。
之后又找到一说法，删除/var/cache/apt/archives/partial目录，问题未修复。
但是，发现/var/cache/apt/archives/下有一个‘lock’文件。删除，问题解决。
看来，遇到问题自己分析一下，是很有必要的。