root@i-v0dxq3zy:/etc/apt# apt-get install openssh-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
openssh-client
Suggested packages:
ssh-askpass libpam-ssh keychain monkeysphere openssh-blacklist openssh-blacklist-extra rssh molly-guard ufw
The following packages will be upgraded:
openssh-client openssh-server
2 upgraded, 0 newly installed, 0 to remove and 286 not upgraded.
Need to get 1,282 kB of archives.
After this operation, 1,024 B of additional disk space will be used.
Do you want to continue [Y/n]? y
Get:1 http://cn.archive.ubuntu.com/ubuntu/ precise-security/main openssh-server amd64 1:5.9p1-5ubuntu1.10 [339 kB]
Get:2 http://cn.archive.ubuntu.com/ubuntu/ precise-security/main openssh-client amd64 1:5.9p1-5ubuntu1.10 [943 kB]
Fetched 1,282 kB in 1s (1,140 kB/s)
Preconfiguring packages ...
(Reading database ... 71251 files and directories currently installed.)
Preparing to replace openssh-server 1:5.9p1-5ubuntu1.1 (using .../openssh-server_1%3a5.9p1-5ubuntu1.10_amd64.deb) ...
Unpacking replacement openssh-server ...
dpkg: error processing /var/cache/apt/archives/openssh-server_1%3a5.9p1-5ubuntu1.10_amd64.deb (--unpack):
unable to make backup link of `./usr/sbin/sshd' before installing new version: Operation not permitted
Preparing to replace openssh-client 1:5.9p1-5ubuntu1.1 (using .../openssh-client_1%3a5.9p1-5ubuntu1.10_amd64.deb) ...
Unpacking replacement openssh-client ...
dpkg: error processing /var/cache/apt/archives/openssh-client_1%3a5.9p1-5ubuntu1.10_amd64.deb (--unpack):
unable to make backup link of `./usr/bin/ssh' before installing new version: Operation not permitted
dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Processing triggers for ureadahead ...
Errors were encountered while processing:
/var/cache/apt/archives/openssh-server_1%3a5.9p1-5ubuntu1.10_amd64.deb
/var/cache/apt/archives/openssh-client_1%3a5.9p1-5ubuntu1.10_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

两个途径，一，找老版本下可用的源。

二，翻墙后update

现在用的就是老版本的源

1. 一般使用者以為使用 root 登入 權限最大 沒有什麼事 不能做
1-1. 在 Ubuntu 這可能是一個錯誤的想法

2. 新手
建議使用 安裝 Ubuntu 時 創設的帳號登入 下達指令
2-1. 權限不足 需要 root 權限時
sudo 文字指令
gksudo gnome-圖形指令
kdesudo kde-圖形指令

3. 參見
viewtopic.php?p=3196839#p3196839

4. 建議
使用 安裝 Ubuntu 時 創設的帳號登入