本文為原創，原文地址： http://blog.csdn.net/duanlove/article/details/54666441

作業系統（Ubuntu server）環境：

# uname -a
Linux ubuntu 3.16.0-23-generic #31-Ubuntu SMP Tue Oct 21 17:56:17 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux


# lsb_release  -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.10
Release:        14.10
Codename:       utopic

網路搜尋關鍵詞：

1、  Ubuntu 報錯 The following packages have unmet dependencies；

2、  Ubuntu server 14.10 即使替換源也無法解決安裝軟體的依賴問題；

3、  Ubuntu server 14.10 原始官方源 apt-get update 報錯， 顯示 如下錯誤“W: Failed to fetch  $URL  Packages  404  Not Found [IP: 137.189.4.14 80]  E: Some index files failed to download. They have been ignored, or old ones used instead.

4、  Ubuntu 部分軟體可以安裝成功，但是某些軟體（如開發類依賴libc6庫的軟體）報依賴錯誤，無法安裝成功；

報錯提示：

The following packages have unmet dependencies:
 libc6-dev : Depends: libc6 (= 2.19-0ubuntu6.9) but 2.19-10ubuntu2 is to be installed
E: Unable to correct problems, you have held broken packages.

以上報錯的含義是：

    libc6-dev: 依賴: libc6的 “ 2.19-0ubuntu6.9”版本， 但是系統已安裝的是 “2.19-10ubuntu2” 。 

理解了這層意思之後，接下來問題就迎刃而解 了。

報錯命令及全文：

[email protected]:/etc/apt# apt-get install build-essential
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:


The following packages have unmet dependencies:
 build-essential : Depends: libc6-dev but it is not going to be installed or
                            libc-dev
                   Depends: g++ (>= 4:4.4.3) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

-------------------------------------

[email protected]:/etc/apt# apt-get install zlib1g-dev libc6-dev libc-dev libmysqlclient-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'libc6-dev' instead of 'libc-dev'
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libc6-dev : Depends: libc6 (= 2.19-0ubuntu6.9)but 2.19-10ubuntu2 is to be installed
E: Unable to correct problems, you have held broken packages.

-------------------------------------

[email protected]:/etc/apt# apt-get install zlib1g-dev libc6-dev libc-dev libmysqlclient-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'libc6-dev' instead of 'libc-dev'
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libc6-dev : Depends: libc6 (= 2.19-0ubuntu6.9) but 2.19-10ubuntu2 is to be installed
E: Unable to correct problems, you have held broken packages.


解決方案：

檢視以安裝的libc
[email protected]:/etc/apt# dpkg -l | grep libc6
ii  libc6:amd64                         2.19-10ubuntu2                     amd64        GNU C Library: Shared libraries


問題在於，當前系統以安裝的 libc6的版本為“2.19-10ubuntu2 ” ，而我們安裝其他軟體（包括build-essential 、g++等）的時候，所依賴的是“2.19-0ubuntu6.9” 。

也就是問題在於， 依賴的某個軟體的版本，跟系統以安裝的版本不一致。但 apt-get又不會自動去解除安裝以安裝的自動安裝上依賴的目標版本。 所以導致我們需要手動去解決這個問題。  當前解決這個問題辦法有很多種，我們這裡選擇了，直接強制覆蓋安裝目標版本，替代原來系統已安裝的版本。


# apt-get install  libc6=2.19-0ubuntu6.9
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  glibc-doc
The following packages will be DOWNGRADED:
  libc6
0 upgraded, 0 newly installed, 1 downgraded, 0 to remove and 77 not upgraded.
Need to get 4,717 kB of archives.
After this operation, 37.9 kB disk space will be freed.
Do you want to continue? [Y/n] Y
Get:1 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security/main libc6 amd64 2.19-0ubuntu6.9 [4,717 kB]
Fetched 4,717 kB in 0s (8,235 kB/s)
Preconfiguring packages ...
dpkg: warning: downgrading libc6:amd64 from 2.19-10ubuntu2 to 2.19-0ubuntu6.9
(Reading database ... 69479 files and directories currently installed.)
Preparing to unpack .../libc6_2.19-0ubuntu6.9_amd64.deb ...
Unpacking libc6:amd64 (2.19-0ubuntu6.9) over (2.19-10ubuntu2) ...
Setting up libc6:amd64 (2.19-0ubuntu6.9) ...
Processing triggers for libc-bin (2.19-10ubuntu2) ...
 

再檢視libc6的已安裝資訊：

[email protected]:/etc/apt# dpkg -l | grep libc6
ii  libc6:amd64                         2.19-0ubuntu6.9                     amd64        Embedded GNU C Library: Shared libraries


再安裝其他原來安裝過程報類似錯誤的軟體：

# apt-get install zlib1g-dev libc6-dev libc-dev libmysqlclient-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'libc6-dev' instead of 'libc-dev'
The following extra packages will be installed:
  libc-dev-bin libmysqlclient18 linux-libc-dev manpages-dev mysql-common
Suggested packages:
  glibc-doc
The following NEW packages will be installed:
  libc-dev-bin libc6-dev libmysqlclient-dev linux-libc-dev manpages-dev zlib1g-dev
The following packages will be upgraded:
  libmysqlclient18 mysql-common
2 upgraded, 6 newly installed, 0 to remove and 75 not upgraded.
Need to get 6,234 kB of archives.
After this operation, 24.7 MB of additional disk space will be used.
Do you want to continue? [Y/n] Y
Get:1 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security/main mysql-common all 5.5.54-0ubuntu0.14.04.1 [13.0 kB]
Get:2 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security/main libmysqlclient18 amd64 5.5.54-0ubuntu0.14.04.1 [597 kB]
Get:3 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security/main libc-dev-bin amd64 2.19-0ubuntu6.9 [69.0 kB]
Get:4 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-proposed/main linux-libc-dev amd64 3.13.0-108.155 [772 kB]
Get:5 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security/main libc6-dev amd64 2.19-0ubuntu6.9 [1,910 kB]
Get:6 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty/main zlib1g-dev amd64 1:1.2.8.dfsg-1ubuntu1 [183 kB]
Get:7 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security/main libmysqlclient-dev amd64 5.5.54-0ubuntu0.14.04.1 [869 kB]
Get:8 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty/main manpages-dev all 3.54-1ubuntu1 [1,820 kB]
Fetched 6,234 kB in 1s (5,609 kB/s)
(Reading database ... 69479 files and directories currently installed.)
Preparing to unpack .../mysql-common_5.5.54-0ubuntu0.14.04.1_all.deb ...
Unpacking mysql-common (5.5.54-0ubuntu0.14.04.1) over (5.5.40-0ubuntu1) ...
Preparing to unpack .../libmysqlclient18_5.5.54-0ubuntu0.14.04.1_amd64.deb ...
Unpacking libmysqlclient18:amd64 (5.5.54-0ubuntu0.14.04.1) over (5.5.40-0ubuntu1) ...
Selecting previously unselected package libc-dev-bin.
Preparing to unpack .../libc-dev-bin_2.19-0ubuntu6.9_amd64.deb ...
Unpacking libc-dev-bin (2.19-0ubuntu6.9) ...
Selecting previously unselected package linux-libc-dev:amd64.
Preparing to unpack .../linux-libc-dev_3.13.0-108.155_amd64.deb ...
Unpacking linux-libc-dev:amd64 (3.13.0-108.155) ...
Selecting previously unselected package libc6-dev:amd64.
Preparing to unpack .../libc6-dev_2.19-0ubuntu6.9_amd64.deb ...
Unpacking libc6-dev:amd64 (2.19-0ubuntu6.9) ...
Selecting previously unselected package zlib1g-dev:amd64.
Preparing to unpack .../zlib1g-dev_1%3a1.2.8.dfsg-1ubuntu1_amd64.deb ...
Unpacking zlib1g-dev:amd64 (1:1.2.8.dfsg-1ubuntu1) ...
Selecting previously unselected package libmysqlclient-dev.
Preparing to unpack .../libmysqlclient-dev_5.5.54-0ubuntu0.14.04.1_amd64.deb ...
Unpacking libmysqlclient-dev (5.5.54-0ubuntu0.14.04.1) ...
Selecting previously unselected package manpages-dev.
Preparing to unpack .../manpages-dev_3.54-1ubuntu1_all.deb ...
Unpacking manpages-dev (3.54-1ubuntu1) ...
Processing triggers for man-db (2.7.0.2-2) ...


從以上安裝過程看出來，成功安裝了。  

我們再次執行如下命令 通過dpkg來查詢具體安裝資訊：


[email protected]:/etc/apt# dpkg -l | grep -E "zlib1g-dev|libc6-dev|libc-dev|libmysqlclient-dev"
ii  libc-dev-bin                        2.19-0ubuntu6.9                     amd64        Embedded GNU C Library: Development binaries
ii  libc6-dev:amd64                     2.19-0ubuntu6.9                     amd64        Embedded GNU C Library: Development Libraries and Header Files
ii  libmysqlclient-dev                  5.5.54-0ubuntu0.14.04.1             amd64        MySQL database development files
ii  linux-libc-dev:amd64                3.13.0-108.155                      amd64        Linux Kernel Headers for development
ii  zlib1g-dev:amd64                    1:1.2.8.dfsg-1ubuntu1               amd64        compression library - development

再次確認build-essential  是否可以成功安裝：

# dpkg -l | grep build-essential

當前系統沒有安裝 build-essential。

# dpkg -l | grep g++
當前系統沒有安裝 g++。

# dpkg -l | grep gcc
ii  gcc                                 4:4.8.2-1ubuntu6                    amd64        GNU C compiler
ii  gcc-4.8                             4.8.4-2ubuntu1~14.04.3              amd64        GNU C compiler
ii  gcc-4.8-base:amd64                  4.8.4-2ubuntu1~14.04.3              amd64        GCC, the GNU Compiler Collection (base package)
ii  gcc-4.9-base:amd64                  4.9.1-16ubuntu6                     amd64        GCC, the GNU Compiler Collection (base package)
ii  libgcc-4.8-dev:amd64                4.8.4-2ubuntu1~14.04.3              amd64        GCC support library (development files)
ii  libgcc1:amd64                       1:4.9.1-16ubuntu6                   amd64        GCC support library

安裝 build-essential （g++也會被附帶安裝，所以只要安裝這個基礎套件，基本的編譯環境就ok了）： 
# apt-get install build-essential
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  g++ g++-4.8 libstdc++-4.8-dev
Suggested packages:
  g++-multilib g++-4.8-multilib gcc-4.8-doc libstdc++6-4.8-dbg libstdc++-4.8-doc
The following NEW packages will be installed:
  build-essential g++ g++-4.8 libstdc++-4.8-dev
0 upgraded, 4 newly installed, 0 to remove and 75 not upgraded.
Need to get 19.2 MB of archives.
After this operation, 40.1 MB of additional disk space will be used.
Do you want to continue? [Y/n] Y
Get:1 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security/main libstdc++-4.8-dev amd64 4.8.4-2ubuntu1~14.04.3 [1,053 kB]
Get:2 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty-security/main g++-4.8 amd64 4.8.4-2ubuntu1~14.04.3 [18.1 MB]
Get:3 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty/main g++ amd64 4:4.8.2-1ubuntu6 [1,490 B]
Get:4 http://ftp.cuhk.edu.hk/pub/Linux/ubuntu/ trusty/main build-essential amd64 11.6ubuntu6 [4,838 B]
Fetched 19.2 MB in 1s (9,947 kB/s)
Selecting previously unselected package libstdc++-4.8-dev:amd64.
(Reading database ... 72784 files and directories currently installed.)
Preparing to unpack .../libstdc++-4.8-dev_4.8.4-2ubuntu1~14.04.3_amd64.deb ...
Unpacking libstdc++-4.8-dev:amd64 (4.8.4-2ubuntu1~14.04.3) ...
Selecting previously unselected package g++-4.8.
Preparing to unpack .../g++-4.8_4.8.4-2ubuntu1~14.04.3_amd64.deb ...
Unpacking g++-4.8 (4.8.4-2ubuntu1~14.04.3) ...
Selecting previously unselected package g++.
Preparing to unpack .../g++_4%3a4.8.2-1ubuntu6_amd64.deb ...
Unpacking g++ (4:4.8.2-1ubuntu6) ...
Selecting previously unselected package build-essential.
Preparing to unpack .../build-essential_11.6ubuntu6_amd64.deb ...
Unpacking build-essential (11.6ubuntu6) ...
Processing triggers for man-db (2.7.0.2-2) ...
#

安裝過程成功走完，並且無任何報錯提示。

檢查 build-essential   和 g++是否成功安裝：

# dpkg -l | grep -E "build-essential|g\+\+"
ii  build-essential                     11.6ubuntu6                         amd64        Informational list of build-essential packages
ii  g++                                 4:4.8.2-1ubuntu6                    amd64        GNU C++ compiler
ii  g++-4.8                             4.8.4-2ubuntu1~14.04.3              amd64        GNU C++ compiler 

確定已成功安裝！！！！

最終問題解決。

補充：

     這裡有個深層次的原因： Ubuntu 14.10 版本在當前（2016/2017）已經從維護名單裡面去除了，相應的源也不再支援，所以導致原始匹配版本的源無法使用，ping不通伺服器ip。 而我這裡配置的是 14.04對應的源， 其安裝軟體時依賴的版本是與 14.10是有差異的，所以導致 安裝一些軟體的時候， 依賴的軟體的版本總是比當前系統已經安裝的版本要低。 導致依賴衝突，最終導致安裝軟體無法順利進行。