（问题解决篇）ubuntu更新时，出现错误E: Some index files failed to download。。。

hege

　　在ubuntu更新时，出现错误E: Some index files failed to download.They have been ignored, or old ones used instead.
在sudo apt-get update的时候出现了下列问题：
　　root@0cc8c10d217a:~# sudo apt-get update
　　sudo: unable to resolve host 0cc8c10d217a
　　Err http://archive.ubuntu.com trusty InRelease
　　Err http://archive.ubuntu.com trusty-security InRelease
　　Err http://archive.ubuntu.com trusty-updates InRelease
　　Err http://archive.ubuntu.com trusty-proposed InRelease
　　Err http://archive.ubuntu.com trusty-backports InRelease
　　Err http://archive.ubuntu.com trusty Release.gpg
　　Could not resolve 'archive.ubuntu.com'
　　Err http://archive.ubuntu.com trusty-security Release.gpg
　　Could not resolve 'archive.ubuntu.com'
　　Err http://archive.ubuntu.com trusty-updates Release.gpg
　　Could not resolve 'archive.ubuntu.com'
　　Err http://archive.ubuntu.com trusty-proposed Release.gpg
　　Could not resolve 'archive.ubuntu.com'
　　Err http://archive.ubuntu.com trusty-backports Release.gpg
　　Could not resolve 'archive.ubuntu.com'
　　Reading package lists... Done
　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/InRelease
　　

　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-security/InRelease
　　

　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-updates/InRelease
　　

　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-proposed/InRelease
　　

　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-backports/InRelease
　　

　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/Release.gpg  Could not resolve 'archive.ubuntu.com'
　　

　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-security/Release.gpg  Could not resolve 'archive.ubuntu.com'
　　

　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-updates/Release.gpg  Could not resolve 'archive.ubuntu.com'
　　

　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-proposed/Release.gpg  Could not resolve 'archive.ubuntu.com'
　　

　　W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-backports/Release.gpg  Could not resolve 'archive.ubuntu.com'
　　

　　W: Some index files failed to download. They have been ignored, or old ones used instead.
　　
所以在docker里面装nginx的时候也出现问题：
　　root@0cc8c10d217a:~# apt-get install  nginx
　　Reading package lists... Done
　　Building dependency tree
　　Reading state information... Done
　　The following extra packages will be installed:
　　nginx-common nginx-core
　　Suggested packages:
　　fcgiwrap nginx-doc
　　The following NEW packages will be installed:
　　nginx nginx-common nginx-core
　　0 upgraded, 3 newly installed, 0 to remove and 241 not upgraded.
　　Need to get 349 kB of archives.
　　After this operation, 1,300 kB of additional disk space will be used.
　　Do you want to continue? [Y/n] Y
　　WARNING: The following packages cannot be authenticated!
　　nginx-common nginx-core nginx
　　Install these packages without verification? [y/N] Y
　　Err http://archive.ubuntu.com/ubuntu/ trusty-updates/main nginx-common all 1.4.6-1ubuntu3.7
　　Could not resolve 'archive.ubuntu.com'
　　Err http://archive.ubuntu.com/ubuntu/ trusty-updates/main nginx-core amd64 1.4.6-1ubuntu3.7
　　Could not resolve 'archive.ubuntu.com'
　　Err http://archive.ubuntu.com/ubuntu/ trusty-updates/main nginx all 1.4.6-1ubuntu3.7
　　Could not resolve 'archive.ubuntu.com'
　　E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/n/nginx/nginx-common_1.4.6-1ubuntu3.7_all.deb  Could not resolve 'archive.ubuntu.com'
　　

　　E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/n/nginx/nginx-core_1.4.6-1ubuntu3.7_amd64.deb  Could not resolve 'archive.ubuntu.com'
　　

　　E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/n/nginx/nginx_1.4.6-1ubuntu3.7_all.deb  Could not resolve 'archive.ubuntu.com'
　　

　　E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
　　因为刚刚换过apt-get源 ，所以百度了一下知道大概的做法是DNS出现了问题
　　应着重查看以下方面：
cat /etc/resolv.conf查看里面的domain, search和nameserver配置是否正确。
然后一看是DNS出现了问题，所以将nameserver修改成8.8.8.8后，问题得到了解决。