我试过在askubuntu上问这个问题，但还没有find答案 。
我在一台旧机器上安装了Ubuntu Server 32-bit 14.04，并且试图运行sudo apt-get update但后面跟着这个错误信息：
Ign http://security.ubuntu.com trusty-security InRelease Ign http://security.ubuntu.com trusty-security Release.gpg Ign http://security.ubuntu.com trusty-security Release Err http://security.ubuntu.com trusty-security/main Sources Err http://security.ubuntu.com trusty-security/main Sources Err http://security.ubuntu.com trusty-security/main Sources Err http://security.ubuntu.com trusty-security/main Sources Err http://security.ubuntu.com trusty-security/main Sources server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/main/source/Sources server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none E: Some index files failed to download. They have been ignored, or old ones used instead.
我尝试了以下解决scheme：
8.8.8.8和8.8.4.4 sudo update-ca-certificates
Updating certificates in /etc/ssl/certs... 0 added, 0 removed; done. Running hooks in /etc/ca-certificates/update.d.... done. done.
我确定它没有在代理连接下完成。
的sources.list
# # deb cdrom:[Ubuntu-Server 14.04.3 LTS _Trusty Tahr_ - Beta i386 (20150805)]/ trusty main restricted #deb cdrom:[Ubuntu-Server 14.04.3 LTS _Trusty Tahr_ - Beta i386 (20150805)]/ trusty main restricted # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://us.archive.ubuntu.com/ubuntu/ trusty main restricted deb-src http://us.archive.ubuntu.com/ubuntu/ trusty main restricted ## Major bug fix updates produced after the final release of the ## distribution. deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates main restricted deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates main restricted ## NB software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team. Also, please note that software in universe WILL NOT receive any ## review or updates from the Ubuntu security team. deb http://us.archive.ubuntu.com/ubuntu/ trusty universe deb-src http://us.archive.ubuntu.com/ubuntu/ trusty universe deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates universe deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates universe ## NB software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team, and may not be under a free licence. Please satisfy yourself as to ## your rights to use the software. Also, please note that software in ## multiverse WILL NOT receive any review or updates from the Ubuntu ## security team. deb http://us.archive.ubuntu.com/ubuntu/ trusty multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ trusty multiverse deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates multiverse ## NB software from this repository may not have been tested as ## extensively as that contained in the main release, although it includes ## newer versions of some applications which may provide useful features. ## Also, please note that software in backports WILL NOT receive any review ## or updates from the Ubuntu security team. deb http://us.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse deb http://security.ubuntu.com/ubuntu trusty-security main restricted deb-src http://security.ubuntu.com/ubuntu trusty-security main restricted deb http://security.ubuntu.com/ubuntu trusty-security universe deb-src http://security.ubuntu.com/ubuntu trusty-security universe deb http://security.ubuntu.com/ubuntu trusty-security multiverse deb-src http://security.ubuntu.com/ubuntu trusty-security multiverse ## Uncomment the following two lines to add software from Canonical's ## 'partner' repository. ## This software is not part of Ubuntu, but is offered by Canonical and the ## respective vendors as a service to Ubuntu users. # deb http://archive.canonical.com/ubuntu trusty partner # deb-src http://archive.canonical.com/ubuntu trusty partner ## Uncomment the following two lines to add software from Ubuntu's ## 'extras' repository. ## This software is not part of Ubuntu, but is offered by third-party ## developers who want to ship their latest software. # deb http://extras.ubuntu.com/ubuntu trusty main # deb-src http://extras.ubuntu.com/ubuntu trusty main