几天前，当我尝试“更新”和“升级”时，我开始面临这个突然的问题，这是关于 apt-repository 中包索引文件损坏的问题，但我一直无法弄清楚；在这里，以下是命令行上的输出：
$ sudo apt-get upgrade
[sudo] password for adarshc:
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
linux-headers-generic-lts-raring linux-image-generic-lts-raring
The following packages will be upgraded:
accountsservice apt apt-transport-https apt-utils avahi-autoipd avahi-daemon avahi-utils base-files bc bind9-host chromium-browser
chromium-browser-l10n chromium-codecs-ffmpeg consolekit dc dnsutils duplicity firefox firefox-locale-en flashplugin-installer fonts-opensymbol gdm
gir1.2-accountsservice-1.0 gir1.2-appindicator3-0.1 gir1.2-gtk-3.0 gnome-control-center gnome-control-center-data gnome-desktop3-data
gnome-tweak-tool gnupg gpgv grub-common grub-pc grub-pc-bin grub2-common iproute landscape-client-ui-install language-pack-en
language-pack-en-base language-pack-gnome-en language-pack-gnome-en-base libaccountsservice0 libappindicator1 …