即使不是发布日，从主 Ubuntu 存档下载也很慢，我如何让 apt-get 自动使用离我很近的镜像？
我正在尝试在 Xubuntu 12.04 VM（内核版本 3.2.0-23-generic）中挂载一个 hfsplus 文件系统，但是当我输入mount -o remount,rw /dev/sdb3命令行时它返回not mounted or bad option. 任何帮助，将不胜感激。
当我升级时，它会卡在这里：
user@plato:~# sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
bind9-host coreutils cpio curl dnsutils libbind9-90 libc-bin libc-dev-bin
libc6 libc6-dev libcgmanager0 libcurl3 libcurl3-gnutls libdns100
libdrm-intel1 libdrm-nouveau2 libdrm-radeon1 libdrm2 libisc95 libisccc90
libisccfg90 libjasper1 liblwres90 libplymouth2 libsepol1 libssl-dev
libssl-doc libssl1.0.0 linux-libc-dev mime-support multiarch-support ntp
ntpdate openssl plymouth plymouth-theme-ubuntu-text python3-distupgrade
ubuntu-release-upgrader-core unzip
39 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 16.0 …我可以使用移动宽带通过 Firefox 访问互联网，但是当我想从终端安装任何软件包或执行“apt-get update”命令时，出现以下错误：
got 'NODATA' (does the network require authentication?)
apt-get 更新输出：
Get:1 extras.ubuntu.com trusty InRelease [213 B] 98% [1 InRelease gpgv 213 B] [Connecting to archive.ubuntu.com]
Splitting up /var/lib/apt/lists/partial/extras.ubuntu.com_ubuntu_dists_trusty_InRelease into data
Ign extras.ubuntu.com trusty InRelease E: GPG error: extras.ubuntu.com trusty InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)
`cat /var/lib/apt/lists/partial/extras.ubuntu.com_ubuntu_dists_trusty_InRelease 的输出
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>404</title> <meta http-equiv="Cache-Control" content="no-cache"/> </head> <body> <p> Not Found </p> </body> </html>
wget 的输出： …
apt ×3
14.04 ×1
command-line ×1
filesystem ×1
mirrors ×1
mount ×1
repository ×1
updates ×1
upgrade ×1