当我登录到我的docker-machine（由 digitalocean 托管）时，我看到以下消息：
62 packages can be updated.
28 updates are security updates.
但每当我尝试运行时apt-get update，都会出现以下情况：
root@alexus:~# apt-get update
Ign http://security.ubuntu.com trusty-security InRelease
Hit http://security.ubuntu.com trusty-security Release.gpg
Hit http://security.ubuntu.com trusty-security Release
Hit http://security.ubuntu.com trusty-security/main Sources
Hit http://security.ubuntu.com trusty-security/universe Sources
Hit http://security.ubuntu.com trusty-security/main amd64 Packages
Hit http://security.ubuntu.com trusty-security/universe amd64 Packages
Hit http://security.ubuntu.com trusty-security/main i386 Packages
Hit http://security.ubuntu.com trusty-security/universe i386 Packages
Hit http://security.ubuntu.com trusty-security/main Translation-en
Hit http://security.ubuntu.com trusty-security/universe Translation-en
Ign http://mirrors.digitalocean.com trusty InRelease
Ign http://mirrors.digitalocean.com trusty-updates InRelease
Hit http://mirrors.digitalocean.com trusty Release.gpg
Get:1 https://apt.dockerproject.org ubuntu-trusty InRelease
Ign https://apt.dockerproject.org ubuntu-trusty InRelease
Hit https://apt.dockerproject.org ubuntu-trusty Release.gpg
Hit https://apt.dockerproject.org ubuntu-trusty Release
Hit https://apt.dockerproject.org ubuntu-trusty/main amd64 Packages
Hit https://apt.dockerproject.org ubuntu-trusty/main i386 Packages
Get:2 http://mirrors.digitalocean.com trusty-updates Release.gpg [933 B]
Get:3 https://apt.dockerproject.org ubuntu-trusty/main Translation-en_US
Hit http://mirrors.digitalocean.com trusty Release
Ign https://apt.dockerproject.org ubuntu-trusty/main Translation-en_US
Ign https://apt.dockerproject.org ubuntu-trusty/main Translation-en
Get:4 http://mirrors.digitalocean.com trusty-updates Release [63.5 kB]
Hit http://mirrors.digitalocean.com trusty/main Sources
Hit http://mirrors.digitalocean.com trusty/universe Sources
Hit http://mirrors.digitalocean.com trusty/main amd64 Packages
Hit http://mirrors.digitalocean.com trusty/universe amd64 Packages
Hit http://mirrors.digitalocean.com trusty/main i386 Packages
Hit http://mirrors.digitalocean.com trusty/universe i386 Packages
Hit http://mirrors.digitalocean.com trusty/main Translation-en
Hit http://mirrors.digitalocean.com trusty/universe Translation-en
Get:5 http://mirrors.digitalocean.com trusty-updates/main Sources [237 kB]
Get:6 http://mirrors.digitalocean.com trusty-updates/universe Sources [139 kB]
Get:7 http://mirrors.digitalocean.com trusty-updates/main amd64 Packages [627 kB]
Get:8 http://mirrors.digitalocean.com trusty-updates/universe amd64 Packages [320 kB]
Get:9 http://mirrors.digitalocean.com trusty-updates/main i386 Packages [608 kB]
Get:10 http://mirrors.digitalocean.com trusty-updates/universe i386 Packages [320 kB]
Hit http://mirrors.digitalocean.com trusty-updates/main Translation-en
Hit http://mirrors.digitalocean.com trusty-updates/universe Translation-en
Ign http://mirrors.digitalocean.com trusty/main Translation-en_US
Ign http://mirrors.digitalocean.com trusty/universe Translation-en_US
Fetched 2,316 kB in 4s (513 kB/s)
Reading package lists... Done
root@alexus:~#
我的系统的操作系统和内核：
root@alexus:~# cat /etc/issue.net
Ubuntu 14.04.3 LTS
root@alexus:~# uname -a
Linux alexus 3.13.0-57-generic #95-Ubuntu SMP Fri Jun 19 09:28:15 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
root@alexus:~#
如何更新我的系统？
答案1
apt-get update运行后，将更新可用软件包列表。然后，要执行更新，请运行sudo apt-get upgrade。我使用 sudo 命令，这样就无需以 root 身份登录即可执行更新。
还有一些更新不会使用此命令升级，sudo apt-get dist-upgrade必须对这些更新使用该命令。