我有Ubuntu 14.04，如果我这样做：sudo apt-get update
结果是：
Ign http://ftp.debian.org wheezy InRelease
Ign http://ppa.launchpad.net trusty InRelease
Ign http://ppa.launchpad.net trusty InRelease
Get:1 http://security.ubuntu.com trusty-security InRelease [65.9 kB]
Get:2 http://ftp.debian.org wheezy Release.gpg [2,373 B]
Ign http://archive.ubuntu.com trusty InRelease
Ign http://dz.archive.ubuntu.com trusty InRelease
Hit http://ftp.debian.org wheezy Release
Get:3 http://ppa.launchpad.net trusty InRelease [15.4 kB]
Hit http://archive.ubuntu.com trusty Release.gpg
Hit http://dz.archive.ubuntu.com trusty-updates InRelease
Ign http://ftp.debian.org wheezy Release
Ign http://ppa.launchpad.net trusty InRelease
Hit http://ppa.launchpad.net trusty InRelease
Hit http://archive.ubuntu.com trusty Release
Ign http://ftp.debian.org wheezy/main Sources/DiffIndex
Hit http://dz.archive.ubuntu.com trusty-backports InRelease
Hit http://ppa.launchpad.net trusty InRelease
Hit http://ppa.launchpad.net trusty InRelease
Get:4 http://security.ubuntu.com trusty-security/main Sources [110 kB]
Hit http://dz.archive.ubuntu.com trusty Release.gpg
Ign http://ftp.debian.org wheezy/main amd64 Packages/DiffIndex
Hit http://archive.ubuntu.com trusty/universe amd64 Packages
Hit http://ppa.launchpad.net trusty InRelease
Ign http://ftp.debian.org wheezy/main i386 Packages/DiffIndex
Hit http://dz.archive.ubuntu.com trusty-updates/main Sources
Hit http://archive.ubuntu.com trusty/main amd64 Packages
Hit http://ppa.launchpad.net trusty Release.gpg
Hit http://ftp.debian.org wheezy/main Translation-en
Hit http://ppa.launchpad.net trusty Release.gpg
Hit http://dz.archive.ubuntu.com trusty-updates/restricted Sources
Hit http://archive.ubuntu.com trusty/universe i386 Packages
Get:5 http://security.ubuntu.com trusty-security/restricted Sources [4,035 B]
Hit http://ftp.debian.org wheezy/main Sources
Ign http://ppa.launchpad.net trusty/main amd64 Packages/DiffIndex
Hit http://ftp.debian.org wheezy/main amd64 Packages
Ign http://ppa.launchpad.net trusty/main i386 Packages/DiffIndex
Hit http://dz.archive.ubuntu.com trusty-updates/universe Sources
Hit http://archive.ubuntu.com trusty/main i386 Packages
Get:6 http://security.ubuntu.com trusty-security/universe Sources [34.7 kB]
Hit http://ftp.debian.org wheezy/main i386 Packages
Hit http://dz.archive.ubuntu.com trusty-updates/multiverse Sources
Hit http://ppa.launchpad.net trusty/main Translation-en
Get:7 http://security.ubuntu.com trusty-security/multiverse Sources [2,750 B]
Hit http://ppa.launchpad.net trusty/main amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-updates/main amd64 Packages
Hit http://archive.ubuntu.com trusty/main Translation-en
Hit http://ppa.launchpad.net trusty/main i386 Packages
Get:8 http://security.ubuntu.com trusty-security/main amd64 Packages [448 kB]
Ign http://ftp.debian.org wheezy/main Translation-en_US
Hit http://dz.archive.ubuntu.com trusty-updates/restricted amd64 Packages
Hit http://ppa.launchpad.net trusty/main Translation-en
Hit http://ppa.launchpad.net trusty/main amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-updates/universe amd64 Packages
Hit http://archive.ubuntu.com trusty/universe Translation-en
Hit http://ppa.launchpad.net trusty/main i386 Packages
Hit http://dz.archive.ubuntu.com trusty-updates/multiverse amd64 Packages
Hit http://ppa.launchpad.net trusty/main Translation-en
Hit http://dz.archive.ubuntu.com trusty-updates/main i386 Packages
Hit http://ppa.launchpad.net trusty/main amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-updates/restricted i386 Packages
Hit http://ppa.launchpad.net trusty/main i386 Packages
Hit http://ppa.launchpad.net trusty/main Translation-en
Hit http://dz.archive.ubuntu.com trusty-updates/universe i386 Packages
Hit http://ppa.launchpad.net trusty/main amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-updates/multiverse i386 Packages
Hit http://ppa.launchpad.net trusty/main i386 Packages
Hit http://ppa.launchpad.net trusty/main Translation-en
Hit http://dz.archive.ubuntu.com trusty-updates/main Translation-en
Hit http://ppa.launchpad.net trusty Release
Hit http://dz.archive.ubuntu.com trusty-updates/multiverse Translation-en
Hit http://ppa.launchpad.net trusty Release
Hit http://ppa.launchpad.net trusty/main amd64 Packages
Hit http://ppa.launchpad.net trusty/main i386 Packages
Hit http://dz.archive.ubuntu.com trusty-updates/restricted Translation-en
Hit http://ppa.launchpad.net trusty/main amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-updates/universe Translation-en
Hit http://ppa.launchpad.net trusty/main i386 Packages
Hit http://dz.archive.ubuntu.com trusty-backports/main Sources
Hit http://dz.archive.ubuntu.com trusty-backports/restricted Sources
Hit http://ppa.launchpad.net trusty/main amd64 Packages
Ign http://archive.ubuntu.com trusty/main Translation-en_US
Hit http://ppa.launchpad.net trusty/main i386 Packages
Hit http://dz.archive.ubuntu.com trusty-backports/universe Sources
Ign http://archive.ubuntu.com trusty/universe Translation-en_US
Hit http://dz.archive.ubuntu.com trusty-backports/multiverse Sources
Hit http://dz.archive.ubuntu.com trusty-backports/main amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-backports/restricted amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-backports/universe amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-backports/multiverse amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-backports/main i386 Packages
Hit http://dz.archive.ubuntu.com trusty-backports/restricted i386 Packages
Hit http://dz.archive.ubuntu.com trusty-backports/universe i386 Packages
Get:9 http://security.ubuntu.com trusty-security/restricted amd64 Packages [13.0 kB]
Hit http://dz.archive.ubuntu.com trusty-backports/multiverse i386 Packages
Ign http://ppa.launchpad.net trusty/main Translation-en_US
Ign http://dl.google.com stable InRelease
Get:10 http://security.ubuntu.com trusty-security/universe amd64 Packages [126 kB]
Hit http://dz.archive.ubuntu.com trusty-backports/main Translation-en
Hit http://dl.google.com stable Release.gpg
Hit http://dz.archive.ubuntu.com trusty-backports/multiverse Translation-en
Hit http://dl.google.com stable Release
Hit http://dl.google.com stable/main amd64 Packages
Hit http://dz.archive.ubuntu.com trusty-backports/restricted Translation-en
Ign http://ppa.launchpad.net trusty/main Translation-en_US
Hit http://dl.google.com stable/main i386 Packages
Ign http://ppa.launchpad.net trusty/main Translation-en
Ign http://ppa.launchpad.net trusty/main Translation-en_US
Ign http://ppa.launchpad.net trusty/main Translation-en
Hit http://dz.archive.ubuntu.com trusty-backports/universe Translation-en
Hit http://dz.archive.ubuntu.com trusty Release
Hit http://dz.archive.ubuntu.com trusty/main Sources
Get:11 http://security.ubuntu.com trusty-security/multiverse amd64 Packages [4,991 B]
Hit http://dz.archive.ubuntu.com trusty/restricted Sources
Get:12 http://security.ubuntu.com trusty-security/main i386 Packages [422 kB]
Hit http://dz.archive.ubuntu.com trusty/universe Sources
Hit http://dz.archive.ubuntu.com trusty/multiverse Sources
Hit http://dz.archive.ubuntu.com trusty/main amd64 Packages
Hit http://dz.archive.ubuntu.com trusty/restricted amd64 Packages
Hit http://dz.archive.ubuntu.com trusty/universe amd64 Packages
Hit http://dz.archive.ubuntu.com trusty/multiverse amd64 Packages
Hit http://dz.archive.ubuntu.com trusty/main i386 Packages
Hit http://dz.archive.ubuntu.com trusty/restricted i386 Packages
Hit http://dz.archive.ubuntu.com trusty/universe i386 Packages
Hit http://dz.archive.ubuntu.com trusty/multiverse i386 Packages
Hit http://dz.archive.ubuntu.com trusty/main Translation-en
Hit http://dz.archive.ubuntu.com trusty/multiverse Translation-en
Hit http://dz.archive.ubuntu.com trusty/restricted Translation-en
Ign http://dl.google.com stable/main Translation-en_US
Hit http://dz.archive.ubuntu.com trusty/universe Translation-en
Ign http://dl.google.com stable/main Translation-en
Get:13 http://security.ubuntu.com trusty-security/restricted i386 Packages [12.7 kB]
Get:14 http://security.ubuntu.com trusty-security/universe i386 Packages [126 kB]
Ign http://dz.archive.ubuntu.com trusty/main Translation-en_US
Ign http://dz.archive.ubuntu.com trusty/multiverse Translation-en_US
Ign http://dz.archive.ubuntu.com trusty/restricted Translation-en_US
Get:15 http://security.ubuntu.com trusty-security/multiverse i386 Packages [5,175 B]
Ign http://dz.archive.ubuntu.com trusty/universe Translation-en_US
Hit http://security.ubuntu.com trusty-security/main Translation-en
Hit http://security.ubuntu.com trusty-security/multiverse Translation-en
Hit http://security.ubuntu.com trusty-security/restricted Translation-en
Hit http://security.ubuntu.com trusty-security/universe Translation-en
Fetched 1,392 kB in 12s (115 kB/s)
Reading package lists... Done
W: GPG error: http://ftp.debian.org wheezy Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010 NO_PUBKEY 6FB2A1C265FFB764
W: GPG error: http://ppa.launchpad.net trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B5B116B72D0F61F0
有什么问题？以及如何解决这个问题？ 问题是：
W：GPG错误：http://ftp.debian.org wheezy发布：以下内容 签名无法验证，因为公钥不是 可用：NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010 NO_PUBKEY 6FB2A1C265FFB764 W：GPG错误：http://ppa.launchpad.net可靠InRelease：以下签名无法验证，因为公钥是 不可用：NO_PUBKEY B5B116B72D0F61F0
答案 0 :(得分：1)
尝试：sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys <missing_key>