實例：
root@mfus1006:~# apt-get update
Hit http://security.debian.org wheezy/updates Release.gpg
Hit http://security.debian.org wheezy/updates Release
Hit http://ftp.debian.org wheezy Release.gpg
Hit http://security.debian.org wheezy/updates/main i386 Packages
Hit http://security.debian.org wheezy/updates/contrib i386 Packages
Hit http://ftp.debian.org wheezy Release
Hit http://security.debian.org wheezy/updates/non-free i386 Packages
Hit http://security.debian.org wheezy/updates/contrib Translation-en
Hit http://ftp.debian.org wheezy/main i386 Packages
Hit http://security.debian.org wheezy/updates/main Translation-en
Hit http://ftp.debian.org wheezy/contrib i386 Packages
Hit http://security.debian.org wheezy/updates/non-free Translation-en
Hit http://ftp.debian.org wheezy/non-free i386 Packages
Hit http://ftp.debian.org wheezy/contrib Translation-en
Hit http://ftp.debian.org wheezy/main Translation-en
Hit http://ftp.debian.org wheezy/non-free Translation-en
Reading package lists... Done
W: There is no public key available for the following key IDs:
9D6D8F6BC857C906
W: There is no public key available for the following key IDs:
7638D0442B90D010
解決public key的問題的命令
命令一：
apt-get install debian-keyring debian-archive-keyring
apt-get install debian-keyring debian-archive-keyring
命令二：
apt-key update
apt-key update
實例：
命令一：
root@mfus1006:~# apt-get install debian-keyring debian-archive-keyring
Reading package lists... Done
Building dependency tree
Reading state information... Done
debian-keyring is already the newest version.
The following packages will be upgraded:
debian-archive-keyring
1 upgraded, 0 newly installed, 0 to remove and 79 not upgraded.
Need to get 60.7 kB of archives.
After this operation, 26.6 kB of additional disk space will be used.
Do you want to continue [Y/n]? y 這里需要回答 y 確定
Get:1 http://ftp.debian.org/debian/ wheezy/main debian-archive-keyring all 2014.3~deb7u1 [60.7 kB]
Fetched 60.7 kB in 0s (101 kB/s)
(Reading database ... 30582 files and directories currently installed.)
Preparing to replace debian-archive-keyring 2012.4 (using .../debian-archive-keyring_2014.3~deb7u1_all.deb) ...
Unpacking replacement debian-archive-keyring ...
Setting up debian-archive-keyring (2014.3~deb7u1) ...
命令二：
命令二：
root@mfus1006:~# apt-key update
gpg: key B98321F9: "Squeeze Stable Release Key <debian-release@lists.debian.org>" not changed
gpg: key 473041FA: "Debian Archive Automatic Signing Key (6.0/squeeze) <ftpmaster@debian.org>" not changed
gpg: key 65FFB764: "Wheezy Stable Release Key <debian-release@lists.debian.org>" not changed
gpg: key 46925553: "Debian Archive Automatic Signing Key (7.0/wheezy) <ftpmaster@debian.org>" not changed
gpg: key 518E17E1: "Jessie Stable Release Key <debian-release@lists.debian.org>" not changed
gpg: key 2B90D010: "Debian Archive Automatic Signing Key (8/jessie) <ftpmaster@debian.org>" not changed
gpg: key C857C906: "Debian Security Archive Automatic Signing Key (8/jessie) <ftpmaster@debian.org>" not changed
gpg: Total number processed: 7
gpg: unchanged: 7
測試再次升級：
測試再次升級：
root@mfus1006:~# apt-get update
Hit http://ftp.debian.org wheezy Release.gpg
Hit http://security.debian.org wheezy/updates Release.gpg
Hit http://ftp.debian.org wheezy Release
Hit http://security.debian.org wheezy/updates Release
Hit http://security.debian.org wheezy/updates/main i386 Packages
Hit http://ftp.debian.org wheezy/main i386 Packages
Hit http://security.debian.org wheezy/updates/contrib i386 Packages
Hit http://security.debian.org wheezy/updates/non-free i386 Packages
Hit http://ftp.debian.org wheezy/contrib i386 Packages
Hit http://security.debian.org wheezy/updates/contrib Translation-en
Hit http://security.debian.org wheezy/updates/main Translation-en
Hit http://ftp.debian.org wheezy/non-free i386 Packages
Hit http://security.debian.org wheezy/updates/non-free Translation-en
Hit http://ftp.debian.org wheezy/contrib Translation-en
Hit http://ftp.debian.org wheezy/main Translation-en
Hit http://ftp.debian.org wheezy/non-free Translation-en
Reading package lists... Done
