解决apt-get update更新问题：/usr/lib/apt/methods/https could not be found. 和 NO_PUBKEY 7EA0A9C3F273FCD8
问题1：The method driver /usr/lib/apt/methods/https could not be found.
解决办法--执行单独安装命令：apt-get install apt-transport-https
问题2：W: GPG error: https://download.docker.com/linux/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7EA0A9C3F273FCD8
运行如下命令，添加公钥解决: apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 7EA0A9C3F273FCD8
错误信息：
root@2bade87bd9dd:/# apt-get update
Hit:1 http://mirrors.aliyun.com/ubuntu xenial InRelease
Get:2 http://mirrors.aliyun.com/ubuntu xenial-updates InRelease [109 kB]
Get:3 http://mirrors.aliyun.com/ubuntu xenial-backports InRelease [107 kB]
Get:4 http://mirrors.aliyun.com/ubuntu xenial-security InRelease [107 kB]
Get:5 http://mirrors.aliyun.com/ubuntu xenial-updates/main Sources [406 kB]
Get:6 http://mirrors.aliyun.com/ubuntu xenial-updates/restricted Sources [2684 B]
Get:7 http://archive.canonical.com/ubuntu xenial InRelease [11.5 kB]
Get:8 http://mirrors.aliyun.com/ubuntu xenial-updates/multiverse Sources [8995 B]
Hit:9 http://archive.ubuntu.com/ubuntu xenial InRelease
Get:10 http://mirrors.aliyun.com/ubuntu xenial-updates/universe Sources [280 kB]
Get:11 http://mirrors.aliyun.com/ubuntu xenial-updates/main amd64 Packages [1112 kB]
Get:12 http://archive.canonical.com/ubuntu xenial/partner Sources [2408 B]
Get:13 http://mirrors.aliyun.com/ubuntu xenial-updates/restricted amd64 Packages [13.1 kB]
Get:14 http://mirrors.aliyun.com/ubuntu xenial-updates/universe amd64 Packages [889 kB]
Get:15 http://archive.canonical.com/ubuntu xenial/partner amd64 Packages [3248 B]
Get:16 http://mirrors.aliyun.com/ubuntu xenial-updates/multiverse amd64 Packages [18.8 kB]
Get:17 http://mirrors.aliyun.com/ubuntu xenial-backports/main Sources [5103 B]
Get:18 http://mirrors.aliyun.com/ubuntu xenial-backports/universe Sources [7237 B]
Get:19 http://mirrors.aliyun.com/ubuntu xenial-backports/main amd64 Packages [7965 B]
Get:20 http://mirrors.aliyun.com/ubuntu xenial-backports/universe amd64 Packages [8532 B]
Get:21 http://mirrors.aliyun.com/ubuntu xenial-security/main Sources [167 kB]
Get:22 http://mirrors.aliyun.com/ubuntu xenial-security/multiverse Sources [2094 B]
Get:23 http://mirrors.aliyun.com/ubuntu xenial-security/universe Sources [95.4 kB]
Get:24 http://mirrors.aliyun.com/ubuntu xenial-security/main amd64 Packages [723 kB]
Get:25 http://mirrors.aliyun.com/ubuntu xenial-security/universe amd64 Packages [491 kB]
Get:26 http://mirrors.aliyun.com/ubuntu xenial-security/multiverse amd64 Packages [3747 B]
Fetched 4583 kB in 2s (2049 kB/s)
Reading package lists... Done
E: The method driver /usr/lib/apt/methods/https could not be found.
N: Is the package apt-transport-https installed?
E: Failed to fetch https://download.docker.com/linux/ubuntu/dists/xenial/InRelease
E: Some index files failed to download. They have been ignored, or old ones used instead.
root@2bade87bd9dd:/#
解决办法--执行单独安装命令：apt-get install apt-transport-https
root@2bade87bd9dd:/# apt-get install apt-transport-https
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
libllvm5.0
Use 'apt autoremove' to remove it.
The following NEW packages will be installed:
apt-transport-https
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 26.1 kB of archives.
After this operation, 215 kB of additional disk space will be used.
Get:1 http://mirrors.aliyun.com/ubuntu xenial-updates/main amd64 apt-transport-https amd64 1.2.27 [26.1 kB]
Fetched 26.1 kB in 0s (446 kB/s)
debconf: delaying package configuration, since apt-utils is not installed
Selecting previously unselected package apt-transport-https.
(Reading database ... 32433 files and directories currently installed.)
Preparing to unpack .../apt-transport-https_1.2.27_amd64.deb ...
Unpacking apt-transport-https (1.2.27) ...
Setting up apt-transport-https (1.2.27) ...
root@2bade87bd9dd:/#
root@2bade87bd9dd:/# apt-get update
Hit:1 http://mirrors.aliyun.com/ubuntu xenial InRelease
Hit:2 http://mirrors.aliyun.com/ubuntu xenial-updates InRelease
Hit:3 http://mirrors.aliyun.com/ubuntu xenial-backports InRelease
Hit:4 http://mirrors.aliyun.com/ubuntu xenial-security InRelease
Hit:5 http://archive.canonical.com/ubuntu xenial InRelease
Get:6 https://download.docker.com/linux/ubuntu xenial InRelease [66.2 kB]
Ign:6 https://download.docker.com/linux/ubuntu xenial InRelease
Get:7 https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages [4467 B]
Hit:8 http://archive.ubuntu.com/ubuntu xenial InRelease
Fetched 70.7 kB in 3s (19.5 kB/s)
Reading package lists... Done
W: GPG error: https://download.docker.com/linux/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7EA0A9C3F273FCD8
W: The repository 'https://download.docker.com/linux/ubuntu xenial InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
root@2bade87bd9dd:/#
解决办法：
运行如下命令，添加公钥解决:
apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 7EA0A9C3F273FCD8
root@2bade87bd9dd:/# apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 7EA0A9C3F273FCD8
Executing: /tmp/tmp.1aB371lWPG/gpg.1.sh --recv-keys
--keyserver
keyserver.ubuntu.com
7EA0A9C3F273FCD8
gpg: requesting key F273FCD8 from hkp server keyserver.ubuntu.com
gpg: key 0EBFCD88: public key "Docker Release (CE deb)
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
root@2bade87bd9dd:/#
root@2bade87bd9dd:/#
root@2bade87bd9dd:/# apt-get update
Hit:1 http://mirrors.aliyun.com/ubuntu xenial InRelease
Hit:2 http://mirrors.aliyun.com/ubuntu xenial-updates InRelease
Hit:3 http://mirrors.aliyun.com/ubuntu xenial-backports InRelease
Hit:4 http://mirrors.aliyun.com/ubuntu xenial-security InRelease
Hit:5 http://archive.ubuntu.com/ubuntu xenial InRelease
Hit:6 http://archive.canonical.com/ubuntu xenial InRelease
Get:7 https://download.docker.com/linux/ubuntu xenial InRelease [66.2 kB]
Fetched 66.2 kB in 1s (50.8 kB/s)
Reading package lists... Done
root@2bade87bd9dd:/#