ubuntu apt-get报错

W: GPG 错误：https://download.docker.com/linux/ubuntu xenial InRelease: 由于没有公钥，无法验证下列签名： NO_PUBKEY 7EA0A9C3F273FCD8
W: 仓库 “https://download.docker.com/linux/ubuntu xenial InRelease” 没有数字签名。
N: 无法认证来自该源的数据，所以使用它会带来潜在风险。
N: 参见 apt-secure(8) 手册以了解仓库创建和用户配置方面的细节。
root@ubuntu:/docker# apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 7EA0A9C3F273FCD8

Executing: /tmp/tmp.9KFPG4E1LI/gpg.1.sh --keyserver
keyserver.ubuntu.com
--recv-keys
7EA0A9C3F273FCD8
gpg: requesting key F273FCD8 from hkp server keyserver.ubuntu.com
gpg: key 0EBFCD88: public key "Docker Release (CE deb) " imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
root@ubuntu:/docker# apt-get clean
root@ubuntu:/docker# apt-get update

ubuntu /boot空间不足解决办法
root@ubuntu:/home/ubuntu# df -hl
/dev/sda1                    472M  432M   17M  97% /boot
root@ubuntu:/home/ubuntu# dpkg --get-selections|grep linux
console-setup-linux                install
libselinux1:amd64                install
linux-base                    install
linux-firmware                    install
linux-generic                    install
linux-headers-4.4.0-31                install
linux-headers-4.4.0-31-generic            install
linux-headers-4.4.0-78                install
linux-headers-4.4.0-78-generic            install
linux-headers-4.4.0-79                install
linux-headers-4.4.0-79-generic            install
linux-headers-4.4.0-81                install
linux-headers-4.4.0-81-generic            install
linux-headers-4.4.0-83                install
linux-headers-4.4.0-83-generic            install
linux-headers-4.4.0-87                install
linux-headers-4.4.0-87-generic            install
linux-headers-4.4.0-89                install
linux-headers-4.4.0-89-generic            install
linux-headers-4.4.0-96                install
linux-headers-4.4.0-96-generic            install
linux-headers-4.4.0-97                install
linux-headers-4.4.0-97-generic            install
linux-headers-4.4.0-98                install
linux-headers-4.4.0-98-generic            install
linux-headers-generic                install
linux-image-4.4.0-31-generic            deinstall
linux-image-4.4.0-78-generic            deinstall
linux-image-4.4.0-79-generic            install
linux-image-4.4.0-81-generic            install
linux-image-4.4.0-83-generic            install
linux-image-4.4.0-87-generic            install
linux-image-4.4.0-89-generic            install
linux-image-4.4.0-96-generic            install
linux-image-4.4.0-97-generic            install
linux-image-4.4.0-98-generic            install
linux-image-extra-4.4.0-31-generic        deinstall
linux-image-extra-4.4.0-78-generic        deinstall
linux-image-extra-4.4.0-79-generic        deinstall
linux-image-extra-4.4.0-81-generic        deinstall
linux-image-extra-4.4.0-83-generic        deinstall
linux-image-extra-4.4.0-87-generic        deinstall
linux-image-extra-4.4.0-89-generic        deinstall
linux-image-extra-4.4.0-96-generic        install
linux-image-extra-4.4.0-97-generic        install
linux-image-extra-4.4.0-98-generic        install
linux-image-extra-virtual            install
linux-image-generic                install
linux-libc-dev:amd64                install
util-linux                    install
#linux-后面带image的是旧的内核，可以删除，删除后显示deinstall。
root@ubuntu:/home/ubuntu# apt-get remove linux-image-extra-4.4.0-89-generic
root@ubuntu:/home/ubuntu# df -hl
/dev/sda1                    472M  282M  167M  63% /boot

mdadm: /etc/mdadm/mdadm.conf defines no arrays.
root@ubuntu:/home/ubuntu# /usr/share/mdadm/mkconf > /etc/mdadm/mdadm.conf
root@ubuntu:/home/ubuntu# update-initramfs -u
root@ubuntu:/home/ubuntu# reboot

E: Sub-process /usr/bin/dpkg returned an error code (1)
root@ubuntu:/home/ubuntu# sudo apt-get update --fix-missing
root@ubuntu:/home/ubuntu# sudo apt-get autoremove && sudo apt-get clean && sudo apt-get install -f
或
root@ubuntu:/home/ubuntu# mv /var/lib/dpkg/info /var/lib/dpkg/info.bak
root@ubuntu:/home/ubuntu# mkdir /var/lib/dpkg/info
root@ubuntu:/home/ubuntu# apt-get update
root@ubuntu:/home/ubuntu# apt-get -f install pkg
root@ubuntu:/home/ubuntu# mv /var/lib/dpkg/info/* /var/lib/dpkg/info.bak
root@ubuntu:/home/ubuntu# rm -rf /var/lib/dpkg/info
root@ubuntu:/home/ubuntu# mv /var/lib/dpkg/info.bak /var/lib/dpkg/info