问题

sudo add-apt-repository ppa:ubuntugis/ppa
sudo apt-get update

haifeng@X220i:~$ sudo add-apt-repository ppa:ubuntugis/ppa
[sudo] haifeng 的密码：
 Official stable UbuntuGIS packages.

 更多信息： https://launchpad.net/~ubuntugis/+archive/ubuntu/ppa
按回车继续或者 Ctrl+c 取消添加

gpg: 钥匙环‘/tmp/tmpncw1rcwr/secring.gpg’已建立
gpg: 钥匙环‘/tmp/tmpncw1rcwr/pubring.gpg’已建立
gpg: 下载密钥‘314DF160’，从 hkp 服务器 keyserver.ubuntu.com
gpg: /tmp/tmpncw1rcwr/trustdb.gpg：建立了信任度数据库
gpg: 密钥 314DF160：公钥“Launchpad ubuntugis-stable”已导入
gpg: 合计被处理的数量：1
gpg:               已导入：1  (RSA: 1)
OK
haifeng@X220i:~$

haifeng@X220i:~$ sudo apt-get update

命中:1 http://cn.archive.ubuntu.com/ubuntu xenial InRelease
命中:2 http://cn.archive.ubuntu.com/ubuntu xenial-updates InRelease            
命中:3 http://cn.archive.ubuntu.com/ubuntu xenial-backports InRelease          
获取:4 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]    
获取:5 http://ppa.launchpad.net/ubuntugis/ppa/ubuntu xenial InRelease [23.8 kB]
获取:6 http://security.ubuntu.com/ubuntu xenial-security/main amd64 DEP-11 Metadata [60.2 kB]
获取:7 http://ppa.launchpad.net/ubuntugis/ppa/ubuntu xenial/main amd64 Packages [42.9 kB]
获取:8 http://security.ubuntu.com/ubuntu xenial-security/main DEP-11 64x64 Icons [57.6 kB]
获取:9 http://security.ubuntu.com/ubuntu xenial-security/universe amd64 DEP-11 Metadata [49.2 kB]
获取:10 http://security.ubuntu.com/ubuntu xenial-security/universe DEP-11 64x64 Icons [69.8 kB]
获取:11 http://ppa.launchpad.net/ubuntugis/ppa/ubuntu xenial/main i386 Packages [43.0 kB]
获取:12 http://ppa.launchpad.net/ubuntugis/ppa/ubuntu xenial/main Translation-en [17.4 kB]
已下载 466 kB，耗时 9秒 (48.5 kB/s)                                            
正在读取软件包列表... 完成
haifeng@X220i:~$

haifeng@X220i:/etc/apt/sources.list.d$ ls
fcitx-team-ubuntu-nightly-xenial.list  ubuntugis-ubuntu-ppa-xenial.list.save
ubuntugis-ubuntu-ppa-xenial.list

References:

https://launchpad.net/~ubuntugis/+archive/ubuntu/ppa

如何删除PPA

sudo add-apt-repository --remove ppa:PPA_Name/ppa

实验过程

haifeng@X220i:~$ sudo add-apt-repository --remove ppa:fcitx-team/nightly
 Experimental releases of Fcitx, use with caution.
 更多信息： https://launchpad.net/~fcitx-team/+archive/ubuntu/nightly
按 [ENTER] 可继续操作，按 ctrl-c 可取消其删除操作

haifeng@X220i:~$

References:

https://itsfoss.com/how-to-remove-or-delete-ppas-quick-tip/