tejesh@tejesh-Inspiron-3542:~$ sudo apt-get update
Ign http:// extras.ubuntu.com trusty InRelease
Ign http:// dl.google.com stable InRelease
Hit http:// dl.google.com stable Release.gpg
Ign http:// ppa.launchpad.net trusty InRelease
Hit http:// extras.ubuntu.com trusty Release.gpg
Hit http:// archive.canonical.com trusty InRelease
Hit http:// dl.google.com stable Release
Ign http:// ppa.launchpad.net trusty InRelease
Hit http:// extras.ubuntu.com trusty Release
Hit http:// dl.google.com stable/main amd64 Packages
Hit http:// archive.canonical.com trusty/partner Sources
Hit http:// dl.google.com stable/main i386 Packages
Ign http:// ppa.launchpad.net trusty InRelease
Hit http:// extras.ubuntu.com trusty/main Sources
Hit http:// archive.canonical.com trusty/partner amd64 Packages
Ign http:// ppa.launchpad.net trusty InRelease
Hit http:// extras.ubuntu.com trusty/main amd64 Packages
Hit http:// archive.canonical.com trusty/partner i386 Packages
Ign http:// ppa.launchpad.net trusty InRelease
Hit http:// extras.ubuntu.com trusty/main i386 Packages
Hit http:// archive.canonical.com trusty/partner Translation-en
Hit http:// ppa.launchpad.net trusty InRelease
Ign http:// ppa.launchpad.net trusty InRelease
Ign http:// dl.google.com stable/main Translation-en_IN
Ign http:// dl.google.com stable/main Translation-en
Ign http:// ppa.launchpad.net trusty InRelease
Ign http:// ppa.launchpad.net trusty InRelease
Ign http:// ppa.launchpad.net trusty InRelease
Ign http:// ppa.launchpad.net trusty InRelease
Hit http:// ppa.launchpad.net trusty Release.gpg
Hit http:// ppa.launchpad.net trusty Release.gpg
Hit http:// ppa.launchpad.net trusty Release.gpg
Ign http:// extras.ubuntu.com trusty/main Translation-en_IN
Hit http:// ppa.launchpad.net trusty Release.gpg
Ign http:// extras.ubuntu.com trusty/main Translation-en
Hit http:// ppa.launchpad.net trusty Release.gpg
Hit http:// ppa.launchpad.net trusty/main amd64 Packages
Hit http:// ppa.launchpad.net trusty/main i386 Packages
Hit http:// ppa.launchpad.net trusty/main Translation-en
Hit http:// ppa.launchpad.net trusty Release.gpg
Hit http:// ppa.launchpad.net trusty Release.gpg
Ign http:// ppa.launchpad.net trusty Release.gpg
Hit http:// ppa.launchpad.net trusty Release.gpg
Hit http:// ppa.launchpad.net trusty Release.gpg
Hit http:// ppa.launchpad.net trusty Release
Hit http:// ppa.launchpad.net trusty Release
Hit http:// ppa.launchpad.net trusty Release
Hit http:// ppa.launchpad.net trusty Release
Hit http:// ppa.launchpad.net trusty Release
Hit http:// ppa.launchpad.net trusty Release
Hit http:// ppa.launchpad.net trusty Release
Ign http:// ppa.launchpad.net trusty Release
Hit http:// ppa.launchpad.net trusty Release
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:// ppa.launchpad.net trusty/main Translation-en
Hit http:// ppa.launchpad.net trusty/main amd64 Packages
Hit http:// ppa.launchpad.net trusty/main i386 Packages
Hit http:// ppa.launchpad.net trusty/main amd64 Packages
Hit http:// ppa.launchpad.net trusty/main i386 Packages
Hit http:// ppa.launchpad.net trusty/main amd64 Packages
Hit http:// ppa.launchpad.net trusty/main i386 Packages
Hit http:// ppa.launchpad.net trusty/main Translation-en
Hit http:// ppa.launchpad.net trusty/main amd64 Packages
Hit http:// ppa.launchpad.net trusty/main i386 Packages
Hit http:// ppa.launchpad.net trusty/main Translation-en
Hit http:// ppa.launchpad.net trusty/main amd64 Packages
Hit http:// ppa.launchpad.net trusty/main i386 Packages
Hit http:// ppa.launchpad.net trusty/main Translation-en
Hit http:// ppa.launchpad.net trusty/main amd64 Packages
Hit http:// ppa.launchpad.net trusty/main i386 Packages
Hit http:// ppa.launchpad.net trusty/main amd64 Packages
Hit http:// ppa.launchpad.net trusty/main i386 Packages
Hit http:// ppa.launchpad.net trusty/main Translation-en
Hit http:// ppa.launchpad.net trusty/main amd64 Packages
Hit http:// ppa.launchpad.net trusty/main i386 Packages
Hit http:// ppa.launchpad.net trusty/main Translation-en
Ign http:// ppa.launchpad.net trusty/main Translation-en_IN
Ign http:// ppa.launchpad.net trusty/main Translation-en
Ign http:// ppa.launchpad.net trusty/main Translation-en_IN
Ign http:// ppa.launchpad.net trusty/main Translation-en
Ign http:// ppa.launchpad.net trusty/main Translation-en_IN
Ign http:// ppa.launchpad.net trusty/main Translation-en
Err http:// ppa.launchpad.net trusty/main amd64 Packages
404 Not Found
Err http:// ppa.launchpad.net trusty/main i386 Packages
404 Not Found
Ign http:// ppa.launchpad.net trusty/main Translation-en_IN
Ign http:// ppa.launchpad.net trusty/main Translation-en
Ign http:// archive.ubuntu.com trusty InRelease
Hit http:// archive.ubuntu.com trusty-updates InRelease
Hit http:// archive.ubuntu.com trusty-backports InRelease
Hit http:// archive.ubuntu.com trusty-security InRelease
Ign http:// archive.ubuntu.com trusty Release.gpg
Get:1 http:// archive.ubuntu.com trusty-updates/main Sources [237 kB]
Get:2 http:// archive.ubuntu.com trusty-updates/universe Sources [140 kB]
Get:3 http:// archive.ubuntu.com trusty-updates/multiverse Sources [5,144 B]
Get:4 http:// archive.ubuntu.com trusty-updates/main amd64 Packages [627 kB]
Get:5 http:// archive.ubuntu.com trusty-updates/restricted amd64 Packages [15.4 kB]
Get:6 http:// archive.ubuntu.com trusty-updates/universe amd64 Packages [320 kB]
Get:7 http:// archive.ubuntu.com trusty-updates/multiverse amd64 Packages [11.9 kB]
Get:8 http:// archive.ubuntu.com trusty-updates/main i386 Packages [608 kB]
Get:9 http:// archive.ubuntu.com trusty-updates/restricted i386 Packages [15.1 kB]
Get:10 http:// archive.ubuntu.com trusty-updates/universe i386 Packages [321 kB]
Get:11 http:// archive.ubuntu.com trusty-updates/multiverse i386 Packages [12.1 kB]
Get:12 http:// archive.ubuntu.com trusty-updates/main Translation-en [304 kB]
100% [Waiting for headers]
答案1
该apt-get update过程已完成，最后几行如下：
Fetched 15.2 MB in 47min 46s (5,304 B/s)
W: Failed to fetch ppa .launchpad.net/picaso/octave/ubuntu/dists/trusty/main/… 404 Not Found
W: Failed to fetch ppa .launchpad.net/picaso/octave/ubuntu/dists/trusty/main/… 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
tejesh@tejesh-Inspiron-3542:~$
当您获得此信息后，打开应用程序软件和更新，然后从其他选项卡中将其从列表中删除：
ppa .launchpad.net/picaso/octave/ubuntu/dists/trusty/main