錯誤：
W: Failed to fetch http://ppa.launchpad.net/sergiomejia666/xresprobe/ubuntu/dists/trusty/main/binary-amd64/Packages 404 Not Found [IP: 91.189.95.83 80]
W: Failed to fetch http://ppa.launchpad.net/sergiomejia666/xresprobe/ubuntu/dists/trusty/main/binary-i386/Packages 404 Not Found [IP: 91.189.95.83 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
解決：
1、查詢失敗的記錄
sudo apt-get update | grep "Failed"
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2、舊的版本上添加的一些第三方PPA倉庫不再受新版本的支持，移除掉
sudo add-apt-repository --remove ppa:sergiomejia666/xresprobe
3、重新進行更新
sudo apt-get update