sudo apt-get update 失敗並出現以下錯誤：
Err:3 http://localrepo.local/ubuntu xenial/main amd64 Packages
Connection failed
Ign:4 http://localrepo.local/ubuntu xenial/main i386 Packages
Ign:5 http://localrepo.local/ubuntu xenial/main all Packages
Ign:6 http://localrepo.local/ubuntu xenial/main Translation-en_GB
Ign:7 http://localrepo.local/ubuntu xenial/main Translation-en
Ign:8 http://localrepo.local/ubuntu xenial/restricted amd64 Packages
Ign:9 http://localrepo.local/ubuntu xenial/restricted i386 Packages
Ign:10 http://localrepo.local/ubuntu xenial/restricted all Packages
Ign:11 http://localrepo.local/ubuntu xenial/restricted Translation-en_GB
Ign:12 http://localrepo.local/ubuntu xenial/restricted Translation-en
Reading package lists... Done
W: The repository 'http://localrepo.local/ubuntu xenial Release' does not have a Release file.
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.
E: Failed to fetch http://localrepo.local/ubuntu/dists/xenial/main/binary-amd64/Packages Connection failed
E: Some index files failed to download. They have been ignored, or old ones used instead.
看來apt-get無法下載該文件，但可以透過wget下載：
$ wget http://localrepo.local/ubuntu/dists/xenial/main/binary-amd64/Packages
--2017-10-04 09:31:18-- http://localrepo.local/ubuntu/dists/xenial/main/binary-amd64/Packages
Resolving localrepo.local(localrepo.local)... 10.38.101.107
Connecting to localrepo.local (localrepo.local)|10.38.101.107|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 7228243 (6.9M)
Saving to: ‘Packages’
Packages 100%[===============================================================================================================================>] 6.89M 1.28MB/s in 5.6s
2017-10-04 09:31:29 (1.23 MB/s) - ‘Packages’ saved [7228243/7228243]
知道問題出在哪裡嗎？
編輯：提到的問題和答案是關於一個不可用的特定儲存庫，而提問者收到 404 錯誤。就我而言，存儲庫可用且沒有 404 錯誤。
另外，以下內容不是錯誤，而是警告和通知：
W: The repository 'http://localrepo.local/ubuntu xenial Release' does not have a Release file.
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.
錯誤：
Err:3 http://localrepo.local/ubuntu xenial/main amd64 Packages
Connection failed
和：
E: Failed to fetch http://localrepo.local/ubuntu/dists/xenial/main/binary-amd64/Packages Connection failed
E: Some index files failed to download. They have been ignored, or old ones used instead.