运行wget命令下载资源时出现了“HTTP request sent, awaiting response... 404 Not Found”错误，详细如下所示：
# wget https://launchpad.net/ubuntu/+source/linux/4.15.0-45.48/linux_4.15.0.orig.tar.gz
--2022-04-21 09:59:25-- https://launchpad.net/ubuntu/+source/linux/4.15.0-45.48/linux_4.15.0.orig.tar.gz
Resolving launchpad.net (launchpad.net)... 185.125.189.223, 185.125.189.222, 2620:2d:4000:1001::8003, ...
Connecting to launchpad.net (launchpad.net)|185.125.189.223|:443... connected.
HTTP request sent, awaiting response... 404 Not Found
2022-04-21 09:59:26 ERROR 404: Not Found.
开始感觉非常奇怪，因为出现“404 Not Found”是因为资源不存在所导致的，但是https://launchpad.net/ubuntu/+source/linux/4.15.0-45.48/
是能够访问的，如下图所示：
而且在windows下点击“Downloads”下的“linux_4.15.0.orig.tar.gz”链接也是能够成功下载的。这是怎么回事？
后来突然想到，可能是点击链接后实际的下载链接并不是简单的叠加，即“https://launchpad.net/ubuntu/+source/linux/4.15.0-45.48/”后边直接跟“linux_4.15.0.orig.tar.gz”，而是另外有相应的链接。
于是在Windows下右键点击“linux_4.15.0.orig.tar.gz”链接，然后选择“在新标签页中打开链接”，此时可以看到，在新的标签页中的链接果然不是简单的叠加，而是完全不同的链接地址“ https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/linux/4.15.0-45.48/linux_4.15.0.orig.tar.gz”。将wget命令后的地址替换为此地址，这次可以正常下载源码资源了，如下所示：
# wget https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/linux/4.15.0-45.48/linux_4.15.0.orig.tar.gz
--2022-04-21 10:08:36-- https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/linux/4.15.0-45.48/linux_4.15.0.orig.tar.gz
Resolving launchpad.net (launchpad.net)... 185.125.189.223, 185.125.189.222, 2620:2d:4000:1001::8004, ...
Connecting to launchpad.net (launchpad.net)|185.125.189.223|:443... connected.
HTTP request sent, awaiting response... 303 See Other
Location: https://launchpadlibrarian.net/408937941/linux_4.15.0.orig.tar.gz [following]
--2022-04-21 10:08:38-- https://launchpadlibrarian.net/408937941/linux_4.15.0.orig.tar.gz
Resolving launchpadlibrarian.net (launchpadlibrarian.net)... 185.125.189.229, 185.125.189.228, 2620:2d:4000:1001::8007, ...
Connecting to launchpadlibrarian.net (launchpadlibrarian.net)|185.125.189.229|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 157656459 (150M) [application/gzipped-tar]
Saving to: ‘linux_4.15.0.orig.tar.gz’
linux_4.15.0.orig.tar.gz 100%[====================================================================================================================================================================================================>] 150.35M 6.35MB/s in 25s
2022-04-21 10:09:04 (5.94 MB/s) - ‘linux_4.15.0.orig.tar.gz’ saved [157656459/157656459]
