我看到有几个人问过这个问题，但我也遇到了同样的问题。这是 apt-get update 的输出。
desktop:/etc/apt$ sudo apt-get update
Hit:3 http://packages.ros.org/ros/ubuntu bionic InRelease
Hit:5 http://ports.ubuntu.com/ubuntu-ports bionic-security InRelease
Get:1 http://us.archive.ubuntu.com/ubuntu bionic InRelease [242 kB]
Hit:6 https://repo.download.nvidia.com/jetson/common r32.4 InRelease
Hit:7 http://ppa.launchpad.net/slightech/mynt-eye-s-sdk/ubuntu bionic InRelease
Hit:8 http://archive.canonical.com/ubuntu bionic InRelease
Hit:9 https://storage.googleapis.com/bazel-apt stable InRelease
Hit:10 https://repo.download.nvidia.com/jetson/t194 r32.4 InRelease
Get:2 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:4 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Ign:11 http://us.archive.ubuntu.com/ubuntu bionic/main arm64 Packages
Get:12 http://us.archive.ubuntu.com/ubuntu bionic/main Translation-en [516 kB]
Get:13 http://us.archive.ubuntu.com/ubuntu bionic/main arm64 DEP-11 Metadata [472 kB]
Get:14 http://us.archive.ubuntu.com/ubuntu bionic/main DEP-11 48x48 Icons [118 kB]
Get:15 http://us.archive.ubuntu.com/ubuntu bionic/main DEP-11 64x64 Icons [245 kB]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages [664 B]
Ign:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages
Ign:38 http://us.archive.ubuntu.com/ubuntu bionic/universe arm64 Packages
Ign:39 http://us.archive.ubuntu.com/ubuntu bionic/multiverse arm64 Packages
Ign:11 http://us.archive.ubuntu.com/ubuntu bionic/main arm64 Packages
Ign:40 http://us.archive.ubuntu.com/ubuntu bionic-updates/main arm64 Packages
Ign:41 http://us.archive.ubuntu.com/ubuntu bionic-updates/restricted arm64 Packages
Ign:42 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe arm64 Packages
Ign:43 http://us.archive.ubuntu.com/ubuntu bionic-updates/multiverse arm64 Packages
Ign:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages
Ign:38 http://us.archive.ubuntu.com/ubuntu bionic/universe arm64 Packages
Ign:39 http://us.archive.ubuntu.com/ubuntu bionic/multiverse arm64 Packages
Ign:11 http://us.archive.ubuntu.com/ubuntu bionic/main arm64 Packages
Ign:40 http://us.archive.ubuntu.com/ubuntu bionic-updates/main arm64 Packages
Ign:41 http://us.archive.ubuntu.com/ubuntu bionic-updates/restricted arm64 Packages
Ign:42 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe arm64 Packages
Ign:43 http://us.archive.ubuntu.com/ubuntu bionic-updates/multiverse arm64 Packages
Ign:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages
Ign:38 http://us.archive.ubuntu.com/ubuntu bionic/universe arm64 Packages
Ign:39 http://us.archive.ubuntu.com/ubuntu bionic/multiverse arm64 Packages
Err:11 http://us.archive.ubuntu.com/ubuntu bionic/main arm64 Packages
404 Not Found [IP: 91.189.91.39 80]
Ign:40 http://us.archive.ubuntu.com/ubuntu bionic-updates/main arm64 Packages
Ign:41 http://us.archive.ubuntu.com/ubuntu bionic-updates/restricted arm64 Packages
Get:42 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe arm64 Packages [1,870 kB]
Get:42 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe arm64 Packages [1,870 kB]
Get:42 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe arm64 Packages [1,870 kB]
Get:42 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe arm64 Packages [1,870 kB]
Get:42 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe arm64 Packages [1,870 kB]
Ign:42 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe arm64 Packages
Ign:43 http://us.archive.ubuntu.com/ubuntu bionic-updates/multiverse arm64 Packages
Ign:16 http://us.archive.ubuntu.com/ubuntu bionic/restricted arm64 Packages
Ign:49 http://us.archive.ubuntu.com/ubuntu bionic-backports/main arm64 Packages
Ign:50 http://us.archive.ubuntu.com/ubuntu bionic-backports/universe arm64 Packages
Err:40 http://us.archive.ubuntu.com/ubuntu bionic-updates/main arm64 Packages
404 Not Found [IP: 91.189.91.39 80]
Ign:41 http://us.archive.ubuntu.com/ubuntu bionic-updates/restricted arm64 Packages
Ign:42 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe arm64 Packages
Ign:43 http://us.archive.ubuntu.com/ubuntu bionic-updates/multiverse arm64 Packages
Ign:49 http://us.archive.ubuntu.com/ubuntu bionic-backports/main arm64 Packages
Ign:50 http://us.archive.ubuntu.com/ubuntu bionic-backports/universe arm64 Packages
Ign:49 http://us.archive.ubuntu.com/ubuntu bionic-backports/main arm64 Packages
Ign:50 http://us.archive.ubuntu.com/ubuntu bionic-backports/universe arm64 Packages
Err:49 http://us.archive.ubuntu.com/ubuntu bionic-backports/main arm64 Packages
404 Not Found [IP: 91.189.91.39 80]
Ign:50 http://us.archive.ubuntu.com/ubuntu bionic-backports/universe arm64 Packages
Fetched 405 kB in 5s (74.9 kB/s)
Reading package lists... Done
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/bionic/main/binary-arm64/Packages 404 Not Found [IP: 91.189.91.39 80]
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/bionic-updates/main/binary-arm64/Packages 404 Not Found [IP: 91.189.91.39 80]
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/bionic-backports/main/binary-arm64/Packages 404 Not Found [IP: 91.189.91.39 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
搜索 bionic/main/
grep -r -i "bionic/main" /etc/apt/
No result
搜索 bionic-updates
desktop:/etc/apt$ grep -r -i bionic-updates /etc/apt/
/etc/apt/sources.list:deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted
/etc/apt/sources.list:# deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-updates main restricted
/etc/apt/sources.list:deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates universe
/etc/apt/sources.list:# deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-updates universe
/etc/apt/sources.list:deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates multiverse
/etc/apt/sources.list:# deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-updates multiverse
搜索 bionic-backports
desktop:/etc/apt$ grep -r -i bionic-backports /etc/apt/
/etc/apt/sources.list:deb http://us.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse
/etc/apt/sources.list:# deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-backports main restricted universe multiverse