• 具体错误

$ sudo debtap -u
==> Synchronizing pkgfile database...
:: Updating 2 repos...core is up to dateextra is up to date
==> Synchronizing debtap database...% Total    % Received % Xferd  Average Speed   Time    Time     Time  CurrentDload  Upload   Total   Spent    Left  Speed0   260    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (22) The requested URL returned error: 404gzip: /var/cache/debtap/debian-main-packages-files.gz: unexpected end of file% Total    % Received % Xferd  Average Speed   Time    Time     Time  CurrentDload  Upload   Total   Spent    Left  Speed0   260    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (22) The requested URL returned error: 404gzip: /var/cache/debtap/debian-non-free-packages-files.gz: unexpected end of file% Total    % Received % Xferd  Average Speed   Time    Time     Time  CurrentDload  Upload   Total   Spent    Left  Speed0   260    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0
curl: (22) The requested URL returned error: 404gzip: /var/cache/debtap/debian-contrib-packages-files.gz: unexpected end of file% Total    % Received % Xferd  Average Speed   Time    Time     Time  CurrentDload  Upload   Total   Spent    Left  Speed0   278    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (22) The requested URL returned error: 404gzip: /var/cache/debtap/ubuntu-packages-files.gz: unexpected end of file
Synchronization failed. Exiting...

• 解决步骤1

编辑/usr/bin/debtap：

ftp.debian.org/archive.ubuntu.com
改为
mirrors.ustc.edu.cn

• 解决步骤2

上面步骤解决了网站可能联接不上的问题。我在riscv64 Arch Linux上，更新还是报错。反复安装、更新都不对。一怒之下，分析了一下debtap，怀疑有问题。先在浏览器上输入了http://mirrors.ustc.edu.cn相关目录，确实有很多东西。于是怀疑是$_arch这个变量不对。于是进行了手工替换：

http://mirrors.ustc.edu.cn/debian/dists/sid/main/Contents-$_arch.gz
改成
http://mirrors.ustc.edu.cn/debian/dists/sid/main/Contents-riscv64.gz