Devuan（无systemd的Debian Bullseye）执行apt upgrade遇I/O错误的排查修复求助

我用的是不带systemd的Debian Bullseye（也就是Devuan），今天打算升级系统里的软件包，于是输入了命令：

sudo apt upgrade

结果操作失败了，弹出了一堆错误提示——我把瑞典语的系统提示用谷歌翻译转成了英文，内容如下：

dpkg: error processing archive /var/cache/apt/archives/linux-image-5.10.0-25-amd64_5.10.191-1_amd64.deb (--unpack):
could not read status of "./boot/System.map-5.10.0-25-amd64" (which was just about to install): Input/output error
dpkg-deb: error: subprocess paste was killed by signal (The pipe was broken)
W: Last kernel image has been removed, so removing the default symlinks
An error occurred while processing:
/var/cache/apt/archives/linux-image-5.10.0-25-amd64_5.10.191-1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

我尝试用apt --fix-broken install来修复损坏的包依赖，但还是没用。谷歌搜了好一阵，也没找到和我这个情况完全匹配的解决方案，想请教下这个错误到底是什么意思，我该怎么调试和修复它？

编辑1：附上我的sources.list内容

$ cat /etc/apt/sources.list
# deb cdrom:[Devuan GNU/Linux 4.0 chimaera amd64 - desktop 20211012]/ chimaera contrib main non-free

deb http://deb.devuan.org/merged chimaera main
deb-src http://deb.devuan.org/merged chimaera main

deb http://pkgmaster.devuan.org/merged chimaera-security main
deb-src http://pkgmaster.devuan.org/merged chimaera-security main

# chimaera-updates, to get updates before a point release is made;
# see https://www.debian.org/doc/manuals/debian-reference/ch02.en.html#_updates_and_backports
deb http://deb.devuan.org/merged chimaera-updates main
deb-src http://deb.devuan.org/merged chimaera-updates main

编辑2：问题已解决！
折腾了半天终于找到原因了——我的/boot目录是挂载在一个可插拔的USB驱动器上的，平时开机之后我就把这个U盘拔掉了。刚才我把U盘重新插回电脑，再执行升级操作，居然一切都正常完成了！

备注：内容来源于stack exchange，提问作者Mikke Mus