如何使 du 命令抛出输入/输出错误

Question

How to make du command throw input/output error . For some reason, I want to reproduce this use case and want to verify my fix before changes pushed to production. I am not able to understand how to reproduce this use case. I tried so many thing, but no luck. Any other command also fine which throws input/output error for file system.

Eg

du -sh /data/
du: cannot access '/data/': Input/output error

Answer 1

The error message appears to be EIO . The man page says

EIO Input/output error (POSIX.1-2001).

In-turn, POSIX says :

Input/output error. Some physical input or output error has occurred. This error may be reported on a subsequent operation on the same file descriptor. Any other error-causing operation on the same file descriptor may cause the [EIO] error indication to be lost.

So, where does that leave you? Well, you need to somehow simulate du receiving EIO from a syscall. You should be able to use strace to make an arbitrary syscall return EIO , but which one?

Start by running du under strace to see which syscalls might return EIO. fstat(2) does not return EIO on Linux, so it must be another syscall.