[feature request] extract a single file from EROFS filesystem

[Mingye Wang]

Hi all,

>Gao Xiang Thu, 09 Jan 2025 01:36:16 -0800
>On 2025/1/9 02:14, Daniel Erez wrote:
>>Would it be applicable to introduce an option for extracting a specific file
>>from the image?
>>I.e. something similar to the '-extract-file' option available in unsquashfs tool [2].
>I will add this later.

I am seeing a need for a similar feature in making dracut's lsinitrd
work... a little better. I should add two cents of my own.

* In "unsquashfs" there's not only '-extract-file' for passing in a
list of files, but also a possibility for a list of paths to be
specified directly as arguments. This would appear outlandish on an
fsck utility.
* When extracting single files it might be desirable to *not* verify
and pretend-extract the other files.

Because of these two reasons, I think it might be best to make an
"unerofs" for extraction purposes instead of adding more things to the
"fsck" tool. An initial version can just be a separate "main" fuction
in fsck.c that gets used when an argv[0] equal to "unerofs" or ending
with "/unerofs" is found.

Sincerely,
Mingye Wang (Artoria2e5)