China DOS Union

I downloaded the DOS 6.22 boot disk.
I used UNDISK to extract the DOS boot disk to drive A:, but why does it report an error? The exact command is:
undisk c:\msdos6.22\msdos6.22.img a:
Is there something wrong with this command?

msdos6.22.img

Yes, there is! This does not conform to DOS's 8.3 filename rule! Note that your filename has two dots, and this is illegal under DOS.

Also, next time when you make a post, remember to use a better title, okay? Don't leave it blank every time...

UNDISK can't directly extract it to a floppy like this to make a boot disk; DI, HD-COPY, etc. can.

UNDISK does not support long filenames, while DOSIMG and the like do.

I suggest downloading an MS-DOS 7.10 boot floppy instead; its compatibility and practicality are much better.

Can a DOS 7.10 boot disk boot DOS 6.22?

Of course a DOS 7.10 boot disk boots DOS 7.10, not the old 6.22 version.