If i boot from a FreeDOS LiveCD which is mounted read only of course and try to rename a file with the following command line
ren filename.in filename.out
or
rename filename.in filename.out
Then i get a misleading error message that says:
rename: No such file or directory
The error message should be something like to be correct and more expressive and helpful:
rename: Can't rename file. Device is write protected or read only.