Re: `losetup --remove` is confusing, and misuse silently fails

[Nuno Silva <nunojsilva@ist.utl.pt>]

On 2025-10-10, Benno Schulenberg wrote:

> After setting up a loop device with:
>
>   # ./losetup loop4 some.img
>
> I wanted to see what happens when trying to "remove" it
> (since the man page says it is "not recommended"):
>
>   # ./losetup -R loop4
>
> There is no feedback, but it failed:
>
>   # echo $?
>   1
>
> When a command fails, shouldn't it print an error message?

For all commands after this one in your message, where there was no
output, what was the exit status?

[...]
> Trying a different order of the options:
>
>   # ./losetup -d -R loop4
>   losetup: /dev/-R: detach failed: No such file or directory
>
> Huh?  Why does it try to interpret an option as a loop device name?

The online manual here says that -d takes one argument, so my
understanding is that that is expected? (Just as for -R, apparently:)

>   # ./losetup -d loop4 -R
>   /home/ben/Sources/util-linux/.libs/losetup: option requires an argument -- 'R'
>   Try 'losetup --help' for more information.
>
>   # ./losetup -d loop4 -R loop4
>
> Oh.  Surprisingly, this last invocation worked.

[...]

-- 
Nuno Silva