[ mike in ~/etc/new-old-computer ]$ mount -o loop linux.iso iso-tmp/
mount: only root can do that
[ mike in ~/etc/new-old-computer ]$ sudo mount -o loop linux.iso iso-tmp/
[ mike in ~/etc/new-old-computer ]$ touch foo
[ mike in ~/etc/new-old-computer ]$ cp foo iso-tmp/
cp: cannot create regular file `iso-tmp/foo': Read-only file system
[ mike in ~/etc/new-old-computer ]$ sudo mount -o remount,rw linux.iso iso-tmp/
[ mike in ~/etc/new-old-computer ]$ cp foo iso-tmp/
cp: cannot create regular file `iso-tmp/foo': Read-only file system