> You can also mount a read-only ramdisk in between the root filesystem
> (if it needs to be mounted read-write) and the usb. Assuming the
> directory is /mnt/log. Something similar to those lines in /etc/fstab
> may (untested) work.
>
> tmpfs /mnt/log tmpfs defaults,ro 0 0
> /dev/usb-block /mnt/log ext4 defaults 0 0
In the same vein, there's also
mount -o bind,ro /emptydir /var/log
=== Stefan