如何仅使用Java挂载设备？

Question

Okay, I realize this might not be possible ...

I have a device that runs linux, and it will likely not have a user interface that is visible. It will have a USB port that is open ... I want to be able to write java to allow the overall system to detect when a device is plugged into the USB port and then mount the device.

I know how to do this from a command line, but it requires "sudo" to fork a new process with elevated privilege to perform the task. I don't know how to write a java program that can get around (yes, I want to get around) the security protection of mount.

runtime.exec() doesn't really do what I am hoping to accomplish. Is this a "can't be done in Java" problem?

I'm hoping to do this without resorting to external executable code.

Answer 1

You can't get around the security protection of mount. The protection is not in mount. The protection is in the kernel.

If by chance you find a way and publish it, it will get removed.

If you have control of the OS you are running on, you can add the option user to the mountpoint in /etc/fstab. After doing so, "mount /path" and "umount /path" work from runtime.exec() without elevation. mount and umount are setuid-root to allow this to work.

Answer 2

File mounts are controlled by the host operating system. So controlling mounts is done through system calls. You seem to be using a Unix operating system, so that means the system call interface is C. So you could use JNI to call a small C function that makes the system call needed.

But all such matters are system dependent, and privileged operations. So that approach creates portability and security problems. So you might do better to reconsider why your program itself must do this, rather than letting a control component (such as systemd ) do it for you.