add fsused to block_devices output

src/system.js

@@ -324,7 +324,7 @@ async function getLogs(unit, options) {
 
 // this gets block devices as opposed to mounted filesystems. this is used for configuring backups and volumes in the frontend
 async function getBlockDevices() {
-    const output = await shell.spawn('lsblk', ['--paths', '--json', '--list', '--fs', '--output', '+rota'], { encoding: 'utf8' });
+    const output = await shell.spawn('lsblk', ['--paths', '--bytes', '--json', '--list', '--fs', '--output', '+rota,fsused,fsavail'], { encoding: 'utf8' });
     const info = safe.JSON.parse(output);
     if (!info) throw new BoxError(BoxError.INTERNAL_ERROR, `failed to parse lsblk: ${safe.error.message}`);
 
@@ -340,6 +340,7 @@ async function getBlockDevices() {
         result.push({
             path: device.name,
             size: device.fsavail || 0,
+            used: device.fsused || 0,
             type: device.fstype, // when null, it is not formatted
             uuid: device.uuid,
             rota: device.rota, // false (ssd) true (hdd) . unforuntately, this is not set correctly when virtualized (like in DO)