btrbk: add page (#7991)

pages/linux/btrbk.md

@@ -0,0 +1,24 @@
+# btrbk
+
+> A tool for creating snapshots and remote backups of btrfs subvolumes.
+> More information: <https://digint.ch/btrbk/doc/readme.html>.
+
+- Print statistics about configured subvolumes and snapshots:
+
+`sudo btrbk stats`
+
+- List configured subvolumes and snapshots:
+
+`sudo btrbk list`
+
+- Print what would happen in a run without making the displayed changes:
+
+`sudo btrbk --verbose dryrun`
+
+- Run backup routines verbosely, show progress bar:
+
+`sudo btrbk --progress --verbose run`
+
+- Only create snapshots for configured subvolumes:
+
+`sudo btrbk snapshot`