bcachefs: update header; bcachefs-device: add page (#13770)

pages/linux/bcachefs-device.md

@@ -0,0 +1,16 @@
+# bcachefs device
+
+> Manage devices within a running `bcachefs` filesystem.
+> More information: <https://bcachefs-docs.readthedocs.io/en/latest/mgmt-devicemanagement.html>.
+
+- Format and add a new device to an existing filesystem.:
+
+`sudo bcachefs device add --label={{group}}.{{name}} {{path/to/mountpoint}} {{path/to/device}}`
+
+- Migrate data off a device to prepare for removal:
+
+`bcachefs device evacuate {{path/to/device}}`
+
+- Permanently remove a device from a filesystem:
+
+`bcachefs device remove {{path/to/device}}`

pages/linux/bcachefs.md

@@ -1,7 +1,8 @@
 # bcachefs
 
 > Manage `bcachefs` filesystems/devices.
-> More information: <https://bcachefs.org/bcachefs-principles-of-operation.pdf>.
+> Some subcommands such as `device` have their own usage documentation.
+> More information: <https://bcachefs-docs.readthedocs.io/en/latest/index.html>.
 
 - Format a partition with `bcachefs`: