mkfs.btrfs: add page (#5441)

pages/linux/mkfs.btrfs.md

@@ -0,0 +1,17 @@
+# mkfs.btrfs
+
+> Create a btrfs filesystem.
+> Defaults to `raid1`, which specifies 2 copies of a given data block spread across 2 different devices.
+> More information: <https://btrfs.wiki.kernel.org/index.php/Manpage/mkfs.btrfs>.
+
+- Create a btrfs filesystem on a single device:
+
+`sudo mkfs.btrfs --metadata single --data single {{/dev/sda}}`
+
+- Create a btrfs filesystem on multiple devices with raid1:
+
+`sudo mkfs.btrfs --metadata raid1 --data raid1 {{/dev/sda}} {{/dev/sdb}} {{/dev/sdN}}`
+
+- Set a label for the filesystem:
+
+`sudo mkfs.btrfs --label "{{label}}" {{/dev/sda}} [{{/dev/sdN}}]`