$ curl cheat.sh/
# 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.readthedocs.io/en/latest/mkfs.btrfs.html>.

# 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]

$
Follow @igor_chubin cheat.sh tldr