dephtu@dephtop:~$ sudo mdadm --create /dev/md0 --chunk=64 --level=raid1 --raid-devices=2 /dev/sda1 /dev/sdb1
mdadm: error opening /dev/md0: No such file or directory
dephtu@dephtop:~$ sudo mkdir /dev/md0
dephtu@dephtop:~$ sudo mdadm --create /dev/md0 --chunk=64 --level=raid1 --raid-devices=2 /dev/sda1 /dev/sdb1
mdadm: error opening /dev/md0: Is a directory
dephtu@dephtop:~$ sudo rmdir /dev/md0
dephtu@dephtop:~$ sudo gedit /dev/md0
dephtu@dephtop:~$ sudo mdadm --create /dev/md0 --chunk=64 --level=raid1 --raid-devices=2 /dev/sda1 /dev/sdb1
mdadm: /dev/md0 does not appear to be an md device