FC3 mdadm issue

[Robin Bowes]

Aaron M. Hirsch wrote:
> I created md0-3 during boot and now want to create another raid device 
> which would be md4.  I've gone through the man page and searched online 
> but am coming up blanks for an answer.  I am using FC3 x86_64...
> 
> To create the new raid device I ran:  mdadm --create /dev/md4 --level=0 
> --raid-disks=2 /dev/hda6 /dev/hdc6 which errors out stating: mdadm: 
> error opening /dev/md4: No such file or directory.  Of course it's not 
> there yet, I'm just now trying to create it.

I ran into this yesterday.

You have two options:

1. From Luca Berra: "you could use the --auto= option of mdadm to have 
it create the device for you, the only issue with that is that mdadm 
will use the first free minor numbr it finds instead of using the minor 
implied by the device name. (i was planning on changing that behaviour 
sooner or later)."

2. Use mknod to create the device before creating the array. Here's what 
I did to create /dev/md2:

# [root at dude dev]# mknod --help
Usage: mknod [OPTION]... NAME TYPE [MAJOR MINOR]
Create the special file NAME of the given TYPE.

   -Z, --context=CONTEXT   set security context (quoted string)
Mandatory arguments to long options are mandatory for short options too.
   -m, --mode=MODE   set permission mode (as in chmod), not a=rw - umask
       --help     display this help and exit
       --version  output version information and exit

Both MAJOR and MINOR must be specified when TYPE is b, c, or u, and they
must be omitted when TYPE is p.  If MAJOR or MINOR begins with 0x or 0X,
it is interpreted as hexadecimal; otherwise, if it begins with 0, as octal;
otherwise, as decimal.  TYPE may be:

   b      create a block (buffered) special file
   c, u   create a character (unbuffered) special file
   p      create a FIFO

Report bugs to <bug-coreutils at gnu.org>.

[root at dude dev]# file /dev/md1
/dev/md1: block special (9/1)
[root at dude dev]# file /dev/md0
/dev/md0: block special (9/0)
[root at dude dev]# file /dev/md5
/dev/md5: block special (9/5)
[root at dude dev]# mknod /dev/md2 b 9 2
[root at dude dev]# ls /dev/md2
/dev/md2

Done!

(If you don't have the array set to auto-start, you'll have to add the 
"mknod" command to your system startup scripts before trying to start 
the array directly)

R.