December 2002
Intermediate to advanced
260 pages
9h 18m
English
Content preview from Managing RAID on LinuxBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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md Block Special Files
The block special files /dev/md[0-255]
provide access to software RAID devices. The md
driver uses a major number of 9. On most systems, all of these files are
created when the system is installed. If an md
block special file is missing, you will get an error like:
error opening /dev/md31: No such file or directory
from mdadm or raidtools. You
can create the file yourself using the mknod
command. The following example creates the block special file used to
access /dev/md31 with a umask of
0660:
#mknod -m 0660 /dev/md31 b 9 31#chown root.disk /dev/md31
I specified b for block special file,
9 for the md major number, and
31 for the minor number. In general, the minor number
and the number for the device name are the same. I also made certain
that user and group ownership was set to root and
disk, respectively. Repeat these commands for any
device file you need to create manually.
Some distributions also come with the MAKEDEV program, usually found in /dev, although sometimes it is found as a symbolic link to /sbin/MAKEDEV. MAKEDEV can be used to create all the special files for any character or block device. It’s more user-friendly than mknod, but MAKEDEV might not be available on all systems.
The following example uses MAKEDEV to create all the block special md files:
# /dev/MAKEDEV -v md
create md0 b 9 0 root:disk 660
create md1 b 9 1 root:disk 660
[...]
create md30 b 9 30 root:disk 660
create md31 b 9 31 root:disk 660MAKEDEV will overwrite old device nodes. ...
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