problem: Because udev only creates required devices, I cannot create a new raid, reason: device is missing Version-Release number of selected component (if applicable): mdadm-1.6.0-2 How reproducible: Always Steps to Reproduce: 1. Install RHEL4, but leave some space on the disks free 2. create partition on each disk, type fd 3. reboot to activate partitions, needed because of: WARNING: Re-reading the partition table failed with error 16: Device or resource busy. 4. try to create raid: # mdadm --create /dev/md2 --level 1 --raid-devices 2 /dev/sd[ab]5 Actual Results: mdadm: error opening /dev/md2: No such file or directory Expected Results: Working Additional info: # ll /dev/md* brw-rw---- 1 root disk 9, 0 Mar 10 17:14 /dev/md0 brw-rw---- 1 root disk 9, 1 Mar 10 17:14 /dev/md1 Workaround: # mknod /dev/md2 b 9 2 && mdadm --create /dev/md2 --level 1 --raid-devices 2 /dev/sd[ab]5 mdadm: array /dev/md2 started. Perhaps mdadm should get smarter and create missing devices (or request creation using udev). BTW: one can extend mknod also to understand "mdX" automagically like already on "hdX".
This isn't a bug. The mdadm program, as per the upstream developer's wishes, does not currenly automatically create device nodes. In order to have mdadm create the device node as part of the array creation process, the option --auto=yes may be passed on the create command line and it will do as you are expecting. Further details of the --auto option can be found in the man page for mdadm.