Add parser for mdadm

Linux software RAID is usually implemented with the md kernel module and managed with the mdadm userspace tool. Unfortunately mdadm doesn’t output it’s data in a format convenient for further automated processing like json.

For example when using mdadm --query --detail /dev/md0 the output looks like this:

/dev/md0:
           Version : 1.1
     Creation Time : Tue Apr 13 23:22:16 2010
        Raid Level : raid1
        Array Size : 5860520828 (5.46 TiB 6.00 TB)
     Used Dev Size : 5860520828 (5.46 TiB 6.00 TB)
      Raid Devices : 2
     Total Devices : 2
       Persistence : Superblock is persistent

     Intent Bitmap : Internal

       Update Time : Tue Jul 26 20:16:31 2022
             State : clean 
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : bitmap

              Name : virttest:0
              UUID : 85c5b164:d58a5ada:14f5fe07:d642e843
            Events : 2193679

    Number   Major   Minor   RaidDevice State
       3       8       17        0      active sync   /dev/sdb1
       2       8       33        1      active sync   /dev/sdc1

mdadm also has the “examine” command which gives information about a md raid member device:

# mdadm --examine -E /dev/sdb1
/dev/sdb1:
          Magic : a92b4efc
        Version : 1.1
    Feature Map : 0x1
     Array UUID : 85c5b164:d58a5ada:14f5fe07:d642e843
           Name : virttest:0
  Creation Time : Tue Apr 13 23:22:16 2010
     Raid Level : raid1
   Raid Devices : 2

 Avail Dev Size : 11721041656 sectors (5.46 TiB 6.00 TB)
     Array Size : 5860520828 KiB (5.46 TiB 6.00 TB)
    Data Offset : 264 sectors
   Super Offset : 0 sectors
   Unused Space : before=80 sectors, after=0 sectors
          State : clean
    Device UUID : 813162e5:2e865efe:02ba5570:7003165c

Internal Bitmap : 8 sectors from superblock
    Update Time : Tue Jul 26 20:16:31 2022
  Bad Block Log : 512 entries available at offset 72 sectors
       Checksum : f141a577 - correct
         Events : 2193679


   Device Role : Active device 0
   Array State : AA ('A' == active, '.' == missing, 'R' == replacing)

Having a parser for this in jc would be really helpful when dealing with md raid in scripts.

[g-v-egidy]

I tested your latest version. It is looking very good to me now, it now gets all values I care for and some more.

Thank you for implementing this parser.

[g-v-egidy]

I don’t have a raid setup so it’s a little difficult for me to check out all of the output possibilities.

Just an idea if you want to try it for yourself: use a virtual machine and add a second, empty virtual disk to it. Then you can use that to play around with the different setups. This is what I have been doing to create the output examples.

I’ve been using https://www.system-rescue.org/ as linux in the virtual machine, because you don’t have to install anything, just add the iso image and it boots.