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Some really weird Voodoo magic is going on with mdadm in my script:

Creating RAID with: mdadm --create --run --level=1 --metadata=1.2 --raid-devices=2 /dev/md/4  /dev/nvme1n1p4  /dev/nvme0n1p4
mdadm: /dev/nvme1n1p4 appears to contain an ext2fs file system
       size=495889752K  mtime=Thu Jan  1 01:00:00 1970
mdadm: /dev/nvme0n1p4 appears to be part of a raid array:
       level=raid1 devices=2 ctime=Sun Jul 21 16:58:43 2024
mdadm: array /dev/md/4 started.
------------
Creating RAID with: mdadm --create --run --level=1 --metadata=1.2 --raid-devices=2 /dev/md/4  /dev/nvme1n1p4  /dev/nvme0n1p4  > /dev/null
mdadm: You have listed more devices (4) than are in the array(2)!
------------
Creating RAID with: mdadm --create --run --level=1 --metadata=1.2 --raid-devices=2 /dev/md/4  /dev/nvme1n1p4  /dev/nvme0n1p4  > /dev/null 2>&1
mdadm: You have listed more devices (5) than are in the array(2)!

Just look at the 2 lower examples where I try to mute the output of mdadm to only produce the output I want. It produces a completely unrelated error message.

Here is the bash section that causes the issue:

else \
  echo "Continuing with Software RAID1"; \
  for partition in {1..4}; do \
    raidCommand="mdadm --create --run --level=1 --metadata=1.2 --raid-devices=${targetDriveCount} /dev/md/${partition} " && \
    for drive in $targetDrives; do \
      if [[ "$drive" == *nvme* ]]; then \
        raidCommand="${raidCommand} ${drive}p${partition} "; \
      else \
        raidCommand="${raidCommand} ${drive}${partition} "; \
      fi; \
    done; \
    raidCommand="${raidCommand} > /dev/null 2>&1" && \
    echo "Creating RAID with: ${raidCommand}" && \
    $raidCommand; \
  done; \
fi && \

The script works, but this output is not clean at all. How can I prevent this from happening? And yeah I know, the script does not look great, but it should do for now. And yes, it actually is a single liner intentionally. But that does not explain the error in any way I can understand at all. What is going on?

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  • 4
    AFAIK the unquoted expansion $raidCommand performs word splitting and globbing, but doesn't magically perform redirections - so > , /dev/null, and 2>&1 are all passed to mdadm as additional arguments Commented Jul 21, 2024 at 15:29
  • 1
    ... see for example Passing a command with arguments and redirection to a function or How to use output redirection dynamically? Commented Jul 21, 2024 at 15:35
  • 1
    What's with all the trailing \ characters? Commented Jul 21, 2024 at 18:25
  • 2
    "It actually mutes all output of mdadm - except the error you see in this example" – I think the tool reports the fatal error and does nothing more; so "all the output except" is not muted, it's not there in the first place. Commented Jul 21, 2024 at 20:37
  • 1
    Side note: there are better (or at least less cumbersome) ways to be able to "copy&paste to bash directly": bracketed paste, grouping commands ({ … }), edit-and-execute-command (Ctrl+x, Ctrl+e) or even putting everything in a shell function and calling it. Commented Jul 21, 2024 at 20:50

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