[Bug 1550823] Re: checkarray doesn't work with sh = dash

[swmike]

Hi,

I just ran into this. I am active on both the linux-raid mailing list,
and on the #linux-raid IRC channel. We frequently get people in both
places who have problems with their arrays, some of them is because of
lack of frequent "scrubbing" to find read errors on the drives.

This issue needs to be fixed before it turns into a huge disaster. The
current default behaviour of checkarray cron is that it's run first
sunday every month. This is a sensible default, but it's now broken in
Ubuntu.

Please fix this, before people start to lose data because checkarray
isn't currently working.

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https://bugs.launchpad.net/bugs/1550823

Title:
  checkarray doesn't work with sh = dash

Status in mdadm package in Ubuntu:
  Triaged
Status in mdadm source package in Xenial:
  Triaged
Status in mdadm package in Debian:
  New

Bug description:
  As per https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=787950,
  /usr/share/mdadm/checkarray fails when it tries to read
  /sys/block/mdX/md/sync_action, if running under dash (or apparently
  most shells other than bash), with a 4.x kernel.

  Present in Ubuntu 15.10, where a default install does use /bin/sh ->
  dash, and runs Linux 4.2.

  A simple workaround is to make it a #!/bin/bash script.  Another
  alternative would be to read sync_action with cat, instead of the read
  built-in, since (as a reply on the Debian bug report says), the
  problem is char-at-a-time reading of the file in /sys.

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