udev-104 change in example rules

udev-104 change in example rules

[Jürg Billeter]

Hi Kay,

you've changed the example persistent storage rules to ignore md*
devices. Why have you changed that? I'm happily using /dev/disk/by-label
(and by-uuid) symlinks with a RAID device which wouldn't work anymore
with the new rules.

Regards,

Jürg
-- 
Jürg Billeter <j@bitron.ch>


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Re: udev-104 change in example rules

[Kay Sievers]

On Sat, 2007-01-13 at 10:53 +0100, Jürg Billeter wrote:
> you've changed the example persistent storage rules to ignore md*
> devices. Why have you changed that? I'm happily using /dev/disk/by-label
> (and by-uuid) symlinks with a RAID device which wouldn't work anymore
> with the new rules.

It is unreliable in its current form, so we should not enable it this
way by default. We had similar issues with device-mapper devices, where
udev opens the devices on uevents, which come in the way of the raid
admin-tools.

Md had broken lifetime-rules (should be fixed now) where /sys/block/md*
devices could be changed to have complete different content, without
updating any of the persistent links. /dev/md0 was created on open(),
even when there was no content behind, and no setup or change of the
array lead to updated links. So you are just lucky, that it worked for
you. :)

MD will have its own rules file, just like dm has. With kernel 2.6.19,
something like this could work, but I didn't try it until now:
  # md links hook into "change" events, when the array becomes available

  KERNEL="md[0-9]*", ACTION="add|change", GOTO="md_do"
  GOTO="md_end"

  LABEL="md_do"
  ATTR{md/array_state}="|clear|inactive", GOTO="md_end"

  IMPORT{program}="vol_id --export $tempnode"
  ENV{ID_FS_USAGE}="filesystem|other|crypto", ENV{ID_FS_UUID}="?*", SYMLINK+="disk/by-uuid/$env{ID_FS_UUID}"
  ENV{ID_FS_USAGE}="filesystem|other", ENV{ID_FS_LABEL_SAFE}="?*", SYMLINK+="disk/by-label/$env{ID_FS_LABEL_SAFE}"

  LABEL="md_end"


Therea are also upcoming changes to the mdadm tool, which allow auto-assembly
of md-devices, completely driven by kernel events and no by an init-script. This
will also go into the md rule-file.

Kay


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