Question on mdev's custom command invocation

[Olivier Brunel]

On Wed, 16 Nov 2016 16:27:12 +0100
Didier Kryn <kryn at in2p3.fr> wrote:

>      Hello.
> 
>      I'm willing to create/delete symlinks in /dev/disk/by-uuid and 
> /dev/disk/by-label . For this, I've written a script and added the 
> following lines to /etc/mdev.conf:
> sd[a-z][0-9]*   root:disk 660 */sbin/mdev-disk
> hd[a-z][0-9]*   root:disk 660 */sbin/mdev-disk
> 
>      Note that I use /dev/mdev.seq to serialize events.
> 
>      Is there a means for my script mdev-disk to determine if the
> device is being inserted or extracted? For example it would be easy
> if mdev provided the uevent's action (add, remove)

I'm assuming you already use environment variables in your script,
e.g. $MDEV, $SEQNUM, etc Maybe you missed $ACTION, sounds like what
you're looking for.

HTH,


>      My current trick is to create links when they don't exist and 
> delete them when they exist, but it's far from rock-solid.
> 
>      Possible alternatives I see are:
>          - use different commands for insertion and extraction - not 
> sure mdev.conf allows to have two lines per device pattern
>          - monitor /dev with inotify instead of using a command
> launched by mdev, but this process would be constantly there sleeping.
> 
>      Thanks for your help.
>                                                  Didier
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