mount notification question

mount notification question

[Daniel Lezcano]

Hi all,

is there a way to be notified when a mount occurs on the system ?

Thanks
   -- Daniel

Re: mount notification question

[Chris Friesen]

On 08/02/2010 03:12 PM, Daniel Lezcano wrote:
> 
> Hi all,
> 
> is there a way to be notified when a mount occurs on the system ?

Have you looked on google?  The link is a bit misleading but they do
give a way to do it (not using inotify).

http://stackoverflow.com/questions/1113176/how-could-i-detect-when-a-directory-is-mounted-with-inotify

Chris

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Re: mount notification question

[Daniel Lezcano]

On 08/04/2010 08:41 PM, Chris Friesen wrote:
> On 08/02/2010 03:12 PM, Daniel Lezcano wrote:
>    
>> Hi all,
>>
>> is there a way to be notified when a mount occurs on the system ?
>>      
> Have you looked on google?  The link is a bit misleading but they do
> give a way to do it (not using inotify).
>
> http://stackoverflow.com/questions/1113176/how-could-i-detect-when-a-directory-is-mounted-with-inotify
>    

Thanks a lot for the pointer. I am not sure this solution will work, 
because it is inadequate for watching a specific location in a container 
context separated by the mount and the network namespaces. We have 
multiple mount points at the same place (eg. the mount point 
inheritance, the container configuration and the init scripts may mount 
/dev or /var/run several time) and the network namespace separation will 
make impossible to watch udev event via a netlink socket. I didn't look 
at the inotify implementation but IMHO, it should be worth to add 
IN_MOUNT and IN_UNMOUNT events for inotify no ?

Thanks
   -- Daniel

Re: mount notification question

[Kay Sievers]

On Fri, Aug 6, 2010 at 03:07, Daniel Lezcano <daniel.lezcano@free.fr> wrote:
> On 08/04/2010 08:41 PM, Chris Friesen wrote:
>> On 08/02/2010 03:12 PM, Daniel Lezcano wrote:
>>> is there a way to be notified when a mount occurs on the system ?
>>
>> Have you looked on google?  The link is a bit misleading but they do
>> give a way to do it (not using inotify).
>>
>> http://stackoverflow.com/questions/1113176/how-could-i-detect-when-a-directory-is-mounted-with-inotify
>
> Thanks a lot for the pointer. I am not sure this solution will work, because
> it is inadequate for watching a specific location in a container context
> separated by the mount and the network namespaces. We have multiple mount
> points at the same place (eg. the mount point inheritance, the container
> configuration and the init scripts may mount /dev or /var/run several time)
> and the network namespace separation will make impossible to watch udev
> event via a netlink socket. I didn't look at the inotify implementation but
> IMHO, it should be worth to add IN_MOUNT and IN_UNMOUNT events for inotify
> no ?

These events wouldn't work, and they are long removed from the kernel
and don't exist.

You need to poll() /proc/mounts, and any changes in it will wake you
up with POLL_ERR. /proc/mounts should be namespace aware.

Kay

Re: mount notification question

[Daniel Lezcano]

On 08/06/2010 09:44 AM, Kay Sievers wrote:
> On Fri, Aug 6, 2010 at 03:07, Daniel Lezcano<daniel.lezcano@free.fr>  wrote:
>    
>> On 08/04/2010 08:41 PM, Chris Friesen wrote:
>>      
>>> On 08/02/2010 03:12 PM, Daniel Lezcano wrote:
>>>        
>>>> is there a way to be notified when a mount occurs on the system ?
>>>>          
>>> Have you looked on google?  The link is a bit misleading but they do
>>> give a way to do it (not using inotify).
>>>
>>> http://stackoverflow.com/questions/1113176/how-could-i-detect-when-a-directory-is-mounted-with-inotify
>>>        
>> Thanks a lot for the pointer. I am not sure this solution will work, because
>> it is inadequate for watching a specific location in a container context
>> separated by the mount and the network namespaces. We have multiple mount
>> points at the same place (eg. the mount point inheritance, the container
>> configuration and the init scripts may mount /dev or /var/run several time)
>> and the network namespace separation will make impossible to watch udev
>> event via a netlink socket. I didn't look at the inotify implementation but
>> IMHO, it should be worth to add IN_MOUNT and IN_UNMOUNT events for inotify
>> no ?
>>      
> These events wouldn't work, and they are long removed from the kernel
> and don't exist.
>
> You need to poll() /proc/mounts, and any changes in it will wake you
> up with POLL_ERR. /proc/mounts should be namespace aware.
>    

Ah, great ! I will look for this solution (I suppose I will probably 
have to diff /proc/mounts but anyway ...)

Thanks Kay and Chris for your help.

   -- Daniel