Re: Problem with 'df' on RedHat Linux with multiple "namespaces"

[Pádraig Brady]

On 31/12/09 18:00, Lenga, Yair wrote:
> Hi
>
> I have an application that is using the Linux "unshare" system calls
> (on RedHat 5, or "clone" with CLONE_NEWNS), to allocate different volumes
> for different processes on the same mount point. This setup is used to
> allow multiple processes to run against different data sets, without
> having to change the code.
> The 'df' command will report ALL the mount points of the system.
> I believe the order is based on the order of the mounts (first mounts
> listed first). For example, the system has '/home/ mounted from a file
> server, then few processes establish a local '/home/data' tree. For example:
> $ df
> Filesystem           1K-blocks      Used Available Use% Mounted on
> /dev/sda2              8064304   1835928   5818720  24% /
> /dev/sda1               101086     12178     83689  13% /boot
> none                   4155280         0   4155280   0% /dev/shm
> /dev/sda5             57874464  13076584  41857988  24% /home2
> appnfs1:/home/dev    258144000  98499552 159644448  39% /home
> /dist/2a             258144000  98499552 159644448  39% /home/data
> /dist/5a             258144000  98499552 159644448  39% /home/data
> /dist/7a             258144000  98499552 159644448  39% /home/data
>
> The problem occur when typing 'df /home/data'. The output is:
>
> $ df /home/data
> Filesystem           1K-blocks      Used Available Use% Mounted on
> /dist/2a             258144000  98499552 159644448  39% /home/data
>
> This is very misleading (and probably wrong), as the /dist/data
> for the current process is on the "appnfs1" volume. It looks as
> the translation code that move from a path (e.g. /home/data),
> find the first match, regardless of the namespace associated for
> the current process. This logic cause few scripts to fail (e.g.,
> we have a script that checked for free space, before attempting
> to upload large number of files).
> Please let me know if you need additional information.

I'm not sure it's related but could you give the output from
df -P as the -P option should always be used from scripts.

cheers,
Pádraig.