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Re: Problem with 'df' on RedHat Linux with multiple "namespaces"
From: |
Pádraig Brady |
Subject: |
Re: Problem with 'df' on RedHat Linux with multiple "namespaces" |
Date: |
Fri, 01 Jan 2010 01:10:47 +0000 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.5) Gecko/20091204 Thunderbird/3.0 |
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.