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. Thanks Yair Lenga
