> Hi I am looking to make use of the lhsmtool_cmd, and im having trouble
> understanding the use of the FD(File Descripter) varable requierd by
> the tool. Is there anyone that can assist with my understanding? I'v
> had a look unsuccessfully and at some examples, as well as run the
> example with DD.
>
> Kind Regards
>
> - Alasdair King
Hi,
The FD is a file descriptor (integer) where the subprocess (the command
which is spawned by the copytool) can read or write - depending whether
it is archiving or restoring - data in Lustre.
It is opened by the parent process, which receives and processes
requests from the coordinator and passed to the subcommand so that it
does not have to re-open the file. Internally, it is provided by
llapi_hsm_action_get_fd().
Because we want to be able to invoke arbitrary commands, we cannot use
the standard sendmsg/recvmsg to pass FDs between processes and instead
rely on /proc/self/{fd} to work with commands that expect paths, like
dd.
Hope this makes sense
Regards
--
Henri
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