Hi,

Jeffrey J. Kosowsky wrote on 2011-08-04 01:37:23 -0400 [Re: [BackupPC-users] 
How do I configure DumpPreUserCmd to have multiple?commands]:
> Rory Toma wrote at about 18:15:32 -0700 on Wednesday, August 3, 2011:
>  > [...]
>  > In my case, I want to do something like:
>  > 
>  > rsh -n <machine> <command>; rsh -n <machine> command ; ls <sharename>; 
>  > ls <sharename2>
> 
> As the config.pl inline documentation *clearly* states:
> # Note: all Cmds are executed directly without a shell, so the prog name
> # needs to be a full path and you can't include shell syntax like
> # redirection and pipes; put that in a script if you need it.
> 
> Chaining together multiple commands separated by a ";" is a *shell*
> feature.
> 
> So either package it all into an explicit shell command directly, e.g.,
>    bash -c "rsh -n <machine> <command>; rsh -n <machine> command ; \
>    ls <sharename>; ls <sharename2>"

I'm not sure that works. As you know, *quoting* is also a shell feature. Now,
bash just *might* reparse its command line arguments, remove quotes, and
recombine arguments, but I don't feel that is very likely, because whitespace
between arguments will have been lost and can only be replaced by single blanks
(which may or may not be what was previously there). Quoting is simply
something that needs to be done before invoking bash to get it right. However,
there might be a special case for the argument to -c starting with a quote.

So, if bash *doesn't* recombine arguments, according to the man page, only the
first one will be interpreted as a command ('"rsh'). This would mean that
there would in fact be no way to make this work without changing the BackupPC
code.

You *could*, however, use Perl code to achieve the same thing.

        $Conf{DumpPreUserCmd} = '&sub{ system ("...");}';

where "..." is your 'rsh; rsh; ls; ls' sequence (system() uses a shell if it
finds shell metacharacters - such as a semicolon - in the command).

Disclaimer: both that the 'bash -c' version doesn't work and that the Perl
version does are untested.

> Or package it all together into a shell shell secret

That is probably meant to read "shell script" ;-). That is without doubt the
most simple solution (and the one recommended in the config.pl comment).

Note also that "rsh" (do you really mean "rsh" and not "ssh"!?) *does*
execute a shell (and accept the command to be run in an arbitrary amount of
command line arguments), so you could also use something like

        rsh -n <machine> <command1>; <command2>

to run both <command1> and <command2> on <machine> (this also means your
example above should, in fact, have worked, except for running the second
'rsh' command and the 'ls'es on <machine>, which may or may not be meaningful).
I don't quite understand the point in the 'ls' commands, which only seem to
list the directory contents to the log file (which might be useful for
debugging, but shouldn't make a difference for backup operation, unless the
second 'ls' returns an error exit status ...).

Hope that helps.

Regards,
Holger

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