Re: [BackupPC-users] Solaris ping command and Config.pl association

[<cba...@us...>]

> After a couple weeks of shutting down my workstation over the weekend, I
> noticed that the server didn't remove it from the "blackout" list.
> After looking into it (I won't tell you how much time it
> took...*grrrr*), I found that the ping command wasn't returning a
> positive error status, when using the "-s" parameter.  Thus:
>  
>     /usr/sbin/ping -s <non-responding IP> 56 1
>     ...
>     echo $?
>     0                 <-- should have been positive
>  
> I verified this on Solaris 2.6 and 2.7.  The ping command works
> correctly on Solaris 2.8 (and probably 2.9).  Couldn't find anything on
> sunsolve or elsewhere.  The result was that the ping test succeeded.
> Then the xfer routines kicked in which failed with "Got fatal error
> during xfer (Connection to <host> failed)" messages.  The quick fix was
> to just use "ping $host 1" as the test and while it doesn't allow for
> RTT, the code in Lib.pm (CheckHostAlive) will return zero if it can't
> match any "time" string.

Good detective work.  I should add this to the FAQ, although I haven't
started it yet.

> Craig, ever think about using the Perl "ping" library?  Just wondering,
> mind you.

Real pings (ICMP) needs to run as root.  Typically /usr/sbin/ping
is setuid root.  So that's not an option since we don't want to
setuid root.  Net::Ping also supports a UDP or TCP ping (not sure
which ports it uses), which might not work on all hosts.  I also
wanted to minimize the number of additional perl modules that need
to be installed, but the price to pay is users having to deal with
numerous versions of ping.

In BackupPC 2.0.0 an undocumented feature is that all commands (eg: the
ping command) can be replaced in the config file by snippets of perl code.
So you could use Net::Ping if you want just by using the correct settings
in config.pl.

> I also noticed an oddity, perhaps by design (Craig?).  Even if you
> haven't defined a host in the "conf/hosts" file, you can still use
> BackupPC_dump to do a backup.  Several conditions must be met, mind you
> (share, share password, etc.).  The host directory must exist, also.
> This could be interesting for quick tests but the code seems to only use
> the "server" config.pl even if you have created one in the host's
> directory.  I assume this is due to the fact that the daemon doesn't
> know about the host and any attempt to access {Conf} will always point
> to the server config.  Perhaps a check for config validity before
> allowing a backup?

You're right: it never checks that the host exists.  This wasn't deliberate;
I wasn't thinking about the case of BackupPC_dump being used manually.
It probably even creates a host directory too, which is undesirable if
you run it manually and mis-type the host name.  I'll add a check to the
code.

Craig