Holger Parplies <wbppc AT parplies DOT de> wrote [Yesterday +0200]
HP > while I like the idea of being flexible about how to obtain the backup,
I
HP > don't see that you would need to modify the configuration at runtime for
HP > that to work. Maybe I'm missing something obvious, but I would imagine
either
That's because I need to tell BackupPC to contact another host (rather
than the actual virtual machine that is turned off) that has access to the
NetStorage disks.
HP >
HP > 1.) RsyncClientCmd could do all the work - simply point that to a script
HP > that sets things up and execs the appropriate 'ssh $host rsync ...'
HP > command.
No, I don't think so. I need to modify more things inside configuration.
I find it easier to reload config (4 lines of code inside BackupPC_dump)
than handling BackupPC perl variables inside a pre-backup command.
HP > 2.) DumpPreUserCmd could prepare things (as you are doing now) and
write into
HP > a state file whether a native or chroot backup should be done.
HP > RsyncClientCmd could be a script that reads that state file and
then execs
HP > the appropriate command like above.
Again, I need more modifications inside config file.
HP > 3.) DumpPreUserCmd *can* be Perl code, so you could probably even use it
HP > to do exactly what you are proposing *without* modifying the
BackupPC
HP > code (meaning if the change is not of general interest, you don't
need to
HP > patch the source to get its benefits; you can put it in the
HP > configuration) - if you really need it.
Well, maybe you're right at this point, but for me it's easier and faster
just reload configuration after DumpPreUserCmd
HP > You'll have to be smart about PingCmd in any case (probably just ping
the
HP > server holding the virtual disk contents?).
I just don't use PingCmd for this particular cases as it is the first
thing BackupPC runs. So if I turn off the virtual machine BackupPC would
try to ping the virtual machine and find out it's unreachable so it will
never begin the backup. And viceversa.
I need to check for the virtual machines status at DumpPreUserCmd or
whatever command BackupPC may run. But the main problem persists, because
if that command finds out that the virtual machine host is turned off and
config is prepared for a running machine I need to change the config
template for the host from this:
<template_on.pl>
$Conf{ClientNameAlias} = '_VIRTUALMACHINE_';
$Conf{BackupFilesExclude} = {
'*' => [
'/proc/*',
'/sys/*'
]
};
$Conf{XferMethod} = 'rsync';
$Conf{BlackoutPeriods} = [
{
'hourEnd' => '21.5',
'weekDays' => [
'1',
'2',
'3',
'4',
'5',
'6',
'7'
],
'hourBegin' => '7'
}
];
$Conf{PingMaxMsec} = '100';
$Conf{FullAgeMax} = '15';
$Conf{IncrAgeMax} = '15';
$Conf{PingCmd} = '';
$Conf{DumpPreUserCmd} = '/var/lib/backuppc/configure_vm_backuppc.sh
_VIRTUALMACHINE_';
</template_on.pl>
to this:
<template_off.pl>
$Conf{ClientNameAlias} = '_VIRTUALSERVER_';
$Conf{BackupFilesExclude} = {
'*' => [
_EXCLUDE_
]
};
$Conf{XferMethod} = 'rsync';
$Conf{BlackoutPeriods} = [
{
'hourEnd' => '21.5',
'weekDays' => [
'1',
'2',
'3',
'4',
'5',
'6',
'7'
],
'hourBegin' => '7'
}
];
$Conf{PingMaxMsec} = '100';
$Conf{FullAgeMax} = '15';
$Conf{IncrAgeMax} = '15';
$Conf{PingCmd} = '';
$Conf{RsyncClientCmd} = '$sshPath -q -x -l root $host $rsyncPath $argList+
vm=_VIRTUALMACHINE_';
# Restore disabled if _VIRTUALMACHINE_ is off
$Conf{RsyncClientRestoreCmd} = '';
$Conf{DumpPreUserCmd} = '/var/lib/backuppc/configure_vm_backuppc.sh
_VIRTUALMACHINE_';
$Conf{DumpPostUserCmd} = 'ssh -lroot _VIRTUAL_SERVER_ offvirtuals umount
_VIRTUALMACHINE_';
</template_off.pl>
HP > Aside from all that, can't you just run the backup in the chroot
environment
HP > regardless of whether the virtual machine is running? What kind of
HP > virtualization are we talking about?
Xen virtualization with NetStorage disks. When virtual machine is off
BackupPC should back it up from a server that has access to that
NetStorage that is always available to BackupPC. When it is turned on I
just can't mount the disk on another server as filesystem may become
corrupt.
HP > I'm not saying your approach doesn't work. It's just that, personally,
I'd
HP > find a solution which does not modify the configuration at runtime more
HP > readable (maintainable) and more resilient against errors.
I'm open to new suggests. Tell me how can I modify RsyncClientCmd once
BackupPC already started BackupPC_dump. Because that's what I really need
to change in runtime tha value of variables such as $host or $hostIP.
HP > I disagree. As I said, I don't see that it makes anything possible that
isn't
HP > already. It *does* add a failure case (if a narrow one) and unnecessary
work
HP > (if not much) for the vast majority of BackupPC installations. And it
could
HP > conceivably break installations if anyone should currently use
DumpPreUserCmd
HP > to modify his configuration and rely on it *not* taking immediate
effect (not
HP > that I'd expect that, but who knows?).
I cannot see that case of failure you are talking about. I guess the vast
majority of BackupPC users doesn't need to modify host configuration
within BackupPC_dump runtime.
Again, I cannot imagine a practical case in which anyone would like
BackupPC to wake up, run DumpPreUserCmd to modify its own BackupPC
config file and then expect new parameters not to be applied to the config
of the current backup proceess but in the next wakeup.
My intention is to easily add a config line
$Conf{DumpPreUserCmd} = '/var/lib/backuppc/configure_vm_backuppc.sh
_VIRTUALMACHINE_';
to each virtual machine BackupPC's configuration so I can easily configure
ignore-state
backups for new virtual machines. This way BackupPC server will always
backup virtual machines regardless of their power status.
Best Regards.
--
Marcos Lorenzo de Santiago
System administrator
marcos.lorenzo AT andago DOT com
ÁNDAGO INGENIERÍA
Tlf: +34 916 011 373 Álcalde Ángel Arroyo, 10, 1º
Mvl: +34 637 741 034 28904, Getafe, Madrid (Spain)
Fax: +34 916 011 372 www.andago.com
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