[Samba] CTDB question about "shared file system"

Martin Schwenke martin at meltin.net
Sat Aug 8 06:52:45 UTC 2020

Hi Bob,

On Thu, 6 Aug 2020 06:55:31 -0400, Robert Buck <robert.buck at som.com>

> And so we've been rereading the doc on the public addresses file. So it may
> be we have gravely misunderstood the *public_addresses* file, we never read
> that part of the documentation carefully. The *nodes* file made perfect
> sense, and the point we missed is that CTDB is using floating
> (unreserved/unused) addresses and assigning them to a SECOND public
> interface (aliases). We did not plan a private subnet for the node traffic,
> and a separate public subnet for the client traffic.

> [...]

> Here is our mistake... The initial *public_addresses* file had identical
> addresses as the *nodes* file, containing the private IP addresses assigned
> by AWS. Not good, right? The error messages shown, above, were the result.

Yep, that would definitely cause chaos.  ;-)

CTDB is really designed to have the node traffic go over a private
network.  There is no authentication between nodes (other than checking
that a connecting node is listed in the nodes file) and there is no
encryption between nodes.  Contents of files will not be transferred
between nodes by CTDB if filenames are sensitive then they could be
exposed if they are not on a private network.

In the future we plan to have some authentication between nodes when
they connect.  Most likely a shared secret used to generate something
from the nodes file.

> [...]
> And after these changes the logs simply have these messages periodically:
> Disabling takeover runs for 60 seconds
> Reenabling takeover runs
> *Is this normal?*

How frequently are these messages logged?  They should occur as nodes
join but should stop after that.  If they continue are there any clues
indicating why takeover runs occurs?  A takeover run is just what CTDB
currently calls a recalculation of the floating IP addresses for

peace & happiness,

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