I asked about recovery strategies should a master server croak.
There are no canned strategies -- no way to promote a replica server to
master, for instance.
In theory, it should be possible to take recent file dumps and create a
server from them. And in theory, it could be possible to restore from a
recent backup. I haven't tried either to date. The key issue would be
whether or not current replica servers would survive the experience.
Thanks to Marc Gibian for thorough reponses to this and related issues.
--sk
Original post and responses follow:
To: sun-managers@ra.mcs.anl.gov
Subject: NIS+ root replica --> root master
It seems to me that once my master server is toast, I can't manage
my NIS+ domain anymore. Does anyone know differently?
-When the master is dead, the replicas still provide all
services to clients ... but I can't mod nor dump the NIS+ tables.
-When the master is dead, there is no way to convert (promote) a
replica to master.
Has anyone successfully recovered a master from backup? /var/nis,
/etc/.rootkey, and /etc/nsswitch.conf would seem to be the only needed
items. But it is not obvious to me what happens if /var/nis from backup
tape is "behind" /var/nis on a replica. In theory, time stamps should
allow the replica to bring the recovered master back in sync ... Has
anyone actually done this?
--sk
Stuart Kendrick
Network Services
FHCRC
Date: Wed, 13 Nov 1996 14:21:36 -0500
From: "Marc S. Gibian" <gibian@stars1.hanscom.af.mil>
To: sbk@fhcrc.org
Subject: Re: NIS+ root replica --> root master
You are correct that root replicas don't buy you as much as one might think
should your root master fail. I have been developing procedures/scripts and what
have you for my customer's product including the area of NIS+ management. One
case we care about is when a root master goes away without notice. I originally
thought that setting up root replicas would allow us to just convert a root
replica into the new root master. WRONG! You can't get there from here... the
procedure Sun makes available for converting a root replica into a root master
requires the original root master to be running, although even then the
procedure never has worked for us. I believe you CAN use the technique for
dumping NIS+ table contents to flat files, used for changing IP address of root
masters, to get checkpoints from which you can then create a new root master if
needed. We haven't had time to try this, but given that I have the IP change
working (for the root master) and it uses the same technique, I think it should
work (let me know if you try it).
Personally, I believe two critical shortcomings in NIS+'s implementation are:
1. No integral mechanism for changing IP addresses on servers. This CAN be done,
but only through a lengthy and error prone procedure (though I have it
encapsulated in a (huge) shell script).
2. No integral mechanism for converting a root replica into the root master.
Unfortunately, my customer has no software support, so I can not submit these as
problem reports to Sun.
-Marc
Marc S. Gibian
Telos Consulting Services phone: (617) 377-6350
PRISM/TFS email: gibian@stars1.hanscom.af.mil
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