On Wed, Sep 25, 2013 at 3:58 AM, Kai Schaetzl maillists@conactive.com wrote:
First, I omitted to explicitely state that these are web servers. There is no dhcp, only one or, in a few cases, a few IP static IP addresses. Mostly Centos 5. Changing the data is *not* the problem. As already said this will mostly be done by replacing config files (cp -a, not mv, this assures it can be done even more than once without a problem, replacement operations in files always ask for trouble if something non-standard happens, not to mention one has to code this - it's easier just to provide the correct new files), and by reading in a sql command that replaces an IP address in some tables.
The big question is when and how to do this.
Why don't you just do it (except maybe the sql thing) before the shutdown? That is, instead of putting a script in place and changing something else to schedule a later run, just run it and be done. You probably already have a way to control them via ssh from a single location anyway - just run a script there that does them all at once close to shutdown time. The config file changes won't take effect until a reboot anyway. The sql change is more of a special case though. Unless you know all of the code involved, it's likely that some other components are going to read and cache the old values and not update after your change. I'd try to shut that box down last and make the change at the very end. Or make sure it starts first and has the new values before anything else can connect - otherwise you may have to restart the other components. If your sql command sets a field value where the old value matches your old addresses and there is no overlap in new/old ranges then it wouldn't hurt to run multiple times so you shouldn't have to be careful about that part..